In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed...In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.展开更多
We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In ...We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In our proposal,we use a dissipative TLS ensemble and an active cavity with effective gain.In the weak drive-field limit,the QPT can occur under the combined actions of the loss and gain of the system.Owing to the active cavity,the QPT behavior can be much differentiated even for a finite strength of the drive field on the TLS ensemble.Also,we propose to implement our scheme based on the dissipative nitrogen-vacancy(NV)centers coupled to an active optical cavity made from the gainmedium-doped silica.Furthermore,we show that the QPT can be measured by probing the transmission spectrum of the cavity embedding the ensemble of the NV centers.展开更多
When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show ...When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show the nonlinearity and heating-induced frequency shifts of the Kittel mode and HMS mode in a yttrium-iron-garnet(YIG)sphere.When the Kittel mode is driven to generate a certain number of excitations,the temperature of the whole YIG sample rises and the HMS mode can display an induced frequency shift,and vice versa.This cross effect provides a new method to study the magnetization dynamics and paves a way for novel cavity magnonic devices by including the heating effect as an operational degree of freedom.展开更多
Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the 3d ^2D3/2-3d ^2D5/2 transition in the potassium-like （K-like） sequence with 26 ≤ Z ≤ 36 are investigated by using the m...Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the 3d ^2D3/2-3d ^2D5/2 transition in the potassium-like （K-like） sequence with 26 ≤ Z ≤ 36 are investigated by using the multi-configuration Dirac-Hartree-Fock （MCDHF） method. The contributions of the electron correlations, Breit interaction, and the leading-order quantum electrodynamic （QED） effects on the transition properties are analyzed. The present results are interested in the laboratory tokamak and the astronomical observations. Furthermore, the feasibility of these ions for the highly charged ion （HCI） clocks is discussed. Considering the wavelength of lasers and manipulation process of the atomic clocks, Cu^10＋ and Zn^11＋ are recommended as promising candidates with achievable quality factors at the 10^15 level.展开更多
Accurate isotope shift factors of the 2s2p^（3,1）P_1~o–2s^2 ~1S_0 transitions in B II, obtained with the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods, are reported....Accurate isotope shift factors of the 2s2p^（3,1）P_1~o–2s^2 ~1S_0 transitions in B II, obtained with the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods, are reported. We found a linear correlation relation between the mass shift factors and the energies for the transitions concerned, considering all-order electron correlations. This relation is important for estimating the uncertainty in the calculation of isotope shift factors. These atomic data can be used to extract the nuclear mean-square charge radii of the boron isotopes with halo structures or to resolve the high precise spectroscopy of B II in astronomical observation.展开更多
Ghost imaging has been attracting more and more attention, which provides a way to obtain images of objects with only a single-pixel detector. Considering possible applications, it becomes urgent to clarify the sensit...Ghost imaging has been attracting more and more attention, which provides a way to obtain images of objects with only a single-pixel detector. Considering possible applications, it becomes urgent to clarify the sensitivity of ghost imaging. Due to the unique characteristics of single-pixel detectors, which collect photons without distributing them to multiple pixels,often outperforming array sensors, ghost imaging is believed to be more sensitive than conventional imaging. However,a systematic analysis on the sensitivity of ghost imaging is yet to be completed. In this paper, we present a method for quantitatively assessing the sensitivity of ghost imaging. A detailed comparison is provided between ghost imaging and conventional imaging, taking into account the particle nature of photons and the noise of detection. With the settings of the two imaging methods being the same to the most extent, the minimal required number of detected photons for images of a certain quality is considered. For the thermal source version, ghost imaging demonstrates enhanced sensitivity under practical situations, with noise considered.Employing an entangled source, ghost imaging surpasses conventional imaging techniques in terms of sensitivity obviously. In one word, ghost imaging promises higher sensitivity at low photon flux and noisy situations.展开更多
