phd thesis quantum entanglement

Graduate Thesis Or Dissertation

Quantum entanglement generation in trapped ions using coherent and dissipative methods public deposited.

• Entangled states are a key resource in fundamental quantum physics, quantum cryptography, and quantum computation. In this thesis, we focus on the demonstrations of two novel methods to generate entanglement. First, we implement dissipative production of a maximally entangled steady state on two trapped ions. Dissipative and coherent processes are combined and implemented in a continuous time-independent fashion, analogous to optical pumping of atomic states, continuously driving the system towards the steady entangled state. With this method, we obtain a Bell state fidelity up to 0.89(2). Second, we propose and demonstrate a novel coherent process to confine quantum evolution in a subspace between an initial separable state and the target entangled state. We demonstrate this scheme on two and three ions obtaining a Bell state fidelity up to 0.992(2). Both of these methods are robust against certain types of experimental noise and decoherence. Additionally, we demonstrate sympathetic cooling of ion chains to near the ground state of motion with an electromagnetically-induced-transparency (EIT) method. This results in roughly an order of magnitude faster cooling time while using significantly lower laser power compared to the conventional resolved sideband cooling method. These techniques may be helpful for scaled-up quantum computing.
• Lin, Yiheng
• Wineland, David J.
• Cornell, Eric
• Jonas, David
• Regal, Cindy
• Thompson, James
• University of Colorado Boulder
• trapped ion experiment
• quantum information
• quantum computing
• open quantum system
• quantum entanglement
• quantum optics
• Dissertation
• In Copyright
• English [eng]

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• Princeton University Doctoral Dissertations, 2011-2024

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• Published: 05 August 2021

High-performance quantum entanglement generation via cascaded second-order nonlinear processes

• Zichang Zhang 1 , 2 ,
• Chenzhi Yuan   ORCID: orcid.org/0000-0003-3275-335X 1 , 2 ,
• Si Shen 1 , 2 ,
• Hao Yu 1 , 2 ,
• Ruiming Zhang 1 , 2 ,
• Heqing Wang 3 ,
• You Wang 1 , 4 ,
• Guangwei Deng 1 , 2 , 5 ,
• Zhiming Wang 1 , 6 ,
• Lixing You   ORCID: orcid.org/0000-0001-7304-0474 3 ,
• Zhen Wang 3 ,
• Haizhi Song 1 , 4 ,
• Guangcan Guo 1 , 5 &
• Qiang Zhou   ORCID: orcid.org/0000-0001-7099-1995 1 , 2 , 5  

npj Quantum Information volume  7 , Article number:  123 ( 2021 ) Cite this article

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• Quantum optics
• Single photons and quantum effects

In this paper, we demonstrate the generation of high-performance entangled photon-pairs in different degrees of freedom from a single piece of fiber pigtailed periodically poled LiNbO 3 (PPLN) waveguide. We utilize cascaded second-order nonlinear optical processes, i.e., second-harmonic generation (SHG) and spontaneous parametric downconversion (SPDC), to generate photon-pairs. Previously, the performance of the photon-pairs is contaminated by Raman noise photons. Here by fiber-integrating the PPLN waveguide with noise-rejecting filters, we obtain a coincidence-to-accidental ratio (CAR) higher than 52,600 with photon-pair generation and detection rate of 52.36 kHz and 3.51 kHz, respectively. Energy-time, frequency-bin, and time-bin entanglement is prepared by coherently superposing correlated two-photon states in these degrees of freedom, respectively. The energy-time entangled two-photon states achieve the maximum value of CHSH-Bell inequality of S  = 2.71 ± 0.02 with two-photon interference visibility of 95.74 ± 0.86%. The frequency-bin entangled two-photon states achieve fidelity of 97.56 ± 1.79% with a spatial quantum beating visibility of 96.85 ± 2.46%. The time-bin entangled two-photon states achieve the maximum value of CHSH-Bell inequality of S  = 2.60 ± 0.04 and quantum tomographic fidelity of 89.07 ± 4.35%. Our results provide a potential candidate for the quantum light source in quantum photonics.

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Introduction.

Quantum correlated/entangled photon-pairs are serving as essential resources in quantum photonics, such as quantum key distribution (QKD) 1 , 2 , 3 , 4 , quantum teleportation 5 , 6 , 7 , quantum-enhanced metrology 8 , 9 , and linear optical quantum information processing (LOQC) 10 , 11 . Approaches, such as cascaded emissions in single-emitters 12 , 13 and spontaneous parametric processes 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , are developed to generate correlated/entangled photon-pairs. The latter one includes spontaneous parametric down conversion (SPDC) and spontaneous four-wave mixing (SFWM), already widely utilized in several applications 23 , 24 , 25 , 26 , 27 , 28 .

The correlated/entangled photon-pairs at 1.5 μm are important for long-distance quantum networks. The generation of 1.5 μm bright photon-pairs has been demonstrated via SPDC process in β -BaB 2 O 4 (BBO) 29 , 30 , periodically poled KTiOPO 4 (PPKTP) 31 , 32 , 33 , periodically poled LiNbO 3 (PPLN) 18 , 26 , 27 , 28 , 34 , 35 , 36 , 37 , 38 , and other second-order nonlinear optical materials 39 , 40 , or SFWM process in silica fiber 14 , 41 , 42 , 43 , 44 , 45 , silicon 15 , 16 , 25 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , silicon nitride 61 , 62 , chalcogenide glass 63 , and other third-order nonlinear optical materials 64 , 65 , 66 . While the second-order nonlinear process is in general more effective than the third-order one, it often requires a sophisticated optical system capable to simultaneously manipulate light at quite different wavelengths 67 . Fortunately, a scheme of cascaded second-harmonic generation (SHG) and SPDC processes with two 26 , 27 , 28 or a single waveguide 67 , 68 , 69 has been developed to generate photon-pairs with second-order nonlinear optical devices at 1.5 μm. However, the performance of such quantum light sources is limited by the spontaneous Raman scattering (SpRS) noise. Although the SpRS noise has been experimentally investigated in those sources 67 , the further endeavor to suppress such noise for high-performance quantum light sources has not yet been reported.

In this paper, we obtain high-performance entangled photon-pairs in different degrees of freedom by cascaded SHG/SPDC processes in a single piece of fiber pigtailed periodically poled LiNbO 3 (PPLN) waveguide. The SpRS noise photons are effectively eliminated by fiber-integrating the waveguide with noise-rejecting filters, i.e., fiber-based DWDMs. Photon-pairs with a coincidence-to-accidental ratio (CAR) higher than 52,600 are generated, with a generation rate and detection rate of 52.36 kHz and 3.51 kHz, respectively.

Entanglement in degrees of freedom of energy–time, frequency-bin, and time-bin are prepared by coherently superposing correlated two-photon states. The measured visibility of the Franson interference curve is 95.74 ± 0.86% for energy–time entanglement, indicating a maximum value of CHSH-Bell inequality of S  = 2.71 ± 0.02. The prepared frequency-bin entangled two-photon states are reconstructed with the fidelity of 97.56 ± 1.79% by observing the spatial two-photon quantum beating with visibility of 96.85 ± 2.46%. The time-bin entangled two-photon states achieve a maximum value of CHSH-Bell inequality of S  = 2.60 ± 0.04, and fidelity of 89.07 ± 4.35% measured via quantum-state tomography. Our results show that a high-performance quantum light source with cascaded second-order nonlinear processes on a photonics chip should be feasible.

PPLN waveguide module with noise-rejecting filters

Figure 1a shows the design of PPLN waveguide module with noise-rejecting filters which consists of a bandpass filter (F1), a PPLN waveguide, a bandstop filter (F2). Two fiber pigtails are used to connect the waveguide and the noise-rejecting filters. The cascaded SHG and type-0 SPDC process could take place in the PPLN waveguide with a pump light to generate the correlated/entangled photon-pairs. The PPLN waveguide only operates in a single polarization mode that is parallel with the polarization of pump light. The noise photons generated by the pump light before the input port of the module can be removed by F1 and the ones caused by the residual pump light output from the PPLN waveguide could be effectively eliminated by F2. In other words, the noise photons from SpRS process are only generated within the proposed PPLN waveguide module. In our design, the fiber pigtails connecting the PPLN waveguide and noise-rejecting filters are both 20-cm long—limited by our fabrication process, in which few SpRS noise photons could be generated. In principle, these SpRS noise photons could be further reduced by getting rid of fiber pigtails in a fully integrated scheme, for instance we can directly integrate F1 and F2 on both ends of the PPLN waveguide in the future.

a The design of the PPLN waveguide module. The input pump photons at λ p pass through the filter (F1), with the input noise photons removed. The SpRS process takes place in the two fiber pigtails, while the cascaded SHG/SPDC processes occur in the PPLN waveguide. After filter (F2), the residual pump light is smaller than the input one by about ~ 20 dB, which could reduce the SpRS noise photons by ~ 100 times in per unit length of the fiber. b Measured spectra of correlated photon-pairs with phase matching. c and d are the measured co- and cross-polarized Raman spectra in the PPLN waveguide module under the phase mismatching condition.

Table 1 gives main parameters of the PPLN waveguide module from HC Photonics. A piece of 50-mm long PPLN waveguide is fabricated by reverse proton exchange (RPE) procedure with a poled period of 19 μm. The normalized conversion efficiency of SHG process is 500 %·W –1 with pump light at 1540.46 nm. Two identical DWDMs with the central transmission wavelength at 1540.46 nm and bandwidth of ~ 200 GHz are used to reject the noise photons.

The single-photon level spectra of correlated photon-pairs and SpRS noise photons generated from the PPLN waveguide module are measured (see details in the spectra of noise and correlated photons in “Methods”). As shown in Fig. 1b , the correlated photon-pairs can be obtained in a broadband spectrum with a full width at half-maximum (FWHM) of ~ 60 nm, which are contaminated with different amounts of SpRS noise at different frequencies. Figure 1c shows the spectrum of co-polarized SpRS noise photons, which is quite distinct from the corresponding spectra in the pigtailed fiber (see Supplementary Note 3 ), while the spectrum of cross-polarized SpRS noise photons shown in Fig. 1d nearly has a similar profile with the corresponding spectrum in the pigtailed fiber (see Supplementary Note 3 ). This suggests that the SpRS noise photons are from both the fiber pigtails and the PPLN waveguide. A detailed investigation is given in Supplementary Note 2 .

