Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic...Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.展开更多
We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to sol...We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to solve the feedback-modified master equation, （ii） to demonstrate the ability of feedback control based on the solutions, and （iii） to pick out different steady states by choosing different driving strengths and feedback strengths to counteract the effects of both damping and the measurement back-action on the system. We further investigate some properties of the equilibrium steady state, its distribution probability and entanglement vs. the driving and feedback amplitudes. We find that in our feedback model feedback plays a negative role in producing entanglement.展开更多
Performing homodyne detection at a single output port of a squeezed-state light interferometer and then separating the measurement quadrature into two intervals can realize super-resolving and super-sensitive phase me...Performing homodyne detection at a single output port of a squeezed-state light interferometer and then separating the measurement quadrature into two intervals can realize super-resolving and super-sensitive phase measurements,which is equivalent to a binary-outcome measurement.Obviously,the single-port homodyne detection may lose almost part of the phase information,reducing the estimation precision.Here,we propose a data-processing technique over the doubleport homodyne detection,where the two-dimensional measurement quadrature(p1,p2)has been divided into two regions.With such a binary-outcome measurement,we estimate the phase shift accumulated in the interferometer by inverting the output signal.By analyzing the full width at half maximum of the signal and the phase sensitivity,we show that both the resolution and the achievable sensitivity are better than that of the previous binary-outcome scheme.展开更多
We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr n...We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr nonlinearity, and homodyne measurement, therefore it is feasible with current experimental technology, The success probability of our protocol is optimal, this property makes our protocol more efficient than others in the applications of quantum communication.展开更多
In this paper, we propose a deterministic quantum communication protocol using weak coherent states and pulsed homodyne detection. In this protocol, the communication parties exchange their secret information determin...In this paper, we propose a deterministic quantum communication protocol using weak coherent states and pulsed homodyne detection. In this protocol, the communication parties exchange their secret information deterministicaJly in two rounds. The devices and efficiency of the protocol are discussed respectively. We also show the security of the protocol against intercept-resend and Trojan-Horse eavesdropping attacks.展开更多
Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects...Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.展开更多
We theoretically investigate the phase sensitivity of a truncated SU(1,1)interferometer fed with a two-mode coherent state and employing double-port homodyne detection.On the one hand,we analytically demonstrate that ...We theoretically investigate the phase sensitivity of a truncated SU(1,1)interferometer fed with a two-mode coherent state and employing double-port homodyne detection.On the one hand,we analytically demonstrate that the two-mode coherent state provides better phase sensitivity than the single-mode coherent state.In addition,we show that the doubleport homodyne detection is a quasi-optimal measurement.For a bright coherent-state input,the sensitivity of this scheme saturates the phase-sensitivity bound determined by the quantum Fisher information.On the other hand,we quantitatively illustrate the advantage of double-port homodyne detection over the single-port scheme under ideal conditions and in the presence of photon loss,respectively.Furthermore,our analysis indicates that the scheme we propose is robust against photon loss.展开更多
Squeezed states belong to the most prominent non-classical resources.They have compelling applications in precise measurement, quantum computation, and detection.Here, we report on the direct measurement of 13.8 d B s...Squeezed states belong to the most prominent non-classical resources.They have compelling applications in precise measurement, quantum computation, and detection.Here, we report on the direct measurement of 13.8 d B squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection.By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%.The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor(JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector.展开更多
Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. ...Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.展开更多
We propose an optical tensor core(OTC) architecture for neural network training. The key computational components of the OTC are the arrayed optical dot-product units(DPUs). The homodyne-detection-based DPUs can condu...We propose an optical tensor core(OTC) architecture for neural network training. The key computational components of the OTC are the arrayed optical dot-product units(DPUs). The homodyne-detection-based DPUs can conduct the essential computational work of neural network training, i.e., matrix-matrix multiplication. Dual-layer waveguide topology is adopted to feed data into these DPUs with ultra-low insertion loss and cross talk. Therefore, the OTC architecture allows a large-scale dot-product array and can be integrated into a photonic chip. The feasibility of the OTC and its effectiveness on neural network training are verified with numerical simulations.展开更多
We experimentally study optical homodyne and heterodyne detections with the same setup, which is flexible to manipulate the signal sideband modulation. When the modulation only generates a single signal sideband, the ...We experimentally study optical homodyne and heterodyne detections with the same setup, which is flexible to manipulate the signal sideband modulation. When the modulation only generates a single signal sideband, the light field measurement by mixing the single sideband at ω0 ±? with a strong local oscillator at the carrier frequency ω0on a beam splitter becomes balanced heterodyne detection. When two signal sidebands at ω0 ±? are generated and the relative phase of the two sidebands is locked, this measurement corresponds to optical balanced homodyne detection. With this setup, we may confirm directly that the signal-to-noise ratio with heterodyne detection is two-fold worse than that with homodyne detection. This work will have important applications in quantum state measurement and quantum information.展开更多
Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance opt...Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance optical communication systems and in optical fiber WANs. There are two major patterns in coherent optical fiber communication: heterodyne and homodyne. Compared with the heterodyne scheme, the homodyne optical fiber communication system has the following advantages: (1) The sensitivity of the homodyne receiver is higher than that of the heterodyne receiver. As we know, the PSK homodyne optical fiber communication system has the highest sensitivity in coherent optical fiber communication systems. So it is much suitable to be used in long distance optical communication systems or in FDM systems. (2) Because the homodyne receiver only uses the baseband to demodulate the transmitted signals, it occupies much narrower frequency domain than the heterodyne receiver does, which makes it more suitable to be used in multichannel systems. (3) The demodulation pattern used in homodyne receiver is much easier than that used in the heterodyne receiver, since it only needs the baseband demodulation. Usually we construct a homodyne receiver with an optical phase locked loop (OPLL). The research of the OPLL began at 1960′s and the study of the homodyne receiver has been made gradually. In 1984, the first homodyne optical fiber communication system was demonstrated in BTRL, in which the signal laser and the local laser were all 1.5 μm He Ne gas lasers, and the OPLL used was a balanced one. In 1989, L.G.Kazovsky demonstrated experimentally a homodyne receiver in Bellcore using two 1.3 μm Nd:YAG lasers as the signal laser and the local laser and also using a balanced OPLL. Because the linewidth of the normal semiconductor laser is too large and its frequency stability is much poorer, it is very difficult to construct a homodyne receiver with the semiconductor lasers. At the end of 1989, the first Dissertation completed Jul. 1992homodyne optical fiber communication system using two 1.5 μm external cavity semiconductor lasers as the signal laser and the local laser, respectively, was finished in AT&T Bell Lab by J. M. Kahn, in which the OPLL was also a balanced one. In China, the research of the homodyne optical fiber communication system was funded by the National Seventh Five Year Program and by the National Natural Science Foundation. The difficulties to construct a homodyne optical fiber communication system are listed as follows: (1) In homodyne communication systems, the signal laser′s frequency should be stable to avoid the penalty of the receiver′s BER and the crosstalk to other channels in a FDM system, and the local laser could be tuned widely and easily to cover all the signal lasers′ frequency domain. Both the signal laser and the local laser should be narrow in linewidth to decrease the influence of the laser′s phase noise on the BER of the receiver. (2) The modulation pattern used should be studied and chosen carefully because the requirements of different kinds of modulation on the laser, the receiver and the channel are different. (3) Since the construction of the linear OPLL (the balanced) and the nonlinear OPLL (the Costas OPLL, or the Decision Driven OPLL) are rather different, their requirements on the linewidths of the lasers are different too, we should study the theory and the construction of the OPLL carefully to select the suitable scheme to realize. (4) In a multichannel system (such as a FDM system), the influence of crosstalk between channels on the homodyne system should be researched carefully. The technology used to stabilize the channel interval should also be studied. In this thesis, the homodyne optical fiber communication system has been theoretically analyzed, the technical difficulties of constructing the system have been studied. Several kinds of external cavity semiconductor laser have been researched experimentally. Compared展开更多
A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently ...A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photons, each causing a conditional phase rotation in the probe mode. Subsequent momentum quadrature homodyne measurement of the probe mode will project the photons in the signal mode into the desired entangled states. It is shown that under certain conditions, the four-photon cluster state can be generated with high fidelity and high success probability, and the scheme is feasible by current experimental technology.展开更多
We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in th...We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in three spatial separated cavities. Meanwhile, with the assistance of a coherent optical pulse and X-quadrature homodyne measurement, we can im- plement quantum dense coding with three-particle GHZ state with a higher probability. Our scheme can also be generalized to realize N-particle quantum dense coding.展开更多
We propose a possible approach to achieve a 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depen...We propose a possible approach to achieve a 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems may be lower than the quantum approaches and the sensitivity improvement is independent of frequency in all the detection bands.展开更多
We propose a scheme for generating a hyperentangled four-photon cluster state that is simultaneously entangled in polarization modes and spatial modes. This scheme is based on linear optical elements, weak cross-Kerr ...We propose a scheme for generating a hyperentangled four-photon cluster state that is simultaneously entangled in polarization modes and spatial modes. This scheme is based on linear optical elements, weak cross-Kerr nonlinearity, and homodyne detection. Therefore, it is feasible with current experimental technology.展开更多
Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local...Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.展开更多
We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically...We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one-and two-arm.Compared with the case of one-arm phase shift,the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough.Furthermore,we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula.In addition,we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1)interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses.展开更多