Study on optical correlation function initiates the development of many quantum techniques, with ghost imaging(GI) being one of the great achievements. Upon the first demonstration with entangled sources, the physics ...Study on optical correlation function initiates the development of many quantum techniques, with ghost imaging(GI) being one of the great achievements. Upon the first demonstration with entangled sources, the physics and improvements of GI attracted much interest. Among existing studies, GI with classical sources provoked debates and ideas to the most extent.Toward better understanding and practical applications of GI, fundamental theory, various designs of illumination patterns as well as reconstruction algorithms, demonstrations and field tests have been reported, with the topic of GI very much enriched. In this paper, we try to sketch the evolution of GI, focusing mainly on the basic idea, the properties and superiority,progress toward applications of GI with classical sources, and provide our discussion looking into the future.展开更多
We develop a theory for the magnon Kerr effect in a cavity magnonics system, consisting of magnons in a small yttrium iron garnet(YIG) sphere strongly coupled to cavity photons, and use it to study the bistability in ...We develop a theory for the magnon Kerr effect in a cavity magnonics system, consisting of magnons in a small yttrium iron garnet(YIG) sphere strongly coupled to cavity photons, and use it to study the bistability in this hybrid system. To have a complete picture of the bistability phenomenon, we analyze two different cases in driving the cavity magnonics system, i.e.,directly pumping the YIG sphere and the cavity, respectively. In both cases, the magnon frequency shifts due to the Kerr effect exhibit a similar bistable behavior but the corresponding critical powers are different. Moreover, we show how the bistability of the system can be demonstrated using the transmission spectrum of the cavity. Our results are valid in a wide parameter regime and generalize the theory of bistability in a cavity magnonics system.展开更多
We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride(BaF)molecules in a 4 K cryogenic cell.The obtained spectra with a resolution of 19...We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride(BaF)molecules in a 4 K cryogenic cell.The obtained spectra with a resolution of 19 MHz,much smaller than previously observed in absorption spectroscopy,clearly resolve the hyperfine transitions.Moreover,we use these high-resolution spectra to fit the hyperfine splittings of excited A(v=0)state and find the hyperfine splitting of the laser-cooling-relevant A^(2)Π_(1/2)(v=0,J=1/2,+)state is about 18 MHz,much higher than the previous theoretically predicted value.This provides important missing information for laser cooling of BaF molecules.展开更多
Correlation imaging is attracting more and more at tent ion as a novel imaging technique taking advantage of the high-order coherence of light fields.To reconstruct an image oi the object,many frames of different spec...Correlation imaging is attracting more and more at tent ion as a novel imaging technique taking advantage of the high-order coherence of light fields.To reconstruct an image oi the object,many frames of different speckle patterns are required.Therefore,the speed of imaging is strongly limited by the speed of the refreshing rate of the light field.We propose a coprime-frequencied sinusoidal modulation method for speckle pattern creation using a spatial light modulator in a computational ghost imaging system to increase the speed of imaging.The performance of the proposed method is discussed as well.展开更多
Due to the similar physical and chemical properties, isotopes are usually hard to separate. On the other hand, the isotope shifts are very well separated in a high-resolution spectrum, making them possible to be addre...Due to the similar physical and chemical properties, isotopes are usually hard to separate. On the other hand, the isotope shifts are very well separated in a high-resolution spectrum, making them possible to be addressed individually by lasers, thus separated. Here we report such an isotope separation experiment with Potassium atoms. The isotopes are independently optical pumped to the desired spin states, and then separated with a Stern–Gerlach scheme. A micro-capillary oven is used to collimate the atomic beam, and a Halbach-type magnet array is used to deflect the desired atoms. Finally, the 40K is enriched by two orders of magnitude. This magneto–optical combined method provides an effective way to separate isotopes and can be extended to other elements if the relevant optical pumping scheme is feasible.展开更多
Disorder and localization have dramatic influence on the topological properties of a quantum system.While strong disorder can close the band gap thus depriving topological materials of topological features,disorder ma...Disorder and localization have dramatic influence on the topological properties of a quantum system.While strong disorder can close the band gap thus depriving topological materials of topological features,disorder may also induce topology from trivial band structures,wherein topological invariants are shared by completely localized states.Here we experimentally investigate a fundamentally distinct scenario where topology is identified in a critically localized regime,with eigenstates neither fully extended nor completely localized.Adopting the technique of momentum-lattice engineering for ultracold atoms,we implement a one-dimensional,generalized Aubry-Andrémodel with both diagonal and off-diagonal quasi-periodic disorder in momentum space,and characterize its localization and topological properties through dynamic observables.We then demonstrate the impact of interactions on the critically localized topological state,as a first experimental endeavor toward the clarification of many-body critical phase,the critical analogue of the many-body localized state.展开更多
Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms...Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms.Photonic accelerators are designed to accelerate specific categories of computing in the optical domain,especially matrix multiplication,to address the growing demand for computing resources and capacity.Photonic matrix multiplication has much potential to expand the domain of telecommunication,and artificial intelligence benefiting from its superior performance.Recent research in photonic matrix multiplication has flourished and may provide opportunities to develop applications that are unachievable at present by conventional electronic processors.In this review,we first introduce the methods of photonic matrix multiplication,mainly including the plane light conversion method,Mach–Zehnder interferometer method and wavelength division multiplexing method.We also summarize the developmental milestones of photonic matrix multiplication and the related applications.Then,we review their detailed advances in applications to optical signal processing and artificial neural networks in recent years.Finally,we comment on the challenges and perspectives of photonic matrix multiplication and photonic acceleration.展开更多
Applications of ghost imaging are limited by the requirement on a large number of samplings. Based on the observation that the edge area contains more information thus requiring a larger number of samplings, we propos...Applications of ghost imaging are limited by the requirement on a large number of samplings. Based on the observation that the edge area contains more information thus requiring a larger number of samplings, we propose a feedback ghost imaging strategy to reduce the number of required samplings. The field of view is gradually concentrated onto the edge area,with the size of illumination speckles getting smaller. Experimentally, images of high quality and resolution are successfully reconstructed with much fewer samplings and linear algorithm.展开更多
We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magneti...We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magnetic field decomposes the multi-level system into several two-level sub-systems,hence the stimulated absorption and stimulated emission can occur in order,allowing for the multiple photon momentum transfer.We show that this scheme also works on the laser-coolable molecules with a better cooling effect compared to the conventional Doppler cooling.A reduced dependence on spontaneous emission based on our scheme is observed as well.Our results suggest this scheme is very feasible for laser cooling of polar molecules.展开更多
We propose an experimentally realizable nonreciprocal magnonic device at the single-magnon level by exploiting magnon block-ade in a magnon-based hybrid system.The coherent qubit-magnon coupling,mediated by virtual ph...We propose an experimentally realizable nonreciprocal magnonic device at the single-magnon level by exploiting magnon block-ade in a magnon-based hybrid system.The coherent qubit-magnon coupling,mediated by virtual photons in a microwave cavity,leads to the energy-level anharmonicity of the composite modes.In contrast,the corresponding dissipative counterpart,induced by traveling microwaves in a waveguide,yields inhomogeneous broadenings of the energy levels.As a result,the cooperative effects of these two kinds of interactions give rise to the emergence of the direction-dependent magnon blockade.We show that this can be demonstrated by studying the equal-time second-order correlation function of the magnon mode.Our study opens an avenue to engineer nonreciprocal magnonic devices in the quantum regime involving only a small number of magnons.展开更多
Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2...Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2 Se_3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi_2 Se_3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.展开更多
Cavity magnomechanics has recently become a new platform for studying macroscopic quantum phenomena.The magnetostriction induced vibration mode of a large-size ferromagnet or ferrimagnet reaching its ground state repr...Cavity magnomechanics has recently become a new platform for studying macroscopic quantum phenomena.The magnetostriction induced vibration mode of a large-size ferromagnet or ferrimagnet reaching its ground state represents a genuine macroscopic quantum state.Here we study the ground-state cooling of the mechanical vibration mode in a cavity magnomechanical system,and focus on the role of magnon squeezing in improving the cooling efficiency.The magnon squeezing is obtained by exploiting the magnon self-Kerr nonlinearity.We find that the magnon squeezing can significantly and even completely suppress the magnomechanical Stokes scattering.It thus becomes particularly useful in realizing ground-state cooling in the unresolved-sideband regime,where the conventional sideband cooling protocols become inefficient.We also find that the coupling to the microwave cavity plays only an adverse effect in mechanical cooling.This makes essentially the two-mode magnomechanical system(without involving the microwave cavity)a preferred system for cooling the mechanical motion,in which the magnon mode is established by a uniform bias magnetic field and a microwave drive field.展开更多
