The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compa...The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.展开更多
Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However...Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.展开更多
In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the p...In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the position information of the target,which will lose energy.In this paper,a long time integration method of radar signal based on rotating target radon Fourier transform(RTRFT)is proposed.This method modifies the distance and frequency terms in the traditional generalized radon Fourier transform(GRFT),and adds the frequency sinusoidal modulation term.Then,based on the cardinality balanced multi-target multi-Bernoulli(CBMeMBer)filter,the position of the target is detected in the high-dimensional space obtained by RTRFT.This method can combine coherent integration and micro-motion parameter estimation.Simulation experiments show that the proposed method can estimate the main translational parameters and rotational micro-motion parameters of the target while detecting the target,and the target detection performance is improved.展开更多
This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation ...This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation comparison with conventional frequency-domain adaptation schemes. It was found that the cluster size plays an important role on the adaptation performance, especially for the vehicular environment. Simulation results showed that using Lagrange interpolation to obtain an explicit curve of Doppler frequency vs cluster size yields good trade-off between the resulted bit error rate (BER) and the amount of feedback.展开更多
Compared with full device-independent quantum key distribution（DI-QKD）, one-side device-independent QKD（1s DI-QKD） needs fewer requirements, which is much easier to meet. In this paper, by applying recently develo...Compared with full device-independent quantum key distribution（DI-QKD）, one-side device-independent QKD（1s DI-QKD） needs fewer requirements, which is much easier to meet. In this paper, by applying recently developed novel time–energy entropic uncertainty relations, we present a time–energy high-dimensional one-side device-independent quantum key distribution（HD-QKD） and provide the security proof against coherent attacks. Besides, we connect the security with the quantum steering. By numerical simulation, we obtain the secret key rate for Alice＇s different detection efficiencies. The results show that our protocol can performance much better than the original 1s DI-QKD. Furthermore, we clarify the relation among the secret key rate, Alice＇s detection efficiency, and the dispersion coefficient. Finally, we simply analyze its performance in the optical fiber channel.展开更多
Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback co...Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.展开更多
The optical Ramsey spectrum is experimentally realized in an ^(87)Sr optical lattice clock, and the measured linewidth agrees well with theoretical expectation. The coherence time between the clock laser and the atoms...The optical Ramsey spectrum is experimentally realized in an ^(87)Sr optical lattice clock, and the measured linewidth agrees well with theoretical expectation. The coherence time between the clock laser and the atoms, which indicates the maximum free evolution period of using Ramsey detection to measure the atom-laser phase information, is determined as 340(23) ms by measuring the fringe contrasts of the Ramsey spectrum as a function of the free evolution period. Furthermore, with the same clock duty cycle of about 0.1, the clock stability is measured by using the Ramsey and Rabi spectra,respectively. The experimental and theoretical results show approximately the same stability as the two detection methods, which indicates that Ramsey detection cannot obviously improve the clock stability until the clock duty cycle is large enough. Thus, it is of great significance to choose the detection method of a specific clock.展开更多
A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation(CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. The trai...A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation(CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. The training symbol of the proposed algorithm is comprised of four different parts, utilizing even symmetry property of each part to accomplish timing synchronization. The performance of the proposed algorithm is demonstrated by means of simulations in OFDM and CO-OFDM systems. The proposed algorithm is shown to eliminate the timing sidelobes of Park's algorithm and has a more accurate timing estimation. In the condition of chromatic dispersion(CD), the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost 0 at all the other positions. Meanwhile, the timing mean square error(MSE) of the proposed algorithm remains around 10^(-6).展开更多