We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in ...We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in each Kerr medium, four-photon cluster state can be generated based on the results of two homodyne detectors in the first scheme. These schemes only use Kerr medium and homodyne measurements on coherent light fields, which can be effciently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.展开更多
We propose a scheme for long-distance quantum state transfer between different atoms based on cavity-assisted interactions. In our scheme, a coherent optical pulse sequentially interacts with two distant atoms trapped...We propose a scheme for long-distance quantum state transfer between different atoms based on cavity-assisted interactions. In our scheme, a coherent optical pulse sequentially interacts with two distant atoms trapped in separated cavities. Through the measurement of the state of the first atom and the homodyne detection of the final output coherent light, the quantum state can be transferred into the second atom with a success probability of unity and a fidelity of unity. In addition, our scheme neither requires the high-Q cavity working in the strong coupling regime nor employs the single-photon quantum channel, which greatly relaxes the experimental requirements.展开更多
基金supported by the Office of Naval Research(Grant Nos.N00014-16-1-2094 and N00014-24-1-2547)the Lawrence Livermore National Laboratory(Grant No.B622827)the National Science Foundation.Y.-S.J.acknowledges support from KRISS(Grant Nos.25011026 and 25011211).
文摘Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10775100,10974137 and 10805034the Fund of Theoretical Nuclear Center of HIRFL of Chinathe Scientific Research Foundation of CUIT under Grant No.KYTZ201024
文摘We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to solve the feedback-modified master equation, （ii） to demonstrate the ability of feedback control based on the solutions, and （iii） to pick out different steady states by choosing different driving strengths and feedback strengths to counteract the effects of both damping and the measurement back-action on the system. We further investigate some properties of the equilibrium steady state, its distribution probability and entanglement vs. the driving and feedback amplitudes. We find that in our feedback model feedback plays a negative role in producing entanglement.
基金the Science Foundation of Zhejiang Sci-Tech University,grant number 18062145-Ythe National Natural Science Foundation of China(NSFC)grant number12075209.
文摘Performing homodyne detection at a single output port of a squeezed-state light interferometer and then separating the measurement quadrature into two intervals can realize super-resolving and super-sensitive phase measurements,which is equivalent to a binary-outcome measurement.Obviously,the single-port homodyne detection may lose almost part of the phase information,reducing the estimation precision.Here,we propose a data-processing technique over the doubleport homodyne detection,where the two-dimensional measurement quadrature(p1,p2)has been divided into two regions.With such a binary-outcome measurement,we estimate the phase shift accumulated in the interferometer by inverting the output signal.By analyzing the full width at half maximum of the signal and the phase sensitivity,we show that both the resolution and the achievable sensitivity are better than that of the previous binary-outcome scheme.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61068001 and 11064016)
文摘We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr nonlinearity, and homodyne measurement, therefore it is feasible with current experimental technology, The success probability of our protocol is optimal, this property makes our protocol more efficient than others in the applications of quantum communication.
基金Supported by the National Fundamental Research Program under Grant No.2006CB921106National Natural Science Foundation of China under Grant Nos.10874098 and 10775076
文摘In this paper, we propose a deterministic quantum communication protocol using weak coherent states and pulsed homodyne detection. In this protocol, the communication parties exchange their secret information deterministicaJly in two rounds. The devices and efficiency of the protocol are discussed respectively. We also show the security of the protocol against intercept-resend and Trojan-Horse eavesdropping attacks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62331024 and 62571549)the National Key Research and Development Program of China(Grant No.2022YFB2802804)。
文摘Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12104193 and U24A2017)National Undergraduate Training Program for Innovation and Entrepreneurship(Grant No.202411463037Z)the project of Changzhou Physics Society Fund(Grant No.CW20250102)。
文摘We theoretically investigate the phase sensitivity of a truncated SU(1,1)interferometer fed with a two-mode coherent state and employing double-port homodyne detection.On the one hand,we analytically demonstrate that the two-mode coherent state provides better phase sensitivity than the single-mode coherent state.In addition,we show that the doubleport homodyne detection is a quasi-optimal measurement.For a bright coherent-state input,the sensitivity of this scheme saturates the phase-sensitivity bound determined by the quantum Fisher information.On the other hand,we quantitatively illustrate the advantage of double-port homodyne detection over the single-port scheme under ideal conditions and in the presence of photon loss,respectively.Furthermore,our analysis indicates that the scheme we propose is robust against photon loss.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.11654002,61575114,11874250,and 11804207)National Key Research and Development Program of China(No.2016YFA0301401)+2 种基金Program for Sanjin Scholar of Shanxi ProvinceProgram for Outstanding Innovative Teams of Higher Learning Institutions of ShanxiFund for Shanxi “1331 Project”Key Subjects Construction
文摘Squeezed states belong to the most prominent non-classical resources.They have compelling applications in precise measurement, quantum computation, and detection.Here, we report on the direct measurement of 13.8 d B squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection.By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%.The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor(JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector.