In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La2Cu O4 and metallic La2-xSrxCuO4(x=0.45). An interesting question to address is how general and ...In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La2Cu O4 and metallic La2-xSrxCuO4(x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La2CuO4 and La2-xSrxCuO4 by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present1.70(the nominal Sr content in the targets). X-ray diffraction result indicates that our La2-xSrxCuO4 films with x≤0.60 have very high crystalline quality;but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x^0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.展开更多
基金Project supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grants Nos.2017YFA0303002and 2016YFA0300204)the Fundamental Research Funds for the Central Universities,China
文摘In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11934010,U1801661,U1930402,and 11847087)the National Key Research and Development Program of China(Grant No.2016YFA0301200)。
文摘We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In our proposal,we use a dissipative TLS ensemble and an active cavity with effective gain.In the weak drive-field limit,the QPT can occur under the combined actions of the loss and gain of the system.Owing to the active cavity,the QPT behavior can be much differentiated even for a finite strength of the drive field on the TLS ensemble.Also,we propose to implement our scheme based on the dissipative nitrogen-vacancy(NV)centers coupled to an active optical cavity made from the gainmedium-doped silica.Furthermore,we show that the QPT can be measured by probing the transmission spectrum of the cavity embedding the ensemble of the NV centers.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11934010,U1801661,and 12174329)the Zhejiang Province Program for Science and Technology(Grant No.2020C01019)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2021FZZX001-02)the China Postdoctoral Science Foundation(Grant No.2019M660137)
文摘When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show the nonlinearity and heating-induced frequency shifts of the Kittel mode and HMS mode in a yttrium-iron-garnet(YIG)sphere.When the Kittel mode is driven to generate a certain number of excitations,the temperature of the whole YIG sample rises and the HMS mode can display an induced frequency shift,and vice versa.This cross effect provides a new method to study the magnetization dynamics and paves a way for novel cavity magnonic devices by including the heating effect as an operational degree of freedom.
基金supported by the National Natural Science Foundation of China(Grant Nos.91436103,91536102,and 91336211)the Research Programme of National University of Defense Technology,China(Grant No.JC15-0203)the Strategic Priority Research Programme of the Chinese Academy of Sciences(Grant No.XDB21030300)
文摘Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the 3d ^2D3/2-3d ^2D5/2 transition in the potassium-like （K-like） sequence with 26 ≤ Z ≤ 36 are investigated by using the multi-configuration Dirac-Hartree-Fock （MCDHF） method. The contributions of the electron correlations, Breit interaction, and the leading-order quantum electrodynamic （QED） effects on the transition properties are analyzed. The present results are interested in the laboratory tokamak and the astronomical observations. Furthermore, the feasibility of these ions for the highly charged ion （HCI） clocks is discussed. Considering the wavelength of lasers and manipulation process of the atomic clocks, Cu^10＋ and Zn^11＋ are recommended as promising candidates with achievable quality factors at the 10^15 level.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91436103,11404025,and 91536106)the Research Program of National University of Defense Technology,China(Grant No.JC15-0203)the China Postdoctoral Science Foundation(Grant No.2014M560061)
文摘Accurate isotope shift factors of the 2s2p^（3,1）P_1~o–2s^2 ~1S_0 transitions in B II, obtained with the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods, are reported. We found a linear correlation relation between the mass shift factors and the energies for the transitions concerned, considering all-order electron correlations. This relation is important for estimating the uncertainty in the calculation of isotope shift factors. These atomic data can be used to extract the nuclear mean-square charge radii of the boron isotopes with halo structures or to resolve the high precise spectroscopy of B II in astronomical observation.