Entanglement generation with PPLN waveguide module with noise-rejecting filters

Quantum entanglement in different degrees of freedom is prepared and characterized with the setups shown in Fig. 2a–e . Figure 2a shows the experimental setup for generating correlated/entangled photon-pairs. The PPLN waveguide module is pumped by either continuous wave (CW) or pulsed laser, which is selected by an optical switch in our experiment. For both cases, the pump power is amplified, attenuated, and monitored by an erbium-doped fiber amplifier (EDFA), variable optical attenuator (VOA), and 99:1 beam splitter (BS) with a power meter, respectively. A dense wavelength division multiplexer (DWDM) with the central transmission wavelength at 1540.46 nm and a passband width of ~125 GHz is employed to suppress the amplified spontaneous emission noise from the EDFA. The polarization state of the pump laser is manipulated by a polarization controller (PC). A polarization beam splitter (PBS) is used to ensure the polarization alignment for maximizing the efficiency of phase matching in the PPLN waveguide. The correlated/entangled photon-pairs are generated by cascaded SHG/SPDC processes. An isolator is connected to the output port of the module to reject the residual second-harmonic (SH) photons at 770 nm 70 . Figure 2b–e shows setups for characterizing the quantum correlation of the generated photon-pairs, for characterizing the performance of the energy–time 71 or time-bin entanglement 43 , 72 , 73 , for coherently manipulating two-photon state 45 , for preparing and measuring the frequency-bin entanglement 31 , 35 , 44 , 45 , respectively.

a Setup for preparing correlated/entangled photon-pairs. b Setup for characterizing correlated photon-pairs. c Setup for characterizing energy–time and time-bin entanglement. The synchronous signal is from AWG as shown in Fig. 2a. d Setup for coherently manipulating the energy–time-entangled two-photon state. e Setup for preparing and characterizing frequency-bin entangled photon-pairs. The λ p in Fig. 2a is 1540.46 nm and λ s,i  = 1531.72 nm, 1549. 34 nm in ( b – e ). IM intensity modulator, EDFA erbium-doped fiber amplifier, VOA variable optical attenuator, PC polarization controller, BS beam splitter, PBS polarization beam splitter, DWDM dense wavelength division multiplexer, PPLN periodically poled LiNbO 3 , UMZI unbalanced Mach–Zehnder interferometer, VODL variable optical delay line, AWG arbitrary waveform generator, TDC time to digital convertor, SNSPD superconducting nanowire single-photon detector.

Generation of the correlated photon-pairs

Correlated photon-pairs are generated with setups shown in Fig. 2a , in which a CW pump at 1540.46 nm is used. The generated photon-pairs are sent into setups in Fig. 2b , in which the signal and idler photons at 1531.72 and 1549.34 nm are obtained by using two DWDMs with a FWHM bandwidth of ~125 GHz, respectively. The signal and idler photons are detected by two superconducting nanowire single-photon detectors (SNSPDs, P-CS-6, PHOTEC, see Supplementary Note 6 ). A time to digital converter (TDC, ID900, ID Quantique) is used to record the counting rates of the signal and idler photons, and the coincidence events between them.

Figure 3a shows the measured counting rate of the signal photons under different levels of pump power, which are well fitted with a quadratic polynomial curve (black line). The quadratic (red line) and linear components (blue line) are corresponding to the contributions of generated photon-pairs and noise photons, respectively. It shows that the correlated photon-pairs generated in cascaded SHG/SPDC processes are dominant in the generated photons. Similar results are also obtained for idler photons (see Supplementary Fig. 1a ).

a Photon-counting rate (black circle) in signal channel versus pump power. The black solid line is the quadratic polynomial fitting curve of the photon-counting rate with the quadratic and linear parts shown as the red and blue curves, respectively. The error bars are estimated by Poissonian photon-counting statistics. b Measured CAR versus pump power. The error bars are estimated from the statistical errors of the coincidence and accidental coincidence counts, in which the former is obtained by assuming Poissonian statistics and the latter is estimated by the standard deviation values of accidental coincidence in three 300-ps time windows away from the coincidence peak. The inset is the coincidence histogram between signal and idler photons when the pump power is set at ~2 mW, and a coincidence window of 300 ps is marked. c Results of Franson interference for β  = −1.57 (red circle) and β  = −0.64 (blue rectangle). d Results of two-photon interference (red circle) and single-photon interference (blue rectangle). The error bars of coincidence count in ( c , d ) are estimated by repeating the measurement three times, while the error bars of photon counts in ( d ) are obtained by Poissonian photon-counting statistics.

Figure 3b shows the coincidence-to-accidental ratio (CAR) calculated by CAR =  C c / A cc under different levels of pump power, where C c and A cc are the coincidence count and accidental coincidence count, respectively. The inset of Fig. 3b shows a typically measured histogram with a pump power of ~2 mW, which is the accumulation of coincidence events in 20 s. The coincidence count is collected within a time window of 300 ps covering the coincidence peak, while the accidental coincidence count is estimated by the average of counts within three 300-ps time windows away from the coincidence peak (see Supplementary Fig. 1b ). The CAR reaches a maximum value of 52,600 when the pump power is 0.27 mW.

With the results of signal/idler photon-counting rate and their coincidence counts, we obtain the generation rate and collection efficiency of photon-pairs via calculation (see Supplementary Fig. 1c and d ). Finally, we can derive that our source achieves a photon-pair generation rate of 52.36 kHz with a CAR of 52,600, and 9.11 MHz with a CAR of 443. The calculated collection efficiencies of signal and idler photons are ~27% and ~ 23%, respectively, including the output efficiency of the PPLN module (~73%), the transmission efficiencies of isolator (~89%), and the DWDMs (~67%), as well as the detection efficiency of SNSPDs (~65%).

Performance of energy–time entanglement

The correlated photon-pairs generated in SFWM or SPDC process are naturally energy–time entangled when CW pump light is used meanwhile has coherent time longer than the generated photons after filters 74 . This type of entanglement has considerable potential in high-dimensional quantum key distribution (QKD) 75 . In our experiment, the generated photon-pairs under the CW pump are sent into setups in Fig. 2c to characterize the energy–time entanglement by the Franson interference 71 . In Fig. 2c , the signal and idler photons are first separated by DWDMs, and then pass through two unbalanced Mach–Zehnder interferometers (UMZIs, MINT, Kylia), respectively. The time delay difference between the long and short arms is 625 ps in both UMZIs, while an additional phase difference α or β between the two arms can be tuned by applying a voltage on a piezo actuator. In the experiment, we stabilize the phase of UMZI by using a feedback system (see the details in Supplementary Method ). The photons from each output port of the UMZIs are detected by SNSPDs and the corresponding photon counts are recorded by the TDC.

In our experiment, three peaks appear in the coincidence measurement between signal and idler photons output from the port A 1 and B 1 in the UMZIs shown in Fig. 2c , respectively. To observe the Franson interference 71 , we select the coincidence counts in the central peak with a time window of 300 ps when the phase differences α and β are scanned and fixed, respectively. As shown in Fig. 3c , when β  = −0.64 rad and −1.57 rad, the coincidence counts versus α can be well fitted with a cosine function showing visibilities of 95.74 ± 0.86% and 93.55 ± 3.15%, respectively, without subtracting the accidental coincidence counts. The deviation of the visibility from the unit can be attributed to the accidental coincidence, the unbalanced loss and imperfect beam splitting in the UMZIs, and the frequency instability of the pump laser. On the other hand, the signal and idler photon-counting rates are almost unchanged during the measurement, indicating that the fringes in Fig. 3c are the results of the quantum interference of the energy–time entangled two-photon state. The two curves shown in Fig. 3c can be utilized to further verify the violation of CHSH-Bell inequality for the energy–time entanglement 72 . The minimum visibility of violation of the Bell inequality is 70.7%, and so the Bell inequality is violated by 35 and 7 standard deviations when β  = −0.64 rad ( S  = 2.71 ± 0.02) and −1.57 rad ( S  = 2.65 ± 0.09), respectively. Compared with a recent work 76 , our results represent higher visibility of the Franson interference.

With the setups shown in Fig. 2d , we coherently manipulate the energy–time entangled two-photon state by sending it into a single UMZI (see Supplementary Note 4 ). The coherent manipulation can prepare a superposition state of spatial bunched and anti-bunched path-entangled states, and the complex superposition coefficients of the two states can be fully manipulated by the additional phase φ in the UMZI. The spatial bunched path-entangled state is measured by the coincidence measurement between signal and idler photons from one output of the UMZI 45 , which is shown by the red circles in Fig. 3d . We can see that such coincidence shows cosinoidal oscillation with visibility of 94.58 ± 0.63% when the phase φ changes, indicating that the prepared state converts between the spatial bunched and anti-bunched path-entangled states. An attenuated CW laser is also injected into the UMZI shown in Fig. 2d and its single-photon interference is observed, the fringe of which is shown by the rectangle curves in Fig. 3d and has a visibility of 98.10 ± 0.01%. It is obvious that the period of the oscillation of coincidence between signal and idler photons is half that of the observed single-photon interference. Such difference verifies that our coherent manipulation of energy–time entangled state is based on the interference of matter-wave of the entangled two-photon state.

Generation of frequency-bin entanglement

Frequency-bin entanglement attracts much attention due to its potentials in quantum information processing 17 , 77 . In our scheme, we can obtain frequency-bin entanglement by coherently manipulating the energy–time entanglement 45 . As shown in Fig. 2e , the generated energy–time entangled photon-pairs are directly sent into a single UMZI, by setting the additional phase φ  =  π to prepare the photon-pairs to a spatial anti-bunched path-entangled state which is exactly a frequency-bin entangled state. The frequency-bin entanglement is characterized by the spatial quantum beating 31 , 44 , 45 . The two-photon state output from the UMZI is injected into a 50:50 BS with a relative arrival time delay τ between the two paths which is controlled by a VODL (variable optical delay line). To ensure the input photons of BS are in an identical polarization state, PCs and PBSs along the two optical paths are used. At the output ports of the 50/50 BS, signal and idler photons are selected by two DWDMs and are detected by SNSPDs, respectively.