基金supported by the National Natural Science Foundation of China (60372061)Basic Fund for the Scientific Research Project of Jilin University (200903296)
文摘Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.
基金supported by the National Key R&D Program of China (No.2019YFB2203700)the National Natural Science Foundation of China (No.61822508)。
文摘We propose an optical tensor core(OTC) architecture for neural network training. The key computational components of the OTC are the arrayed optical dot-product units(DPUs). The homodyne-detection-based DPUs can conduct the essential computational work of neural network training, i.e., matrix-matrix multiplication. Dual-layer waveguide topology is adopted to feed data into these DPUs with ultra-low insertion loss and cross talk. Therefore, the OTC architecture allows a large-scale dot-product array and can be integrated into a photonic chip. The feasibility of the OTC and its effectiveness on neural network training are verified with numerical simulations.
基金supported by the National Basic Research Program of China(Grant No.2011CB921601)the National Natural Science Foundation of China(Grant Nos.10725416 and 60821004)
文摘We experimentally study optical homodyne and heterodyne detections with the same setup, which is flexible to manipulate the signal sideband modulation. When the modulation only generates a single signal sideband, the light field measurement by mixing the single sideband at ω0 ±? with a strong local oscillator at the carrier frequency ω0on a beam splitter becomes balanced heterodyne detection. When two signal sidebands at ω0 ±? are generated and the relative phase of the two sidebands is locked, this measurement corresponds to optical balanced homodyne detection. With this setup, we may confirm directly that the signal-to-noise ratio with heterodyne detection is two-fold worse than that with homodyne detection. This work will have important applications in quantum state measurement and quantum information.
文摘Because it has the advantages of high sensitivity, and it is easy to demodulate and convenient to select in FDM system, the coherent optical fiber communication system is much suitable to be used in long distance optical communication systems and in optical fiber WANs. There are two major patterns in coherent optical fiber communication: heterodyne and homodyne. Compared with the heterodyne scheme, the homodyne optical fiber communication system has the following advantages: (1) The sensitivity of the homodyne receiver is higher than that of the heterodyne receiver. As we know, the PSK homodyne optical fiber communication system has the highest sensitivity in coherent optical fiber communication systems. So it is much suitable to be used in long distance optical communication systems or in FDM systems. (2) Because the homodyne receiver only uses the baseband to demodulate the transmitted signals, it occupies much narrower frequency domain than the heterodyne receiver does, which makes it more suitable to be used in multichannel systems. (3) The demodulation pattern used in homodyne receiver is much easier than that used in the heterodyne receiver, since it only needs the baseband demodulation. Usually we construct a homodyne receiver with an optical phase locked loop (OPLL). The research of the OPLL began at 1960′s and the study of the homodyne receiver has been made gradually. In 1984, the first homodyne optical fiber communication system was demonstrated in BTRL, in which the signal laser and the local laser were all 1.5 μm He Ne gas lasers, and the OPLL used was a balanced one. In 1989, L.G.Kazovsky demonstrated experimentally a homodyne receiver in Bellcore using two 1.3 μm Nd:YAG lasers as the signal laser and the local laser and also using a balanced OPLL. Because the linewidth of the normal semiconductor laser is too large and its frequency stability is much poorer, it is very difficult to construct a homodyne receiver with the semiconductor lasers. At the end of 1989, the first Dissertation completed Jul. 1992homodyne optical fiber communication system using two 1.5 μm external cavity semiconductor lasers as the signal laser and the local laser, respectively, was finished in AT&T Bell Lab by J. M. Kahn, in which the OPLL was also a balanced one. In China, the research of the homodyne optical fiber communication system was funded by the National Seventh Five Year Program and by the National Natural Science Foundation. The difficulties to construct a homodyne optical fiber communication system are listed as follows: (1) In homodyne communication systems, the signal laser′s frequency should be stable to avoid the penalty of the receiver′s BER and the crosstalk to other channels in a FDM system, and the local laser could be tuned widely and easily to cover all the signal lasers′ frequency domain. Both the signal laser and the local laser should be narrow in linewidth to decrease the influence of the laser′s phase noise on the BER of the receiver. (2) The modulation pattern used should be studied and chosen carefully because the requirements of different kinds of modulation on the laser, the receiver and the channel are different. (3) Since the construction of the linear OPLL (the balanced) and the nonlinear OPLL (the Costas OPLL, or the Decision Driven OPLL) are rather different, their requirements on the linewidths of the lasers are different too, we should study the theory and the construction of the OPLL carefully to select the suitable scheme to realize. (4) In a multichannel system (such as a FDM system), the influence of crosstalk between channels on the homodyne system should be researched carefully. The technology used to stabilize the channel interval should also be studied. In this thesis, the homodyne optical fiber communication system has been theoretically analyzed, the technical difficulties of constructing the system have been studied. Several kinds of external cavity semiconductor laser have been researched experimentally. Compared