基金supported by the National Natural Science Foundation of China (Nos.62105365,62275270,and 62001484)Science Fund for Distinguished Young Scholars of Hunan Province (No.2021JJ10051)Research Program of National University of Defense Technology (Nos.ZK21-11 and ZK22-58)。
文摘Ghost imaging has been attracting more and more attention, which provides a way to obtain images of objects with only a single-pixel detector. Considering possible applications, it becomes urgent to clarify the sensitivity of ghost imaging. Due to the unique characteristics of single-pixel detectors, which collect photons without distributing them to multiple pixels,often outperforming array sensors, ghost imaging is believed to be more sensitive than conventional imaging. However,a systematic analysis on the sensitivity of ghost imaging is yet to be completed. In this paper, we present a method for quantitatively assessing the sensitivity of ghost imaging. A detailed comparison is provided between ghost imaging and conventional imaging, taking into account the particle nature of photons and the noise of detection. With the settings of the two imaging methods being the same to the most extent, the minimal required number of detected photons for images of a certain quality is considered. For the thermal source version, ghost imaging demonstrates enhanced sensitivity under practical situations, with noise considered.Employing an entangled source, ghost imaging surpasses conventional imaging techniques in terms of sensitivity obviously. In one word, ghost imaging promises higher sensitivity at low photon flux and noisy situations.
基金supported by the National Natural Science Foundation of China (Nos.62275270 and 62105365)the Science Fund for Distinguished Young Scholars of Hunan Province (No.2021JJ10051)+1 种基金the Natural Science Research of Jiangsu Higher Education Institutions of China (No.21KJA140001)the Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province,Soochow University (No.ZZ2307)。
文摘Study on optical correlation function initiates the development of many quantum techniques, with ghost imaging(GI) being one of the great achievements. Upon the first demonstration with entangled sources, the physics and improvements of GI attracted much interest. Among existing studies, GI with classical sources provoked debates and ideas to the most extent.Toward better understanding and practical applications of GI, fundamental theory, various designs of illumination patterns as well as reconstruction algorithms, demonstrations and field tests have been reported, with the topic of GI very much enriched. In this paper, we try to sketch the evolution of GI, focusing mainly on the basic idea, the properties and superiority,progress toward applications of GI with classical sources, and provide our discussion looking into the future.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFA0301200)the National Natural Science Foundation of China(Grant Nos.11774022,and U1530401)
文摘We develop a theory for the magnon Kerr effect in a cavity magnonics system, consisting of magnons in a small yttrium iron garnet(YIG) sphere strongly coupled to cavity photons, and use it to study the bistability in this hybrid system. To have a complete picture of the bistability phenomenon, we analyze two different cases in driving the cavity magnonics system, i.e.,directly pumping the YIG sphere and the cavity, respectively. In both cases, the magnon frequency shifts due to the Kerr effect exhibit a similar bistable behavior but the corresponding critical powers are different. Moreover, we show how the bistability of the system can be demonstrated using the transmission spectrum of the cavity. Our results are valid in a wide parameter regime and generalize the theory of bistability in a cavity magnonics system.