Figure 4a shows the result of the spatial quantum beating. When the delay time τ is changed, the coincidence counts between signal and idler photons show modulated cosinoidal oscillation, i.e., a clear signature of frequency-bin entanglement 31 , 44 , 45 . The experimental data in Fig. 4a can be fitted by an expression (see Supplementary Note 4 )

where Δ τ  =  τ − τ 0 with τ 0 being the intrinsic time delay between signal and idler photons; C 0 is a constant; V is the visibility; sinc( Ω ·Δ τ ) describes the envelope of the spatial quantum beating and it is associated with the transmission spectra of DWDMs in Fig. 2e , approximated by a rectangular function with an angular frequency bandwidth of Ω ; Δ ω si is the difference between the central angular frequencies of the detected signal and idler photons. The fitting gives Ω  = 2π × (116.35 ± 2.20) × 10 9 rad·s −1 and Δ ω si  = (2.22 ± 0.01) × 10 12 rad·s −1 which agree well with the transmission bandwidth of 125 GHz and central wavelength of 1531.72 nm (1549.34 nm) of the DWDM for signal (idler) photons in our experiment. We also get V  = 96.85 ± 2.46% and phase φ  = 0.18 ± 0.06 rad. According to the method in Refs. 31 and 78 , the density matrix of the frequency-bin entangled state can be reconstructed by experimental measurements (see details in the reconstruction of frequency-bin entangled state in “Methods”). Figure 4 b and c shows the real and imaginary parts of the reconstructed density matrix, which gives a target-state fidelity of 97.56 ± 1.79% with respect to the maximally entangled state \(\left| \psi \right\rangle = (\left| {\omega _s} \right\rangle \left| {\omega _i} \right\rangle + \left| {\omega _i} \right\rangle \left| {\omega _s} \right\rangle )/\sqrt 2\) . Our result demonstrates that the frequency-bin entanglement has been successfully prepared based on cascaded SHG/SPDC processes. It is worth noting that in our experiment only a pair of frequency bins is selected, i.e., the frequency-bin entanglement 78 , which can be further prepared to an entangled frequency comb by using comb-like filters 77 , 79 .

a Spatial quantum beating of frequency-bin entangled state. b , c The real and the imaginary parts of the experimentally reconstructed density matrix of frequency-bin entangled photon-pairs, respectively. d The phase α  +  β dependence of the threefold coincidence between the synchronous electrical signal and the photons from the ports A 1 &B 1 (red rectangle), A 1 &B 2 (blue triangle), A 2 &B 1 (purple inverted triangle), or A 2 &B 2 (green circle). e Correlation coefficient E ( α,β ) calculated from the four curves in d according to Eq. ( 2 ). f , g The real and the imaginary parts of the density matrix of time-bin entangled photon-pairs, respectively. The error bars in a and d are all estimated from measurement results assuming Poissonian statistics, while the error bars in e are obtained via propagation of statistical errors according to Eq. ( 2 ).

Generation of time-bin entanglement

Time-bin entanglement is suitable for many types of quantum information applications involving long-distance fiber-based transmissions of photons 72 . The photons entangled in time-bin can be created when periodically repeated double pulses (see the preparation of double-pulsed pump light in “Methods” for details) are used to pump the PPLN waveguide module in Fig. 2a . The performance of the generated time-bin entanglement also can be characterized by the experimental setup shown in Fig. 2c . In this case, all the four output ports in the two UMZIs, namely, A 1 , A 2 , B 1 , and B 2 are used.

The UMZI can project the time-bin qubit onto the time or energy bases when the time delay difference between the long and short arms of UMZI is equal to the interval of time-bins 43 . To select different bases, a synchronous electrical signal accompanying the generation of the double-pulsed pump light is introduced 72 . The Franson interference of time-bin entanglement can be observed by measuring coincidence between the projections of signal photon and idler photon on their energy bases. Figure 4d shows the threefold coincidence counts in a time window of 300 ps between the synchronous electrical signal, and signal (A 1 or A 2 ) and idler (B 1 or B 2 ) photons when the phase α in one UMZI is fixed and β in another UMZI is scanned. The coincidence counts involving the port combinations of A 1 &B 1 , A 1 &B 2 , A 2 &B 1 , and A 2 &B 2 all show remarkable interference fringes, and the raw visibilities of them are 94.59 ± 2.43%, 92.12 ± 2.51%, 90.30 ± 2.36%, 94.05 ± 2.39%, respectively. Our results show that the time-bin entangled photon-pairs at 1.5 μm have been generated in our scheme, which can be applied in metropolitan quantum teleportation system 6 , 7 .

With those Franson interference fringes, the violation of CHSH-Bell inequality can be observed 72 . The correlation coefficient is defined as

where \(R_{A_iB_j}\) is the threefold coincidence counts involving the port combinations A i ( i  = 1, 2) and B j ( j  = 1, 2). According to the theory of Franson interference 71 , \(R_{A_iB_j}\) is proportional to 1 + (−1) i+j V cos( α  +  β ), where V is the visibility of the interference fringes. The correlation coefficient calculated by Eq. ( 2 ) can be derived as E ( α , β ) =  V cos( α  +  β ) with a raw visibility of 91.75 ± 1.30%. The maximum value of CHSH-Bell inequality can be obtained as \(S = 2\sqrt 2 V = 2.60 \pm 0.04\) , showing a violation of Bell inequality of up to 15 standard deviations.

The entanglement of the generated photon-pairs can be confirmed unambiguously by reconstructing the density matrix via quantum-state tomography 43 , 73 . As shown in Fig. 2c , we choose the output ports A 1 and B 1 from the two UMZIs and calculate the density matrix by projecting the time-bin entangled two-photon states onto 16 measurement bases (see quantum-state tomography of time-bin qubits in “Methods” for details). The coincidence counts obtained in the above projection measurements are summarized in Supplementary Note 5 . As a result, we obtain the following density matrix:

The real and imaginary parts of this matrix are shown graphically in Fig. 4 f and g , respectively, from which a fidelity of 89.70 ± 4.35% is obtained with respect to the state \(\left. {\left| {{\it{{\Phi}}}^ + } \right.} \right\rangle = \left( {\left. {\left| {11} \right.} \right\rangle + \left. {\left| {22} \right.} \right\rangle } \right)/\sqrt 2\) (|1〉 and |2〉 represent the qubit in early and late time-bins, respectively). The probable main causes of this limited fidelity include the imperfection in double-pulsed pump laser, such as nonuniform pulse intensity, instable phase difference between double pulses, and limited extinction ratio, as well as the error in the calibration of the phase of the UMZIs.

In this paper, we demonstrated a high-performance entangled photon source. To show the performance of our entangled photon source, we compare the CAR and the raw detected photon-pair rate (DPPR) of our photon source with previous works in which various nonlinear optical media are employed 18 , 34 , 36 , 37 , 38 , 42 , 47 , 48 , 52 , 55 , 66 , 67 , 69 , 80 , 81 , as shown in Fig. 5a . The comparison shows that the performance of our entangled quantum light source has orders of magnitude improvement in DPPR (CAR) than other works under the same CAR (DPPR). Recently, the periodically poled thin-film lithium niobate (TFLN) nano-waveguides achieved a remarkable performance, better than more matured, macroscopic (nonintegrated) systems 38 . It could be useful for the future development of quantum photonic circuits using poled TFLN. Compared with this work, our source with the PPLN waveguide module can generate more photons by two orders of magnitude under the same CAR.

a A comparison of the CAR values and the detected photon-pair rate among the photon-pair sources in previous literature and our work. Ref. 80 is visible-telecom source, and others are all-telecom sources. The sources based on SFWM, SPDC, and cascaded SHG/SPDC processes are represented by triangles, rectangles and circles, respectively. b A scheme of a fully integrated structure for generating high-performance correlated/entangled photon-pairs by using cascaded SHG and SPDC processes. A inner waveguide is inserted between the SHG and SPDC regions to remove the residual pump light at 1.5 μm. c Setup for the spectra measurement of SpRS noise photons and correlated photon-pairs. The PBS used in this setup is a cube, rather than a fiber-coupled one, in order to avoid the dependence of splitting ratio on wavelength. d , e The pump power dependence of the noise photons at signal and idler wavelengths, respectively. All the error bars are estimated by Poissonian photon-counting statistics. f A set of typical histograms of two-fold and three-fold coincidence counts obtained in the quantum-state tomography of time-bin entanglement.

Two main properties of entangled quantum light sources, integratability and high-performance on the combination of CAR and DPPR, are required in quantum photonics. The cascaded SHG/SPDC processes can avoid working with photons at quite different wavelengths, which is favorable in integrated devices. In this paper, we further propose a more integrated and high-performance scheme, as shown in Fig. 5b . It is a TFLN waveguide structure with two sections connected with a high-pass intermediate waveguide with cutoff wavelength of around 1 μm. The SHG and SPDC processes occur in the two sections before and after the intermediate waveguide, the cutoff property of which at 1.5 μm band can effectively remove the SpRS noise photons generated before the waveguide structure and prevent the 1.5 μm pump light from pumping SpRS process in the coupling fiber after the waveguide structure.

Preparation of double-pulsed pump light

The double-pulsed pump light used in the generation of time-bin entanglement is prepared by externally modulating the CW light which is generated from a narrow-linewidth semiconductor laser (PPCL550, PURE Photonics). We apply an arbitrary waveform generator (AWG, 70002A, Tektronix) to generate a pulsed electrical signal. In order to obtain optical pulses with high extinction ratio, the electrical signal is amplified to identical to the V π of the lithium niobite intensity modulator (IM, GC15MZPD7813, CETC-44) by a microwave amplifier (SHF Communication Technologies AG, SHF S126 A). A 99:1 BS combined with a photodetector is used to generate a feedback signal in a controller, ensuring the IM works under an optimal bias voltage. Furthermore, for the generation of time-bin entangled photon-pairs, we utilize the AWG to generate a double-pulsed electrical signal with repetition frequency, pulse interval, and single pulse width of 100 MHz, 625 ps, and 125 ps, respectively.