基金supported by the National Natural Science Foundation of China (Grant No. 11074002)the Doctoral Foundation of the Ministry of Education of China (Grant No. 20103401110003)the Personal Development Foundation of Anhui Province (Grant No. 2008Z018)
文摘A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photons, each causing a conditional phase rotation in the probe mode. Subsequent momentum quadrature homodyne measurement of the probe mode will project the photons in the signal mode into the desired entangled states. It is shown that under certain conditions, the four-photon cluster state can be generated with high fidelity and high success probability, and the scheme is feasible by current experimental technology.
基金supported by the National Natural Science Foundation of China(Grant Nos.11074002 and 61275119)the Doctoral Foundation of the Ministry of Education of China(Grant No.20103401110003)the Natural Science Research Project of Education Department of Anhui Province,China(Grant Nos.KJ2013A205,KJ2011ZD07,and KJ2012Z309)
文摘We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in three spatial separated cavities. Meanwhile, with the assistance of a coherent optical pulse and X-quadrature homodyne measurement, we can im- plement quantum dense coding with three-particle GHZ state with a higher probability. Our scheme can also be generalized to realize N-particle quantum dense coding.
基金Supported by the National Natural Science Foundation of China under Grant No 60407003.
文摘We propose a possible approach to achieve a 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems may be lower than the quantum approaches and the sensitivity improvement is independent of frequency in all the detection bands.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(Grant No.91121023)the National Natural Science Foundation of China(Grant Nos.60978009 and 61378012)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20124407110009)the"973"Project(Grant Nos.2011CBA00200 and 2013CB921804)the PCSIRT(Grant No.IRT1243)
文摘We propose a scheme for generating a hyperentangled four-photon cluster state that is simultaneously entangled in polarization modes and spatial modes. This scheme is based on linear optical elements, weak cross-Kerr nonlinearity, and homodyne detection. Therefore, it is feasible with current experimental technology.
基金Project supported by the National Special Fund for Major Research Instrument Development of China(Grant No.11527808)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11504262)+2 种基金the National Basic Research Program of China(Grant No.2014CB340103)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120032110055)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.14JCQNJC02300)
文摘Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11747161 and 11974189the China Postdoctoral Science Foundation under Grant No.2018M642293
文摘We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one-and two-arm.Compared with the case of one-arm phase shift,the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough.Furthermore,we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula.In addition,we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1)interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses.
基金National Natural Science Foundation of China under Grant No.10574022the Natural Science Foundation of Fujian Province of China under Grant Nos.2007J0002 and 2007J0197the Foundation for Universities in Fujian Province under Grant No.2007F5041
文摘We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in each Kerr medium, four-photon cluster state can be generated based on the results of two homodyne detectors in the first scheme. These schemes only use Kerr medium and homodyne measurements on coherent light fields, which can be effciently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.
基金supported by the National Natural Science Foundation of China(Grant No.60978009)the National Basic Research Program of China(Grant Nos.2009CB929604 and 2007CB925204)
文摘We propose a scheme for long-distance quantum state transfer between different atoms based on cavity-assisted interactions. In our scheme, a coherent optical pulse sequentially interacts with two distant atoms trapped in separated cavities. Through the measurement of the state of the first atom and the homodyne detection of the final output coherent light, the quantum state can be transferred into the second atom with a success probability of unity and a fidelity of unity. In addition, our scheme neither requires the high-Q cavity working in the strong coupling regime nor employs the single-photon quantum channel, which greatly relaxes the experimental requirements.