基金support from the National Key Research and Development Program of China under Grant No.2018YFA0307200the National Natural Science Foundation of China under Grant Nos.U21A20437 and 12074337+2 种基金the Natural Science Foundation of Zhejiang Province under Grant No.LR21A040002Zhejiang Province Plan for Science and technology No.2020C01019the Fundamental Research Funds for the Central Universities under No.2021FZZX001-02.
文摘We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride(BaF)molecules in a 4 K cryogenic cell.The obtained spectra with a resolution of 19 MHz,much smaller than previously observed in absorption spectroscopy,clearly resolve the hyperfine transitions.Moreover,we use these high-resolution spectra to fit the hyperfine splittings of excited A(v=0)state and find the hyperfine splitting of the laser-cooling-relevant A^(2)Π_(1/2)(v=0,J=1/2,+)state is about 18 MHz,much higher than the previous theoretically predicted value.This provides important missing information for laser cooling of BaF molecules.
基金supported by the National Natural Science Foundation of China under Grant No.11374368supported by the Program for New Century Excellent Talents in University
文摘Correlation imaging is attracting more and more at tent ion as a novel imaging technique taking advantage of the high-order coherence of light fields.To reconstruct an image oi the object,many frames of different speckle patterns are required.Therefore,the speed of imaging is strongly limited by the speed of the refreshing rate of the light field.We propose a coprime-frequencied sinusoidal modulation method for speckle pattern creation using a spatial light modulator in a computational ghost imaging system to increase the speed of imaging.The performance of the proposed method is discussed as well.
基金We acknowledge the support from the National Key R&D Program of China under Grant No.2018YFA0307200the National Natural Science Foundation of China under Grant No.12074337+2 种基金the Natural Science Foundation of Zhejiang Province under Grant Nos.LR21A040002 and LZ18A040001Zhejiang Province Plan for Science and Technology No.2020C01019the Fundamental Research Funds for the Central Universities under Grant Nos.2020XZZX002-05 and 2021FZZX001-02.
文摘Due to the similar physical and chemical properties, isotopes are usually hard to separate. On the other hand, the isotope shifts are very well separated in a high-resolution spectrum, making them possible to be addressed individually by lasers, thus separated. Here we report such an isotope separation experiment with Potassium atoms. The isotopes are independently optical pumped to the desired spin states, and then separated with a Stern–Gerlach scheme. A micro-capillary oven is used to collimate the atomic beam, and a Halbach-type magnet array is used to deflect the desired atoms. Finally, the 40K is enriched by two orders of magnitude. This magneto–optical combined method provides an effective way to separate isotopes and can be extended to other elements if the relevant optical pumping scheme is feasible.
基金the National Key Research and Development Program of China(2018YFA0307200,2016YFA0301700 and 2017YFA0304100)the National Natural Science Foundation of China(12074337 and 11974331)+2 种基金Natural Science Foundation of Zhejiang Province(LR21A040002 and LZ18A040001)Zhejiang Provincial Plan for Science and Technology(2020C01019)the Fundamental Research Funds for the Central Universities(2020XZZX002-05 and 2021FZZX001-02)。
文摘Disorder and localization have dramatic influence on the topological properties of a quantum system.While strong disorder can close the band gap thus depriving topological materials of topological features,disorder may also induce topology from trivial band structures,wherein topological invariants are shared by completely localized states.Here we experimentally investigate a fundamentally distinct scenario where topology is identified in a critically localized regime,with eigenstates neither fully extended nor completely localized.Adopting the technique of momentum-lattice engineering for ultracold atoms,we implement a one-dimensional,generalized Aubry-Andrémodel with both diagonal and off-diagonal quasi-periodic disorder in momentum space,and characterize its localization and topological properties through dynamic observables.We then demonstrate the impact of interactions on the critically localized topological state,as a first experimental endeavor toward the clarification of many-body critical phase,the critical analogue of the many-body localized state.