The spectra of noise and correlated photons

To evaluate the SpRS noise photons and correlated photon-pairs from the PPLN waveguide module, the spectra of them were recorded by photon counting. As shown in Fig. 5c , the PPLN waveguide module is pumped by a CW laser, and a PC combined with a PBS is used to select the co-polarized photon and the cross-polarized photon. A tunable filter (XTA-50/U, EXFO) is applied before a SNSPD to select photons with different frequencies for detection. The SPDC process in our PPLN waveguide satisfies type-0 phase matching, i.e., the photo-pairs created are co-polarized with the pump light. In contrast, the polarization of the SpRS noise photons distributes over all orientations, in which the co-polarized component is larger than the cross-polarized one 82 . Thus, we can approximately assume that the directions of polarization with the highest and lowest photon-counting rates are corresponding to the co-polarized photon and the cross-polarized photon, respectively. Under the phase-matching condition, we measure the spectrum of co-polarized photons by tuning the central wavelength of the tunable filter and give the result in Fig. 1b . Then, under the phase mismatching condition, we measure the spectra of co- and cross-polarized photons with the same pump power level, as shown in Fig. 1 c, d , respectively. Figures 5 d, e show the counting rates of co-polarized photons in signal and idler channels under different levels of pump power, respectively. The photon-counting rates versus pump power in both Fig. 5 d, e can be fitted with linear functions. This indicates that the generation of correlated photon-pairs is suppressed under phase mismatching conditions. Thus, the spectra shown in Fig. 1 c, d correspond to the co- and cross-polarized SpRS noise photons, respectively. Considering that the photon-counting rates in Fig. 1b are much larger than those in Fig. 1c , we approximately regard the result shown in Fig. 1b as the spectrum of the correlated photon-pairs.

Reconstruction of the frequency-bin entangled state

Using the method in Refs. 31 and 78 , we can reconstruct the density matrix of the frequency-bin entangled state from experimental measurements and the expression is

It is obvious that the off-diagonal elements in Eq. ( 4 ) are determined by V and φ obtained via Eq. ( 1 ). Here, the diagonal element α has a meaning of the ratio of the state | ω s 〉| ω i 〉 in the frequency-bin entangled state, and it can be estimated by measuring the counting rate of signal and idler photons from the UMZI. In our experiment, α  = 0.502 ± 0.001 is obtained. The real and imaginary parts of the reconstructed density matrix are shown in Fig. 4 b, c , respectively.

Quantum-state tomography of time-bin entanglement

With the theory given in Ref. 43 , the projection measurements of a single time-bin qubit are implemented by passing through an UMZI with the time delay difference between the two arms equal to the time interval of time-bins. By injecting a time-bin qubit with state | ψ 0 〉 =  α |1〉+ β |2〉 ( \(\left| \alpha \right|^2 + \left| \beta \right|^2 = 1\) ) (|1〉 and |2〉 represent the qubit in early and late time-bins, respectively) into the UMZI and detecting photons from one output port of the UMZI, the photon could be observed possibly in three time slots. Photon detection at the first (third) slot corresponds to a projection of state onto|1〉 (|2〉), namely the “time basis”. Reversely, detection at the middle slot corresponds to a projection of state onto \((\left. {\left| 1 \right.} \right\rangle + e^{ - i\theta }\left. {\left| 2 \right.} \right\rangle )/\sqrt 2\) , which is “energy basis” depending on the additional phase difference θ between the two arms.

In order to obtain the density matrix of the time-bin entangled photon-pairs, quantum-state tomography must be implemented by 16 combinations of projection measurements between different bases (|1〉, |2〉, | D 〉, | R 〉) for signal and idler photons, where \(\left. {\left| D \right.} \right\rangle = (\left. {\left| 1 \right.} \right\rangle + \left. {\left| 2 \right.} \right\rangle )/\sqrt 2\) and \(\left. {\left| R \right.} \right\rangle = (\left. {\left| 1 \right.} \right\rangle + i\left. {\left| 2 \right.} \right\rangle )/\sqrt 2\) . Figure 5f shows some typical raw data in these projection measurements. When the additional phase differences α and β in the UMZIs in Fig. 2c are both set at 0, twofold coincidence between photons from the ports A 1 and B 1 in Fig. 2c are measured, and five distinguishable peaks appear in the coincidence histogram shown in Fig. 5f(i) 72 , which correspond to the projection on single basis or the sum of projections on different bases. The three middle peaks in the Fig. 5f(i) can further split into two or three peaks corresponding to the projection on single basis, when three-fold coincidence is implemented between the coincidence events in these peaks and the synchronous electrical signal, as shown in Fig. 5f(ii, iii, iv) . As a consequence, we obtain the two-photon projection measurements on the following bases simultaneously: |11〉, |12〉, |1 D 〉, |21〉, |22〉, |2 D 〉, | D 1〉, | D 2〉, and | DD 〉. In a similar way, we can perform the two-photon projection measurements on other bases by setting the α and β at 0&π/2, π/2&0, and π/2&π/2.

Data availability

All the data and calculations that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

The code used to generate data will be made available to the interested reader upon reasonable request.

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Acknowledgements

The authors thank Prof. Z.Z. Wang and Mr. Q.Z. Cai for the helpful discussions. This work is partially supported by National Key Research and Development Program of China (Nos. 2018YFA0307400, 2019YFB2203400, 2017YFA0304000, 2018YFA0306102, and 2017YFB0405100); National Natural Science Foundation of China (Nos. 61775025, 62075034, 12074058, 91836102, U19A2076, 61405030, 61704164, and 62005039); Sichuan Science and Technology Program (No. 2018JY0084); Open-Foundation of Key Laboratory of Laser Device Technology, China North Industries Group Corporation Limited (KLLDT202008).

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Zichang Zhang, Chenzhi Yuan, Si Shen, Hao Yu, Ruiming Zhang, You Wang, Guangwei Deng, Zhiming Wang, Haizhi Song, Guangcan Guo & Qiang Zhou

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Q.Z. convinced and supervised the project. Z.Z. and H.Y. under the supervision of Q.Z. and Z.W, and C.Y. under the supervision of G.G. performed the experiment and data analysis. S.S. and R.Z. under the supervision of H.S. and Y.W. developed the feedback system for generating pulsed pump light and the temperature control system for the PPLN module. H.W., H.L., L.Y., and Z.W. developed and maintained the SNSPDs used in the experiment. All authors participated in discussions of the results. Q.Z., Z.Z., and C.Y. prepared the manuscript with assistance from all other co-authors. All authors have given approval for the final version of the manuscript.

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Zhang, Z., Yuan, C., Shen, S. et al. High-performance quantum entanglement generation via cascaded second-order nonlinear processes. npj Quantum Inf 7 , 123 (2021). https://doi.org/10.1038/s41534-021-00462-7