The nitrogen-vacancy(NV)center in diamond is a point defect formed by a substitutional nitrogen atom adjacent to a carbon vacancy.Owing to its exceptional fluorescence properties and long quantum coherence,the NV cent...The nitrogen-vacancy(NV)center in diamond is a point defect formed by a substitutional nitrogen atom adjacent to a carbon vacancy.Owing to its exceptional fluorescence properties and long quantum coherence,the NV center has broad applications in quantum computing,quantum sensing,and magnetic field imaging.This study focuses on the magnetic field sensing capabilities of NV centers,with performance critically dependent on the NV concentrations and coherence time.High-performance NV center diamond samples were synthesized using microwave plasma chemical vapor deposition(MPCVD)with controlled nitrogen doping,followed by electron irradiation and high-temperature annealing.We obtained diamond samples with high NV concentrations and a coherence time of T_(2)*=0.48µs.These diamonds were processed into micrometer-sized crystals via laser cutting and polishing,then integrated into an optical fiber-based probe for magnetic field detection.The sensor’s performance was first characterized independently,with a magnetic sensitivity of 5.77nT/√Hz and a magnetic resolution of 0.1 G@4715 G.Subsequently,two-dimensional magnetic field imaging experiments were performed on chip surfaces,demonstrating the probe’s capability for precise mapping of local magnetic fields.展开更多
Raman scattering spectroscopy is widely used as an analytical technique in various fields,but its measurement process tends to be slow due to the low scattering cross-section.In the last decade,various broadband coher...Raman scattering spectroscopy is widely used as an analytical technique in various fields,but its measurement process tends to be slow due to the low scattering cross-section.In the last decade,various broadband coherent Raman scattering spectroscopy techniques have been developed to address this limitation,achieving a measurement rate of 500 kSpectra/s.Here,we present a substantially increased measurement rate of 50 MSpectra/s,which is 100 times higher than the previous state-of-the-art,by developing time-stretch coherent Raman scattering spectroscopy.Our newly developed system,based on a mode-locked Yb fiber laser,enables highly efficient broadband excitation of molecular vibrations via impulsive stimulated Raman scattering with an ultrashort femtosecond pulse and sensitive time-stretch detection with a picosecond probe pulse at a high repetition rate of the laser.As a proof-of-concept demonstration,we measure broadband coherent Stokes Raman scattering spectra of organic compounds covering the molecular fingerprint region from 200 to 1,200 cm^(-1).This high-speed broadband vibrational spectroscopy technique holds promise for unprecedented measurements of sub-microsecond dynamics of irreversible phenomena and extremely high-throughput measurements.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2021YFA1402002)the Innovation Program for Quantum Science and Technology (Grant No.2023ZD0300400)the National Natural Science Foundation of China (Grant Nos.U21A6006,U21A20433,92465201,12474360,and 92265108)。
文摘The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.
基金supported by the National Natural Science Foundation of China(Grant Nos.112374012 and 11974208)Shandong Provincial Natural Science Foundation(Grant Nos.ZR2023JQ001 and tsqn202211128)。
文摘Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.
文摘In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the position information of the target,which will lose energy.In this paper,a long time integration method of radar signal based on rotating target radon Fourier transform(RTRFT)is proposed.This method modifies the distance and frequency terms in the traditional generalized radon Fourier transform(GRFT),and adds the frequency sinusoidal modulation term.Then,based on the cardinality balanced multi-target multi-Bernoulli(CBMeMBer)filter,the position of the target is detected in the high-dimensional space obtained by RTRFT.This method can combine coherent integration and micro-motion parameter estimation.Simulation experiments show that the proposed method can estimate the main translational parameters and rotational micro-motion parameters of the target while detecting the target,and the target detection performance is improved.
基金Project supported by the Hi-Tech Research and Development Pro-gram (863) of China (No. 2003AA123310), and the National Natural Science Foundation of China (No. 60332030)
文摘This paper proposes a time-domain clustered transmitter power adaptation scheme for orthogonal frequency division multiplexing (OFDM) system, which can significantly reduce the feedback amount during power adaptation comparison with conventional frequency-domain adaptation schemes. It was found that the cluster size plays an important role on the adaptation performance, especially for the vehicular environment. Simulation results showed that using Lagrange interpolation to obtain an explicit curve of Doppler frequency vs cluster size yields good trade-off between the resulted bit error rate (BER) and the amount of feedback.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB338002)the National Natural Science Foundation of China(Grants Nos.11304397 and 61505261)
文摘Compared with full device-independent quantum key distribution（DI-QKD）, one-side device-independent QKD（1s DI-QKD） needs fewer requirements, which is much easier to meet. In this paper, by applying recently developed novel time–energy entropic uncertainty relations, we present a time–energy high-dimensional one-side device-independent quantum key distribution（HD-QKD） and provide the security proof against coherent attacks. Besides, we connect the security with the quantum steering. By numerical simulation, we obtain the secret key rate for Alice＇s different detection efficiencies. The results show that our protocol can performance much better than the original 1s DI-QKD. Furthermore, we clarify the relation among the secret key rate, Alice＇s detection efficiency, and the dispersion coefficient. Finally, we simply analyze its performance in the optical fiber channel.
