Due to the potential of quantum advantage to surpass the standard quantum limit(SQL),nonlinear interferometers have garnered significant attention from researchers in the field of precision measurement.However,many pr...Due to the potential of quantum advantage to surpass the standard quantum limit(SQL),nonlinear interferometers have garnered significant attention from researchers in the field of precision measurement.However,many practical applications require multiparameter estimation.In this work,we discuss the precision limit of multi-parameter estimation of pure Gaussian states based on nonlinear interferometers,and derive the Holevo Cramér–Rao bound(HCRB)for the case where both modes undergo displacement estimation.Furthermore,we compare our analytical results with the quantum Cramér–Rao bound based on the symmetric logarithmic derivative(SLD-CRB),and with the result of the dual homodyne measurement.Through numerical analysis,we find that the HCRB equals the result of the dual homodyne measurement,whereas SLD-CRB is not saturable at small squeezed parameters.Therefore,this indicates that the HCRB is tight.Additionally,we provide intuitive analysis and visual representation of our numerical results in phase space.展开更多
We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses.The uneven nonlinea...We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses.The uneven nonlinear interferometer,providing a more ideal interference pattern due to the elimination of secondary maxima,consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers,and the lengths of the nonlinear fibers follow the binomial distribution.The mode number of the photon pairs deduced from the measured joint spectrum is∼1.03.The collection efficiency of the photon pairs is found to be∼94%(after background noise correction).The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is∼92%,while no interference is observed in the direct detection of either the signal or idler photons.展开更多
A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s outp...A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s output signals.展开更多
Nonlinear materials have been well established as photo refractive switching material. Important applica- tions of isotropic nonlinear materials are seen in self-focusing, defocusing phenomena, switching systems, etc....Nonlinear materials have been well established as photo refractive switching material. Important applica- tions of isotropic nonlinear materials are seen in self-focusing, defocusing phenomena, switching systems, etc. The nonlinear correction term is basically responsible for the optical switches. Mach-Zehnder inter- ferometer （MZI） is a well-known arrangement for determining the above correction term, but there are some major problems for finding out the term by MZI. We propose a new method of finding the nonlinear correction term as well as the second order nonlinear susceptibility of the materials by using a modified MZI system. This method may be used to find out the above parameters for any unknown nonlinear material.展开更多
Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bos...Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bose−Einstein condensate trapped in an optical cavity. We unravel that the phase sensitivity can be greatly enhanced with the cavity-mediated nonlinear interaction. The influence of encoding phase, splitting time and recombining time on phase sensitivity are carefully studied. In addition, we demonstrate a dynamical phase transition in the system. Around the criticality, a small cavity light field variation can arouse a strong response of the atomic condensate, which can serve as a new resource for enhanced sensing. This work provides a robust protocol for cavity-enhanced metrology.展开更多
基金supported by the Shanghai Science and Technology Innovation Project(No.24LZ1400600)the Innovation Program for Quantum Science and Technology(No.2021ZD0303200)+4 种基金the National Natural Science Foundation of China(Grant Nos.U23A2075,12274132,11974111,12234014,11654005,11874152,and 91536114)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Innovation Program of Shanghai Municipal Education Commission(No.202101070008E00099)the National Key Research and Development Program of China(Grant No.2016YFA0302001)Fundamental Research Funds for the Central Universities.
文摘Due to the potential of quantum advantage to surpass the standard quantum limit(SQL),nonlinear interferometers have garnered significant attention from researchers in the field of precision measurement.However,many practical applications require multiparameter estimation.In this work,we discuss the precision limit of multi-parameter estimation of pure Gaussian states based on nonlinear interferometers,and derive the Holevo Cramér–Rao bound(HCRB)for the case where both modes undergo displacement estimation.Furthermore,we compare our analytical results with the quantum Cramér–Rao bound based on the symmetric logarithmic derivative(SLD-CRB),and with the result of the dual homodyne measurement.Through numerical analysis,we find that the HCRB equals the result of the dual homodyne measurement,whereas SLD-CRB is not saturable at small squeezed parameters.Therefore,this indicates that the HCRB is tight.Additionally,we provide intuitive analysis and visual representation of our numerical results in phase space.
基金supported by the National Natural Science Foundation of China (Nos.12074283,91836302,11874279,and 62305240)
文摘We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses.The uneven nonlinear interferometer,providing a more ideal interference pattern due to the elimination of secondary maxima,consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers,and the lengths of the nonlinear fibers follow the binomial distribution.The mode number of the photon pairs deduced from the measured joint spectrum is∼1.03.The collection efficiency of the photon pairs is found to be∼94%(after background noise correction).The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is∼92%,while no interference is observed in the direct detection of either the signal or idler photons.
文摘A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s output signals.
文摘Nonlinear materials have been well established as photo refractive switching material. Important applica- tions of isotropic nonlinear materials are seen in self-focusing, defocusing phenomena, switching systems, etc. The nonlinear correction term is basically responsible for the optical switches. Mach-Zehnder inter- ferometer （MZI） is a well-known arrangement for determining the above correction term, but there are some major problems for finding out the term by MZI. We propose a new method of finding the nonlinear correction term as well as the second order nonlinear susceptibility of the materials by using a modified MZI system. This method may be used to find out the above parameters for any unknown nonlinear material.
文摘Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bose−Einstein condensate trapped in an optical cavity. We unravel that the phase sensitivity can be greatly enhanced with the cavity-mediated nonlinear interaction. The influence of encoding phase, splitting time and recombining time on phase sensitivity are carefully studied. In addition, we demonstrate a dynamical phase transition in the system. Around the criticality, a small cavity light field variation can arouse a strong response of the atomic condensate, which can serve as a new resource for enhanced sensing. This work provides a robust protocol for cavity-enhanced metrology.