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Choi, Kyung Soo (2011) Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9T7P-2C53. Quantum networks are composed of quantum nodes which coherently interact by way of quantum channels. They offer powerful capabilities for quantum computation, communication, and metrology. A generic requirement for these realizations is the capability to generate and store quantum states among multiple quantum nodes, and to disseminate these resources throughout the network via the quantum channels. In this thesis, I describe a series of experiments whereby single excitations in atomic ensembles are strongly coupled to optical modes and provide efficient means for the coherent control of entangled states between matter and light. By following the seminal proposal by Duan et al., we have generated measurement-induced entanglement of an excitation between two cold atomic ensembles. Using this system, we investigated the relationship for the global bipartite entanglement and local correlations in its subsystems. In addition, we achieved functional quantum nodes for entanglement distribution. Two pairs of remote ensembles at two quantum nodes were prepared into entangled states in a heralded and asynchronous fashion by the conditional controls of the entanglement. The quantum states of the ensembles were then distributed into polarization entangled states of photons. We also prepared an analogous quantum state and transferred the nonlocal coherence between two pairs of heralded entangled atomic ensembles, providing a step towards entanglement connection. Beyond such probabilistic approaches, we demonstrated an experiment where entanglement between two quantum memories is created by the reversible and deterministic mapping of an entangled state of light via dynamic electromagnetically induced transparency. This experiment opens novel prospects of integrating hybrid quantum systems by way of reversible quantum interfaces between light and matter. Then, we extended our work to multipartite quantum systems. We theoretically investigated the characterization of multipartite mode-entangled states by way of quantum uncertainty relations, and introduced theoretical tools to verify the entanglement orders in multipartite systems. In particular, we achieved entanglement for one delocalized photon among multiple optical modes (N > 2). Finally, we have achieved measurement-induced entanglement of spin waves among four quantum memories. The individual atomic components for the entangled W state of the four ensembles were then coherently converted into four propagating entangled beams of light via superradiant emissions. We observed the statistical and dynamic transitions for the multipartite entangled spin waves. Experiments described in this thesis thereby represent significant advances of experimental and theoretical capabilities to generate, store, transfer, and characterize entanglement of matter and light over quantum networks. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: Quantum network; Quantum communication; Quantum computation; Quantum information science; Entanglement; Coherent control; Atomic ensemble; Collective interaction; Electromagnetically induced transparency; Superradiance; Dicke states Degree Grantor: California Institute of Technology Division: Physics, Mathematics and Astronomy Major Option: Physics Thesis Availability: Public (worldwide access) Research Advisor(s): Thesis Committee: Defense Date: 25 May 2011 Other Numbering System: Other Numbering System Name Other Numbering System ID Kyung 114 Thesis Files Repository Staff Only: item control page Oxford Thesis Collection CC0 version of this metadata Entanglement between nodes of a quantum network Quantum devices are rapidly gaining momentum as a technology that will induce a paradigm shift in computing, communication and cryptography. Trapped ion qubits are one of the leading candidates for implementing a quantum computer, having previously demonstrated all of the required criteria. Local gate fidelities between ions exceed those for all other platforms, but the total number of ions in a trap is limited by unavoidable issues – one possibility for scaling the ion trap quantum proce... Email this record Please enter the email address that the record information will be sent to. Please add any additional information to be included within the email. Cite this record Chicago style, access document. ljs_thesis_final.pdf (Dissemination version, pdf, 33.4MB) Why is the content I wish to access not available via ORA? Content may be unavailable for the following four reasons. Version unsuitable We have not obtained a suitable full-text for a given research output. See the versions advice for more information. Recently completed Sometimes content is held in ORA but is unavailable for a fixed period of time to comply with the policies and wishes of rights holders. Permissions All content made available in ORA should comply with relevant rights, such as copyright. See the copyright guide for more information. Clearance Some thesis volumes scanned as part of the digitisation scheme funded by Dr Leonard Polonsky are currently unavailable due to sensitive material or uncleared third-party copyright content. We are attempting to contact authors whose theses are affected. Alternative access to the full-text Request a copy. We require your email address in order to let you know the outcome of your request. Provide a statement outlining the basis of your request for the information of the author. Please note any files released to you as part of your request are subject to the terms and conditions of use for the Oxford University Research Archive unless explicitly stated otherwise by the author. Contributors Bibliographic details, item description, related items, terms of use, views and downloads. If you are the owner of this record, you can report an update to it here: Report update to this record Report an update We require your email address in order to let you know the outcome of your enquiry. Login Admin eTheses Home Depositing eTheses About Nottingham eTheses Nottingham ePrints (2013) PhD thesis, University of Nottingham. A central aim of the field of relativistic quantum information (RQI) is the investigation of quantum information tasks and resources taking into account the relativistic aspects of nature. More precisely, it is of fundamental interest to understand how the storage, manipulation, and transmission of information utilizing quantum systems are influenced by the fact that these processes take place in a relativistic spacetime. In particular, many studies in RQI have been focused on the effects of non-uniform motion on entanglement, the main resource of quantum information protocols. Early investigations in this direction were performed in highly idealized settings that prompted questions as to the practical accessibility of these results. To overcome these limitations it is necessary to consider quantum systems that are in principle accessible to localized observers. In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such as quantum teleportation. We study cavities in (1+1) dimensions undergoing non-uniform motion, consisting of segments of uniform acceleration and inertial motion of arbitrary duration that allow the involved velocities to become relativistic. The transitions between segments of different accelerations can be sharp or smooth and higher dimensions can be incorporated. The primary focus lies in the Bogoliubov transformations of the quantum fields, real scalar fields or Dirac fields, confined to the cavities. The Bogoliubov transformations change the particle content and the occupation of the energy levels of the cavity. We show how these effects generate entanglement between the modes of the quantum fields inside a single cavity for various initial states. The entanglement between several cavities, on the other hand, is degraded by the non-uniform motion, influencing the fidelity of tasks such as teleportation. An extensive analysis of both situations and a setup for a possible simulation of these effects in a table-top experiment are presented. Item Type: Thesis (University of Nottingham only) (PhD) Supervisors: Fuentes, I. Adesso, G. Subjects: Faculties/Schools: UK Campuses > Faculty of Science > School of Mathematical Sciences Item ID: 13795 Depositing User: Date Deposited: 10 Feb 2014 10:42 Last Modified: 15 Dec 2017 09:49 URI: Available Versions of this Item Cavity mode entanglement in relativistic quantum information. (deposited 10 Feb 2014 10:42) [Currently Displayed] Actions (Archive Staff Only) Edit View Computer Algorithm Computer Science and Engineering Quantum Algorithms PhD thesis: Multipartite entanglement and quantum algorithms This person is not on ResearchGate, or hasn't claimed this research yet. Discover the world's research 25+ million members 160+ million publication pages 2.3+ billion citations No full-text available To read the full-text of this research, you can request a copy directly from the author. QUANTUM INF PROCESS Marc Bataille Alba Cervera-Lierta J PHYS A-MATH THEOR Luke Oeding J HIGH ENERGY PHYS Fernando Pastawski LETT MATH PHYS Ting-Chun Lin Isaac H. Kim Min-Hsiu Hsieh Mario Gaeta Jay Lawrence Hans J. Briegel Michael A. Horne Abner Shimony Philippe Grangier Gérard Roger R.C. Singleton J. I. de Vicente David Sauerwein Cornelia Spee Barbara Kraus B.S. Tsirelson Shahpoor Moradi Martin Hebenstreit INT J THEOR PHYS Richard P. Feynman Hannes Bernien A. E. Dréau J. Hadamard FORTSCHR PHYS Peter Stelmachovic Daniel M. Greenberger Anton Zeilinger D. Raghavarao G. H. Wannier PHYS LETT A Guruprasad Kar H. F. Trotter E. Schrödinger P. A. M. Dirac Elliott H. Lieb Mary Beth Ruskai G. Toulouse W. K. Wootters Marek Z-dotukowski MATH PROC CAMBRIDGE Erwin Schrödinger Raymond Laflamme Cesar Miquel Juan Pablo Paz J. von Neumann IBM J RES DEV Matthias Steffen David P. DiVincenzo Mark B. Ketchen Albert Einstein Boris Podolsky Nathan Rosen Guifre Vidal Bonafont Recruit researchers Join for free Login Email Tip: Most researchers use their institutional email address as their ResearchGate login Password Forgot password? Keep me logged in Log in or Continue with Google Welcome back! Please log in. Email · Hint Tip: Most researchers use their institutional email address as their ResearchGate login Password Forgot password? Keep me logged in Log in or Continue with Google No account? Sign up Faculty of Arts and Sciences FAS Theses and Dissertations Communities & Collections By Issue Date FAS Department Quick submit Waiver Generator DASH Stories Accessibility COVID-related Research Terms of Use Privacy Policy By Collections By Departments Symmetry, Topology and Entanglement in Quantum Many-Body Systems Citable link to this page Collections. FAS Theses and Dissertations [6566] Contact administrator regarding this item (to report mistakes or request changes) Show Statistical Information Trapped Ion Quantum Information CHRISTOPHER MONROE, Principal Investigator. University of Maryland Department of Physics, Joint Quantum Institute, and Center for Quantum Information and Computer Science University of Maryland Engineering a Control System for a Logical Qubit-Scale Trapped Ion Quantum Computer, Andrew Risinger, Ph.D Electrical and Computer Engineering (2022) Non-Integrable Dynamics in a Trapped-Ion Quantum Simulator , Patrick Becker, Ph.D. Physics (2021) Simulating many-body quantum spin models with trapped ions , Antonis Kyprianidis, Ph.D. Physics (2021) Experimental Study of Quantum Algorithms on Ion-trap Quantum Computers , Daiwei Zhu, Ph.D. Electrical and Computer Engineering (2021) Design and Construction of a Three-Node Quantum Network , Allison Carter, Ph.D Physics (2021) Scaling Quantum Computers with Long Chains of Trapped Ions , Laird Egan, Ph.D. Physics (2021) Cryogenic Trapped-Ion System for Large-Scale Quantum Simulation , Wen Lin Tan, Ph.D.Physics (2021) Mixed-Species Ion Chains for Quantum Networks , Ksenia Sosnova, Ph.D. Physics (2020) Construction, Optimization, and Applications of a Small Trapped-Ion Quantum Computer , Kevin Landsman, Ph.D. Electrical Engineering (2019) High Purity Single Photons Entangled with Barium Ions for Quantum Networking , Clayton Crocker, Ph.D. Physics (2019) Building and Programming a Universal Ion Trap Quantum Computer , Caroline Figgatt, Ph.D. Physics (2018) Demonstration of a Quantum Gate with Ultrafast Laser Pulses , Jamie David Wong Campos, Ph.D. Physics (2017) A Scanning Transfer Cavity Frequency Lock for Experimental Quantum Information , Katherine S. Collins, B.S. Physics (2017). Manipulation of the Quantum Motion of Trapped Atomic Ions via Stimulated Raman Transitions , Kenneth Wright, Ph.D. Physics (2017) Multi-Species Trapped Atomic Ion Modules for Quantum Networks , I. Volkan Inlek, Ph.D. Physics (2016) A Programmable Five Qubit Quantum Computer using Trapped Atomic Ions , Shantanu Debnath, Ph.D. Physics (2016). Experiments with Trapped Ions and Ultrafast Laser Pulses , Kale Johnson, Ph.D. Physics (2016). Quantum Thermalization and Localization in a Trapped Ion Quantum Simulator , Jacob Smith, Ph.D. Physics (2016) Engineering a Quantum Many-Body Hamiltonian with Trapped Ions, Aaron C. Lee, Ph.D. Physics (2016) A Modular Quantum System of Trapped Atomic Ions, David Alexander Hucul, Ph.D. Physics (2015) Dynamics and Excited States of