基金supported by the National Natural Science Foundation of China(Grant No.U2230207)。
文摘Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61775220)the Key Research Project of Frontier Science of the Chinese Academy of Sciences (Grant No. QYZDB-SSW-JSC004)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB21030100)。
文摘The optical Ramsey spectrum is experimentally realized in an ^(87)Sr optical lattice clock, and the measured linewidth agrees well with theoretical expectation. The coherence time between the clock laser and the atoms, which indicates the maximum free evolution period of using Ramsey detection to measure the atom-laser phase information, is determined as 340(23) ms by measuring the fringe contrasts of the Ramsey spectrum as a function of the free evolution period. Furthermore, with the same clock duty cycle of about 0.1, the clock stability is measured by using the Ramsey and Rabi spectra,respectively. The experimental and theoretical results show approximately the same stability as the two detection methods, which indicates that Ramsey detection cannot obviously improve the clock stability until the clock duty cycle is large enough. Thus, it is of great significance to choose the detection method of a specific clock.
文摘A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation(CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing(CO-OFDM) systems. The training symbol of the proposed algorithm is comprised of four different parts, utilizing even symmetry property of each part to accomplish timing synchronization. The performance of the proposed algorithm is demonstrated by means of simulations in OFDM and CO-OFDM systems. The proposed algorithm is shown to eliminate the timing sidelobes of Park's algorithm and has a more accurate timing estimation. In the condition of chromatic dispersion(CD), the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost 0 at all the other positions. Meanwhile, the timing mean square error(MSE) of the proposed algorithm remains around 10^(-6).
基金financial support by the National Key Research and Development Program of China (Grant No. 2021YFB2012600)the Fund of National Key laboratory of Plasma Physics (Grant No. 6142A04240204)+5 种基金the National Natural Science Foundation of China (Grant No. 62474165)the Science and Technology Major Project of Henan Province (Grant No. 231100230300)the Henan Association for Science and Technology Youth Talent Support Program (Grant No. 2024HYTP024)the Key Research and Development Project of Henan Province (Grant No. 231111232100)the Natural Science Foundation of Henan Province (Grant No. 252300421228)Zhongyuan Science and Technology Innovation Youth Top Talent Program
文摘The nitrogen-vacancy(NV)center in diamond is a point defect formed by a substitutional nitrogen atom adjacent to a carbon vacancy.Owing to its exceptional fluorescence properties and long quantum coherence,the NV center has broad applications in quantum computing,quantum sensing,and magnetic field imaging.This study focuses on the magnetic field sensing capabilities of NV centers,with performance critically dependent on the NV concentrations and coherence time.High-performance NV center diamond samples were synthesized using microwave plasma chemical vapor deposition(MPCVD)with controlled nitrogen doping,followed by electron irradiation and high-temperature annealing.We obtained diamond samples with high NV concentrations and a coherence time of T_(2)*=0.48µs.These diamonds were processed into micrometer-sized crystals via laser cutting and polishing,then integrated into an optical fiber-based probe for magnetic field detection.The sensor’s performance was first characterized independently,with a magnetic sensitivity of 5.77nT/√Hz and a magnetic resolution of 0.1 G@4715 G.Subsequently,two-dimensional magnetic field imaging experiments were performed on chip surfaces,demonstrating the probe’s capability for precise mapping of local magnetic fields.
基金supported by JSPS KAKENHI(20H00125,21K20500,and 23H00273),Research Foundation for Opto-Science and Technology,Nakatani FoundationUTEC-UTokyo FSI Research Grant Program.
文摘Raman scattering spectroscopy is widely used as an analytical technique in various fields,but its measurement process tends to be slow due to the low scattering cross-section.In the last decade,various broadband coherent Raman scattering spectroscopy techniques have been developed to address this limitation,achieving a measurement rate of 500 kSpectra/s.Here,we present a substantially increased measurement rate of 50 MSpectra/s,which is 100 times higher than the previous state-of-the-art,by developing time-stretch coherent Raman scattering spectroscopy.Our newly developed system,based on a mode-locked Yb fiber laser,enables highly efficient broadband excitation of molecular vibrations via impulsive stimulated Raman scattering with an ultrashort femtosecond pulse and sensitive time-stretch detection with a picosecond probe pulse at a high repetition rate of the laser.As a proof-of-concept demonstration,we measure broadband coherent Stokes Raman scattering spectra of organic compounds covering the molecular fingerprint region from 200 to 1,200 cm^(-1).This high-speed broadband vibrational spectroscopy technique holds promise for unprecedented measurements of sub-microsecond dynamics of irreversible phenomena and extremely high-throughput measurements.