Quantum Many-Body Spin Chains with Trapped ions , C. R. Senko, Ph.D. Physics (2014). Quantum information processing with trapped ion chains , T. Andrew Manning, Ph.D. Physics (2014). Ultrafast Control of Spin and Motion in Trapped Ions , Jonathan Albert Mizrahi, Ph.D. Physics (2013). Quantum Simulations of the Ising Model: Devil’s Staircase and Arbitrary Lattice Proposal , Simcha Korenblit, Ph.D. Physics (2013). Remote and Local Entanglement of Ions with Photons and Phonons , David Lee Hayes, Ph.D. Physics (2012). Quantum Simulation of Interacting Spin Models with Trapped Ions , Kazi Rajibul Islam, Ph.D. Physics (2012). Ytterbium Ion Qubit State Detection on an ICCD Camera , Aaron Lee, B.S. Physics (2012). Enhanced Light Collection from Single Trapped Ions , Jonathan Sterk, Ph.D. Physics (2011). State Detection of a Trapped Ion Qubit Using Photon Arrival Times , Kenny W Lee, B.S. Physics (2011). Quantum Teleportation Between Distant Matter Qubits , Steven Olmschenk, Ph.D. Physics (2009). Doppler-Free Spectroscopy of Iodine at 739nm , Andrew Chew, B.S. Physics (2008). University of Michigan Detection and Control of Individual Trapped Ions and Neutral Atoms , Mark Acton, Ph.D. Physics (2008). Implementation of Grover’s Quantum Search Algorithm with Two Trapped Ions , Kathy-Anne Brickman, Ph.D. Physics (2007). Remote Entanglement of Trapped Atomic Ions , David Moehring, Ph.D. Physics (2007). Fabrication and Characterization of Semiconductor Ion Traps for Quantum Information Processing , Daniel Stick, Ph.D. Physics (2007). Advanced Ion Trap Development and Ultrafast Laser-Ion Interactions , Martin Madsen, Ph.D. Physics (2006). Operation of a Two-Dimensional Ion Trap Array for Scalable Quantum Computation , David Hucul, B.S. Physics (2006). The Design and Implementation of Atomic Ion Shuttling Protocols in a Multi-Dimensional Ion Trap Array , Mark Yeo, B.S. Physics (2006). Controlled Coherent Excitations in a Single Cadmium Ion with an Ultrafast Laser , R. N. Kohn, Jr., B. S. Physics (2006). Cooling and Heating of the Quantum Motion of Trapped Cadmium Ions , Louis Deslauriers, Ph.D. Physics (2006). Quantum Information Processing with Two Trapped Cadmium Ions , Patricia Lee, Ph.D. Physics (2005). An Apparatus for the Observation of Trapped Cadmium Ion Interactions with Intense Laser Pulses , Russell Miller, B.S. Physics (2003). Skip to main content Accessibility information Enlighten Enlighten Enlighten Theses Latest Additions Browse by Year Browse by Subject Browse by College/School Browse by Author Browse by Funder Login (Library staff only) In this section Quantum entanglement of the spatial modes of light Jack, Barry (2012) Quantum entanglement of the spatial modes of light. PhD thesis, University of Glasgow. This thesis is a dissemination of the experimental work I have carried out in the last three and a half years, under supervision of Prof. Miles Padgett and Dr. Sonja Franke-Arnold. Presented within are seven unique experiments investigating the orbital angular momentum (OAM) states of light, and the associated spatial modes. Six of these experiments relate to measurements on quantum-entangled photon pairs produced in down-conversion. The first chapter of my thesis is a brief review of the some of the contributions made to the field of research of OAM, both involving classical and quantum states of light. This chapter introduces some of the hallmark experiments within the subject, from which my experimental work reported in this thesis is inspired. The second chapter details the set up of the down conversion experiment, and the experimental techniques used to design a fully functioning quantum measurement system. Most importantly, this includes the holographic techniques used to measure the spatial states of the photon pairs. In addition to holographic measurements, a system to holographically auto-align the down-conversion experiment was developed. Due to the sensitive nature of the experiments presented, this automated system has been crucial to the success of all of the single photon experiments presented within this document. The experimental results are split into three separate categories. The first (Chapter 3) describes measurements investigating the Fourier relationship between OAM and angular position states, both at the classical and quantum levels. The following chapter (Chapter 4) consists of four experiments designed to quantify the degree of entanglement of states of OAM and angular position. This includes the first demonstration of the historic EPR (Einstein-Podolsky-Rosen) paradox for OAM and angle states, violation of a Bell-type inequality for arbitrary OAM states, and characterisation of the density matrices for a range of OAM state-spaces. The final chapter (Chapter 5) reports a new type of ghost imaging using down-converted photon pairs. In this experiment, we violate a Bell inequality within a ghost image, demonstrating the entangled nature of our system and contributing a new element to the long standing contention over quantum vs. classical features within ghost imaging. These experiments have seen a wide range of collaboration. The experimental work on the Fourier relation on single photons was carried out in collaboration with Dr. Anand Kumar Jha (University of Rochester). The work on ghost imaging was performed with collaboration with Prof. Monika Ritsch-Marte (Innsbruck Medical University), and the angular EPR paradox work was carried out in collaboration with Prof. Robert Boyd (Univ. of Rochester) and Prof. David Ireland (Univ. of Glasgow). The work I present here is experimental, however any theoretical developments are in a large part due to the support of Dr. Sonja Franke-Arnold and Prof. Steve Barnett (Univ. of Strathclyde). Actions (login required) Item Type: Thesis (PhD) Qualification Level: Doctoral Keywords: Optics, Quantum Optics Subjects: > Colleges/Schools: > Supervisor's Name: Padgett, Prof. Miles Date of Award: 2012 Depositing User: Unique ID: glathesis:2012-3017 Copyright: Copyright of this thesis is held by the author. Date Deposited: 18 Nov 2011 Last Modified: 10 Dec 2012 14:02 URI: View Item Downloads per month over past year View more statistics The University of Glasgow is a registered Scottish charity: Registration Number SC004401 File(s) under embargo until file(s) become available Novel Quantum Devices and Innovative Simulation Methods for Quantum Engineering Degree grantor, degree level, degree name, committee member, thesis type, usage metrics. The Big Think Interview Your Brain on Money Explore the Library Will true AI turn against us? Do we have free will? Why are there conspiracy theories? Is religion helping or hurting us? Are we alone in the universe? Should we trust science? Michio Kaku Neil deGrasse Tyson Michelle Thaller Steven Pinker Ray Kurzweil Cornel West Helen Fisher Smart Skills High Culture The Present Hard Science Special Issues Starts With A Bang Perception Box Strange Maps The Learning Curve Everyday Philosophy Free Newsletters Memberships Quantum entanglement just got a whole lot weirder One of the most bizarre quantum phenomena ever discovered is that of quantum entanglement: where two particles both exist in a state where the properties of one depend on the other. You can’t measure a quantum particle’s state without determining its properties in the process, “breaking” the entanglement whenever you do so. Normally seen with identical particles, entanglement has just been demonstrated between particles with opposite charges, and leveraging that property has shown us an atom’s nucleus like never before. In the quantum Universe, things behave very differently than our common experience would suggest. In the macroscopic world we’re familiar with, any object we can measure appears to have intrinsic properties that are independent of whether we observe it or not. We can measure things like mass, position, motion, duration, etc., without worrying about whether that object is affected by our measurements; reality exists completely independently of the observer. But in the quantum world, that’s demonstrably not true. The act of measuring a system fundamentally changes its properties in an irrevocable way. One of the weirdest quantum properties of all is entanglement: where multiple quanta have inherent properties that are both indeterminate, but the properties of each one aren’t independent of the other. We’ve seen this demonstrated for photons, electrons, and all sorts of identical particles before, enabling us to test and probe the fundamental and surprising nature of reality. In fact, the 2022 Nobel Prize in Physics was awarded precisely for investigations into this phenomenon. But in a novel experiment, quantum entanglement has just been demonstrated between different particles for the first time , and already the technique has been used to see an atom’s nucleus like never before. In principle, quantum entanglement is a simple idea to understand, and it’s built on the idea of quantum indeterminism. Imagine you pull a ball out of a hat, and there’s a 50/50 chance that the ball has one of two properties. Perhaps it’s color: the ball could be black or white. Perhaps it’s mass: either you pulled out a light ball or a heavy ball. Perhaps it’s which direction it’s spinning: the ball could be “spin up” or “spin down.” If you only had one ball, you might wonder: upon pulling it out and examining the ball, did it always have those properties, even before you looked at it? Or did the ball have a set of indeterminate parameters, where it was a mix of: black-and-white, light-and-heavy, and spinning as a mix of both up-and-down, that was only determined at the instant you took the critical measurement? This is one of the key insights of quantum mechanics, as shown from famed experiments such as the double-slit experiment and the Stern-Gerlach experiment. Both of them are worth an explanation. If you take a barrier with two thin slits in it, what happens when you send a wave at it? The answer is easy: you get a wave-like pattern behind the barrier, where the parts of the wave that go through each slit interfere with one another, leading to a pattern of peaks-and-valleys on the other side. What happens if, instead, you send a series of particles at the barrier? The answer is again easy: you get a particle-like pattern behind the barrier, where particles either go through slit #1 or slit #2, and hence you get simply two piles on the other side. But in quantum mechanics, when you send quantum particles through the double slit, you get a wave-like pattern if you don’t measure which slit each particle goes through, but a particle-like pattern if you do make that measurement. This is true even if you send the quanta through one-at-a-time, as though they’re interfering with themselves. The act of observing — of making that critical measurement — and whether you do it or not is what determines which pattern you see. Reality, as we observe it, depends on what interactions do or do not take place prior to that critical observation. Similarly, the Stern-Gerlach experiment arises from passing quantum particles that possess an inherent property called “spin,” which means intrinsic angular momentum, through a magnetic field. These particles will either deflect aligned with the field or anti-aligned with the field: up or down, with respect to the field’s direction. If you try to deflect a particle whose spin has already been determined by passing through such a magnetic field, it won’t change: the ones that went up will still go up; the ones that went down will still go down. But if you pass it through a magnetic field with a different orientation — in one of the other two spatial dimensions — it splits again: left-right or forward-backward instead of up-and-down. What’s even weirder is now, once you’ve split it left-right or forward-backward, if you go and again pass it through an up-down magnetic field, it once again splits. It’s as though the last measurement you took erased any previous measurements, and with it, any definitive determination of the quantum state that existed in that dimension. This is a little bit of quantum weirdness, but it doesn’t have anything to do with entanglement just yet. Entanglement comes in when you have two or more particles that both exhibit some of this quantum indeterminism, but exhibit it together, in a way that’s linked. In an entangled quantum system, the quantum state of one particle is correlated with the quantum state of another. Individually, the quantum state of each one appears to be (and is measured to be) completely random. But if you take both quanta together, you’ll find that there are correlations that exist between the combined properties of both: something you couldn’t know if you only measured one of them. You can assume that either standard quantum mechanics applies, or that the state of both particles exists independent of whether they’re observed or not, and derive two different predictions. Part of 2022’s Nobel Prize in physics was for the demonstration that, when you actually perform these experiments and measure both quantum states, you find that the correlations are consistent only with standard quantum mechanics and not with the idea that the state of both particles exists independently of whether they’re observed or not. It’s for this reason that quantum entanglement is often described as spooky and counterintuitive. However, quantum entanglement experiments usually involve photons: the particles that light, electromagnetic radiation, is quantized into. The way that these entangled photons are created normally comes from passing a single photon through what’s called a down-conversion crystal, where one photon goes in and two photons come out. These photons have all the normal properties of regular photons — including spin, a wavelength defined by its energy, no electric charge, and all the standard quantum behavior that comes along with quantum electrodynamics — but will also have properties that are correlated between them: correlations that go beyond the quantum predictions of individual, isolated particles and are specific to entangled sets of particles. For a long time, this was the only way to perform experiments with entangled quantum particles: to have two particles that were identical in nature, i.e., that were the same species of quantum particle. But in an experimental first, a new kind of quantum entanglement has just been observed: entanglement between two fundamentally different particles that even have opposite electric charges ! In particle physics, you can produce new, heavy, unstable particles so long as you meet all the quantum requirements (i.e., you aren’t violating any conservation laws) and you also have enough energy (via Einstein’s E = mc² ) available for that particle to be created. From collisions involving protons and/or neutrons — i.e., quark-containing particles — the easiest particles to produce are known as mesons, which are quark-antiquark combinations. The lightest mesons, which involve only up, down, and strange quarks (and antiquarks), are: π particles (pions), which can be positively charged (up-antidown), negatively charged (down-antiup), or neutral (a superposition of up-antiup and down-antidown), K particles (kaons), which involve a strange quark (or antiquark) and either an up or down antiquark (or quark), η particles (etas), which involve a mix of up-antiup, down-antidown, and strange-antistrange quarks, and ρ particles (rhos), which — along with ω (omega) particles — are made of up-and-down quarks and antiquarks, but have their spins aligned rather than anti-aligned as for the other mesons. These are the only mesons that are lighter than the proton (and neutron), and are responsible for carrying the nuclear force within an atomic nucleus. They’re all short-lived and will all decay into lighter particles, but while the neutral pion (π 0 ) particle always decays into two photons, the neutral rho (ρ 0 ) particle always decays into both a positively charged (π + ) and a negatively charged (π – ) pion. It might not surprise you to learn that some of the properties of the photons that arise from neutral pion decays can be entangled: photons are identical particles and these two arose from the decay of a single quantum particle. But the shocking discovery that was just made was that the two charged pions that arise from a neutral rho decay are also entangled, marking the first discovery of two distinct, non-identical particles to display entanglement properties. Particles like pions and rhos can emerge not only from the collisions of two protons with one another, but also energetic-enough near-misses, simply from the interactions of the gluon fields of these two protons. The way the entanglement was identified was brilliant: when two rho particles are created in the atomic nuclei of two adjacent protons, they each decay into those two charged pions almost immediately. Because they’re so close together in space, the two positively charged (π + ) pions and the two negatively charged (π – ) pions each interfere with one another, making their own superposition and their own wavefunction. The interference patterns observed between the positively and negatively charged pions are the key evidence that reveal the inescapable but bizarre conclusion: the oppositely charged pions produced in each rho particle’s decay — the π + and the π – —must be entangled with one another. These observations were only possible because the rho particles that are produced are so astoundingly short-lived: with a mean lifetime of only 4 yoctoseconds, or 4 septillionths of a second. Even at the speed of light, these particles would decay very quickly compared to the distances between them, enabling the overlap of the pion wavefunctions to be substantial. Best of all, this new form of entanglement resulted in an immediate application: to measure the radius and structure of the heavy atomic nuclei that were almost (but not quite) collided with one another in these experiments. The spin-interference pattern that arose came from the overlap of these two wavefunctions, allowing the researchers to determine what the radius was to describe the interactions of the gluon fields from each atomic nucleus, for both gold (Au-197) and uranium (U-238). The results, of 6.53 ± 0.06 fm for gold and 7.29 ± 0.08 fm for uranium, are remarkably both larger than the radius you’d expect from measurements each nucleus using electric charge properties. For the first time, an experiment was able to demonstrate that it isn’t just identical quantum particles that can become entangled, but particles with opposite electric charges, too. (The π + and the π – , for what it’s worth, are one another’s antiparticle.) The technique of passing two heavy nuclei very close to one another at nearly the speed of light allows for photons, arising from the electromagnetic field of each nucleus, to interact with the other nucleus, occasionally forming a rho particle that decays into two pions. When both nuclei do this at once, the entanglement can be seen, and the radius of the atomic nucleus can be measured. It’s also remarkable that measuring the size of the nucleus through this method, which uses the strong force rather than the electromagnetic force, gives a different, larger result than one would get by using the nuclear charge radius. As lead author on the study, James Brandenburg, put it, “Now we can take a picture where we can really distinguish the density of gluons at a given angle  and  radius. The images are so precise that we can even start to see the difference between where the protons are and where the neutrons are laid out inside these big nuclei.” We now have a promising method to probe the internal structure of these complex, heavy nuclei, with more applications, no doubt, soon to come. Bruno De Souza Leao Torres PhD Thesis Defense Aspects of quantum information in quantum field theory: particle detector models, entanglement, and complexity. Supervisors: Dr. Eduardo Martin-Martinez, Dr. Beni Yoshida Current students , Current undergraduate students , Current graduate students , Thesis defence Reliability Function of Quantum Information Decoupling via the Sandwiched Rényi Divergence Published: 23 June 2024 Volume 405 , article number  160 , ( 2024 ) Cite this article Ke Li   ORCID: orcid.org/0000-0002-3944-8449 1 & Yongsheng Yao 1 , 2   45 Accesses Explore all metrics Quantum information decoupling is a fundamental quantum information processing task, which also serves as a crucial tool in a diversity of topics in quantum physics. In this paper, we characterize the reliability function of catalytic quantum information decoupling, that is, the best exponential rate under which perfect decoupling is asymptotically approached. We have obtained the exact formula when the decoupling cost is below a critical value. In the situation of high cost, we provide meaningful upper and lower bounds. This result is then applied to quantum state merging, exploiting its inherent connection to decoupling. In addition, as technical tools, we derive the exact exponents for the smoothing of the conditional min-entropy and max-information, and we prove a novel bound for the convex-split lemma. Our results are given in terms of the sandwiched Rényi divergence, providing it with a new type of operational meaning in characterizing how fast the performance of quantum information tasks approaches the perfect. This is a preview of subscription content, log in via an institution to check access. Access this article Price includes VAT (Russian Federation) Instant access to the full article PDF. 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Author information Authors and affiliations. Institute for Advanced Study in Mathematics, Harbin Institute of Technology, Harbin, 150001, China Ke Li & Yongsheng Yao School of Mathematics, Harbin Institute of Technology, Harbin, 150001, China Yongsheng Yao You can also search for this author in PubMed   Google Scholar Corresponding author Correspondence to Ke Li . Additional information Communicated by N. Linden. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Boundedness of the Upper Bound \(E_u(r)\) Proposition 21. Let \(\rho _{RA}\in \mathcal {S}(RA)\) be given. The function \(E_u(r)=\sup \limits _{s\ge 0}\big \{s\big (r-\frac{1}{2}I_{1+s}(R:A)_\rho \big )\big \}\) is bounded in the interval \((-\infty , \frac{1}{2}I_\textrm{max}(R:A)_\rho )\) . We show that there is a constant C , such that for any \(\epsilon >0\) , \(E_u\big (\frac{1}{2}I_\textrm{max}(R:A)_\rho -\epsilon \big )\le C\) . Proposition  16 establishes that where \(\omega ^{(n)}_{B^n}\) is the universal symmetric state of Lemma  1 and \(\mathcal {E}^n\) is the pinching map associated with \(\rho _A^{\otimes n}\otimes \omega ^{(n)}_{B^n}\) . Setting \(M_A=\rho _A\) and letting \(s\rightarrow \infty \) in Lemma  17 , we get This implies that, for arbitrary \(\epsilon >0\) , there exists a common eigenvector \(|\varphi _n\rangle \) of \(\mathcal {E}^n(\rho _{AB}^{\otimes n})\) and \(\rho _A^{\otimes n}\otimes \omega ^{(n)}_{B^n}\) , such that for n big enough, In Eq. ( A3 ), we have used the fact \(g_{n,|B|}\omega ^{(n)}_{B^n}\ge (\frac{\mathbbm {1}_B}{|B|})^{\otimes n}\) and \(\lambda _\textrm{min}(X)\) denotes the minimal eigenvalue of X . Combining Eq. ( A1 ), Eq. ( A2 ) and Eq. ( A3 ), we obtain At last, since \(E_u(r)\) is monotonically increasing, we can choose \(C=\frac{1}{2}\log \frac{|B|}{\lambda _\textrm{min}(\rho _A)} -\frac{1}{2}I_\textrm{max}(A:B)_\rho \) . \(\square \) Rights and permissions Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law. Reprints and permissions About this article Li, K., Yao, Y. Reliability Function of Quantum Information Decoupling via the Sandwiched Rényi Divergence. Commun. Math. Phys. 405 , 160 (2024). https://doi.org/10.1007/s00220-024-05029-z Download citation Received : 30 April 2022 Accepted : 06 May 2024 Published : 23 June 2024 DOI : https://doi.org/10.1007/s00220-024-05029-z Share this article Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative Find a journal Publish with us Track your research Elucidation of the Effect of Chain Dispersity on Microstructure and Mechanical Properties of Brush Particle Assembled Material  The field of nanocomposites emerged as a reconciliation of desirable features each from inorganic  particles (e.g., their capability for unique structural assemblies, conductivity, and quantum-scale  plasmonic character) and organic polymers (e.g., flexibility, toughness, processability, and  chemical versatility). Grafting of the polymer component to the surface of the inorganic  nanoparticle resulted in a new type of hybrid building block called brush particles, that enable  uniquely tunable homogeneous nanoparticle self-assemblies within a mechanically robust polymer  matrix. Nanocomposites often demand high inorganic loading, controllable and homogeneous  particle microstructure, and tunability of properties. To this end, several features of brush particle  material were explored. Molecular weight dispersity in the polymer canopy, inspired by long,  entanglement-forming chain toughening mechanisms, was shown to exhibit significantly higher  energy dissipation till failure through craze formation, at lower organic loadings than uniform  molecular weight distributions. This was accomplished with no detriment to the microstructural  uniformity. Additionally, isotropic microstructural trends were observed through multimodal  microstructure characterization (via electron microscopy and X-ray scattering), and spurred  examination of brush particles as a candidate for hyperuniform material formation. Finally,  machine learning regression tools were explored in an effort to establish predictive mapping from  the broad, tunable parameter space of brush architecture to desirable properties. The findings  presented in this work have made distinct strides in the effort to elucidate strengthening  mechanisms and microstructural character of brush particle materials as functions of the  architecture, and will spur further explorations into the fundamental phenomena governing these  interactions.  New Hybrid Materials by Controlled Polymerization of Monomers with Bulky Functional Substituents Directorate for Mathematical & Physical Sciences Bimodal Ligand Architectures for (Nano)particle Assembly Structures with Increased Strength and Fracture Resistance Directorate for Engineering Degree Type Dissertation Materials Science and Engineering Degree Name Doctor of Philosophy (PhD) Usage metrics Materials Engineering not elsewhere classified Help | Advanced Search Quantum Physics Title: cavity mode entanglement in relativistic quantum information. Abstract: A central aim of relativistic quantum information (RQI) is the investigation of quantum information tasks and resources taking into account the relativistic aspects of nature. More precisely, it is of fundamental interest to understand how the storage, manipulation, and transmission of information utilizing quantum systems are influenced by the fact that these processes take place in a relativistic spacetime. In particular, many studies in RQI have been focused on the effects of non-uniform motion on entanglement, the main resource of quantum information protocols. Early investigations in this direction were performed in highly idealized settings that prompted questions as to the practical accessibility of these results. To overcome these limitations it is necessary to consider quantum systems that are in principle accessible to localized observers. In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such as quantum teleportation. We study cavities in (1+1) dimensions undergoing non-uniform motion, consisting of segments of uniform acceleration and inertial motion of arbitrary duration that allow the involved velocities to become relativistic. The transitions between segments can be sharp or smooth and higher dimensions can be incorporated. The primary focus lies in the Bogoliubov transformations of the quantum fields, real scalar fields or Dirac fields, confined to the cavities. The Bogoliubov transformations change the particle content and the occupation of the energy levels of the cavity. We show how these effects generate entanglement between the modes of the quantum fields inside a single cavity for various initial states. The entanglement between several cavities, on the other hand, is degraded by the non-uniform motion, influencing the fidelity of tasks such as teleportation. Comments: PhD thesis, University of Nottingham, 2013, 200 pages, 34 figures, available from e-theses server at v2: updated references Subjects: Quantum Physics (quant-ph); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph) Cite as: [quant-ph]   (or [quant-ph] for this version)   Focus to learn more arXiv-issued DOI via DataCite Submission history Access paper:. Other Formats References & Citations INSPIRE HEP Google Scholar Semantic Scholar BibTeX formatted citation Bibliographic and Citation Tools Code, data and media associated with this article, recommenders and search tools. Institution arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs . 295 IMAGES (PDF) Quantum entanglement of particles in black hole neighborhoods IOPP: Title Detail: Fundamentals of Quantum Entanglement (Second 15 Best Quantum Entanglement Facts » HaimiWorld Quantum Entanglement PDF A Quantum Thesis Comes to Light Thesis Bjarnebouwer Hgqsat0x VIDEO Professor Brian Cox On Teleportation Four-Wave Mixing Theory for Cylindrical Vector Beams in Optical Fibre Mathematics of Quantum Entanglement, M. Christandl (University of Copenhagen), Part 2 Unraveling the Quantum World: The Story of Louis Victor de Broglie Quantum Entanglement 2024 UCalgary Three Minute Thesis Finalist: Anuj Sethia COMMENTS Graduate Thesis Or Dissertation Entangled states are a key resource in fundamental quantum physics, quantum cryptography, and quantum computation. In this thesis, we focus on the demonstrations of two novel methods to generate entanglement. First, we implement dissipative production of a maximally entangled steady state on two trapped ions. Entangling, Controlling, and Detecting Individual Strontium Atoms in We present a novel experimental platform for quantum and precision science: single strontium atoms trapped in arrays of optical tweezers. ... coherent control of the ultra-narrow clock transition; and inter-atom entanglement via Rydberg interactions. In the context of single-atom physics, we demonstrate trapping in tweezer arrays of one- and ... PDF Entanglement and Quantum Error Correction with Superconducting Qubits of particular interest because they redundantly encode quantum information. They are the basis of the quantum repetition code prototypical of more sophisticated schemes required for quantum computation. Using a three-qubit Toffoli gate, this code is demonstrated to autonomously correct either bit- or phase-flip errors. Despite observing the ... Spontaneous Parametric Down-Conversion and Quantum Entanglement Abstract. Quantum entanglement has been a topic of much research in modern physics, and an application in quantum computing is envisioned. This thesis address the use of polarization entangled photon pairs produced by spontaneous parametric down-conversion (SPDC) in entanglement transfer process and quantum computing. DataSpace: Quantum Order, Entanglement and Localization in Many-Body The next part of the thesis addresses the role of quantum entanglement, broadly speaking. Remarkably, it was shown that even highly-excited MBL eigenstates have low area-law entanglement. We exploit this feature to develop tensor-network based algorithms for efficiently computing and representing highly-excited MBL eigenstates. High-performance quantum entanglement generation via cascaded ... Quantum entanglement in different degrees of freedom is prepared and characterized with the setups shown in Fig. 2a-e. Figure 2a shows the experimental setup for generating correlated/entangled ... Coherent Control of Entanglement with Atomic Ensembles In this thesis, I describe a series of experiments whereby single excitations in atomic ensembles are strongly coupled to optical modes and provide efficient means for the coherent control of entangled states between matter and light. By following the seminal proposal by Duan et al., we have generated measurement-induced entanglement of an ... PhD thesis: Multipartite entanglement and quantum algorithms PhD thesis dealing with various aspects of multipartite entanglement, such as entanglement measures, absolutely maximally entangled states, bell inequalities, entanglement spectrum and quantum frustration. Also some quantum algorithms run with the IBM quantum computer are covered, together with others applied to adiabatic quantum computation and quantum thermodynamics. Entanglement between nodes of a quantum network Entanglement between nodes of a quantum network. Abstract: Quantum devices are rapidly gaining momentum as a technology that will induce a paradigm shift in computing, communication and cryptography. Trapped ion qubits are one of the leading candidates for implementing a quantum computer, having previously demonstrated all of the required criteria. Cavity mode entanglement in relativistic quantum information In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such as quantum teleportation. We study cavities in (1+1) dimensions undergoing non-uniform motion, consisting of segments of uniform acceleration and inertial motion of arbitrary duration ... PhD thesis: Multipartite entanglement and quantum algorithms PhD thesis dealing with various aspects of multipartite entanglement, such as entanglement measures, absolutely maximally entangled states, bell inequalities, entanglement spectrum and quantum ... PDF Experiments towards a Quantum Information Network with Squeezed Light A thesis submitted for the degree of Doctor of Philosophy The Australian National University October, 2003. To Eluca ... The entanglement is utilised in a quantum teleportation protocol, demonstrating that the quantum statistics of a eld can be transferred to another eld via detection and classical Symmetry, Topology and Entanglement in Quantum Many-Body Systems Symmetry, topology and entanglement are three indispensable concepts for our understanding of quantum many-body systems. In this dissertation, we demonstrate the use and interplay of these concepts with four distinct topics. The first part focuses on two-dimensional (2D) symmetry protected topological (SPT) phases with lattice rotation symmetries. PDF Entanglement in quantum communication Entanglement in quantum communication Preparation and characterization of photonic qubits DANIEL LJUNGGREN Doctoral Thesis Stockholm, Sweden 2006 PDF Spin squeezing and entanglement with room temperature atoms for quantum The work presented in this dissertation is a summary of research carried out between Sep 2011 and Jan 2015 as a PhD candidate in the Danish National Research Foundation Center for Quantum Optics (QUANTOP group) led by professor Eugene Polzik at the Niels Bohr Institute, University of Copenhagen. In the beginning of my PhD study, I had the pleasure PDF Quantum Information, Entanglement and Magnetometry With Macroscopic Gas gled states of light are stored in a quantum memory consisting of two separate atomic ensembles. The atomic system is also used as a sensor for magnetic fields. The magnetometer has a high sensitivity mainly limited by quantum projection noise. Entanglement-assisted magnetometry is demonstrated. Long-lived atomic entanglement is generated by ... Theses Quantum Simulations of the Ising Model: Devil's Staircase and Arbitrary Lattice Proposal, Simcha Korenblit, Ph.D. Physics (2013). Remote and Local Entanglement of Ions with Photons and Phonons, David Lee Hayes, Ph.D. Physics (2012). Quantum Simulation of Interacting Spin Models with Trapped Ions, Kazi Rajibul Islam, Ph.D. Physics (2012). [quant-ph/0610253] Entanglement in quantum information theory Entanglement in quantum information theory. This thesis covers several aspects of entanglement in the context of quantum information theory. 153 pages, 30 figures. An ancient PhD thesis, covering the time period April 1998 - December 2000. On quant-ph/9806088, quant-ph/9807034, quant-ph/9907021, quant-ph/9912080, quant-ph/0004076, quant-ph ... Quantum entanglement of the spatial modes of light This thesis is a dissemination of the experimental work I have carried out in the last three and a half years, under supervision of Prof. Miles Padgett and Dr. Sonja Franke-Arnold. Presented within are seven unique experiments investigating the orbital angular momentum (OAM) states of light, and the associated spatial modes. Six of these experiments relate to measurements on quantum-entangled ... Quantum measurement and entanglement of spin quantum bits in diamond Quantum measurement and entanglement of spin quantum bits in diamond. Pfaff, W. Applied Sciences. Quantum Nanoscience. 2013-12-20. This thesis presents a set of experiments that explore the possible realisation of a macroscopic quantum network based on solid-state quantum bits. Such a quantum network would allow for studying quantum mechanics ... Quantum measurement and entanglement of spin quantum bits in diamond This thesis presents a set of experiments in which quantum entanglement between non-interacting quantum bits — formed by single spins in diamond — is generated by quantum measurements, showing a way of prototyping quantum registers and networks (outlined in chapter 1.3). 1. 1. Introduction. Novel Quantum Devices and Innovative Simulation Methods for Quantum In this PhD dissertation a review of two novel quantum devices, which have been published previously, will be discussed. Additionally, extensions to the Finite Difference Method (FDM) which may be used in the study and design of future quantum systems more generally will also be explored. ... In this PhD dissertation a review of two novel ... Quantum entanglement just got a whole lot weirder (Credit: S. Freedman, PhD Thesis/LBNL, 1972) It's for this reason that quantum entanglement is often described as spooky and counterintuitive. However, quantum entanglement experiments usually ... Bruno De Souza Leao Torres PhD Thesis Defense Quantum Information Science and Technology ... Bruno De Souza Leao Torres PhD Thesis Defense. Thursday, July 4, 2024 10:30 am - 11:30 am EDT (GMT -04:00) ... Aspects of Quantum Information in Quantum Field Theory: Particle detector models, entanglement, and complexity. Supervisors: Dr. Eduardo Martin-Martinez, Dr. Beni Yoshida. Current students ... ARENBERG DOCTORAL SCHOOL Dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Science (PhD): Physics June 2024 Supervisor: Prof. dr. Thomas Van Riet arXiv:2406.19089v1 [hep-th] 27 Jun 2024 Reliability Function of Quantum Information Decoupling via the 3.1 Catalytic quantum information decoupling. Let a bipartite quantum state \(\rho _{RA}\in \mathcal {S}(RA)\) be given. Quantum information decoupling is the procedure of removing the information about system R from the A system, by performing a quantum operation on the A system. In catalytic quantum information decoupling, an auxiliary system \(A'\) in state that is independent of the state ... Elucidation of the Effect of Chain Dispersity on Microstructure and The field of nanocomposites emerged as a reconciliation of desirable features each from inorganic particles (e.g., their capability for unique structural assemblies, conductivity, and quantum-scale plasmonic character) and organic polymers (e.g., flexibility, toughness, processability, and chemical versatility). Grafting of the polymer component to the surface of the inorganic nanoparticle ... Cavity mode entanglement in relativistic quantum information In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such as quantum teleportation. We study cavities in (1+1) dimensions undergoing non-uniform motion, consisting of segments of uniform acceleration and inertial motion of arbitrary duration ... assignment essay homework paper phd report resume review speech