基金Chaoran Huang would like to thank Alexander Tait,Bhavin Shastri and Paul Prucnal for the fruitful discussions.J.J.D.acknowledges the support of the National Key Research and Development Project of China(2018YFB2201901)the National Natural Science Foundation of China(61805090,62075075).
文摘Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms.Photonic accelerators are designed to accelerate specific categories of computing in the optical domain,especially matrix multiplication,to address the growing demand for computing resources and capacity.Photonic matrix multiplication has much potential to expand the domain of telecommunication,and artificial intelligence benefiting from its superior performance.Recent research in photonic matrix multiplication has flourished and may provide opportunities to develop applications that are unachievable at present by conventional electronic processors.In this review,we first introduce the methods of photonic matrix multiplication,mainly including the plane light conversion method,Mach–Zehnder interferometer method and wavelength division multiplexing method.We also summarize the developmental milestones of photonic matrix multiplication and the related applications.Then,we review their detailed advances in applications to optical signal processing and artificial neural networks in recent years.Finally,we comment on the challenges and perspectives of photonic matrix multiplication and photonic acceleration.
基金supported by the National Natural Science Foundation of China (Nos. 11774431 and 61701511)。
文摘Applications of ghost imaging are limited by the requirement on a large number of samplings. Based on the observation that the edge area contains more information thus requiring a larger number of samplings, we propose a feedback ghost imaging strategy to reduce the number of required samplings. The field of view is gradually concentrated onto the edge area,with the size of illumination speckles getting smaller. Experimentally, images of high quality and resolution are successfully reconstructed with much fewer samplings and linear algorithm.
基金the Natural Science Foundation of Zhejiang Province under Grant No.LZ18A040001the National Key R&D Program of China under Grant No.2018YFA0307200+2 种基金the National Natural Science Foundation of China under Grant No.12074337Zhejiang Province Plan for Science and Technology No.2020C01019the Fundamental Research Funds for the Central Universities.
文摘We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magnetic field decomposes the multi-level system into several two-level sub-systems,hence the stimulated absorption and stimulated emission can occur in order,allowing for the multiple photon momentum transfer.We show that this scheme also works on the laser-coolable molecules with a better cooling effect compared to the conventional Doppler cooling.A reduced dependence on spontaneous emission based on our scheme is observed as well.Our results suggest this scheme is very feasible for laser cooling of polar molecules.
基金supported by the National Natural Science Foundation of China(Grant Nos.11934010,U1801661,and U21A20436)National Key Research and Development Program of China(Grant No.2016YFA0301200)+1 种基金Zhejiang Province Program for Science and Technology(Grant No.2020C01019)supported by the National Natural Science Foundation of China(Grant No.11804074)。
文摘We propose an experimentally realizable nonreciprocal magnonic device at the single-magnon level by exploiting magnon block-ade in a magnon-based hybrid system.The coherent qubit-magnon coupling,mediated by virtual photons in a microwave cavity,leads to the energy-level anharmonicity of the composite modes.In contrast,the corresponding dissipative counterpart,induced by traveling microwaves in a waveguide,yields inhomogeneous broadenings of the energy levels.As a result,the cooperative effects of these two kinds of interactions give rise to the emergence of the direction-dependent magnon blockade.We show that this can be demonstrated by studying the equal-time second-order correlation function of the magnon mode.Our study opens an avenue to engineer nonreciprocal magnonic devices in the quantum regime involving only a small number of magnons.
基金supported by the Opening Foundation of State Key Laboratory of High Performance Computing(Nos.201601-01,201601-02,and 201601-03)the Scientific Researches Foundation of National University of Defense Technology(No.zk16-03-59)+3 种基金the Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2017KF06)the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2018ZR05)the Funds for International Cooperation and Exchange of National Natural Science Foundation of China(Nos.61120106 and 60921062)the National Natural Science Foundation of China(Nos.11802339 and 11805276)
文摘Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2 Se_3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi_2 Se_3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.
基金supported by Zhejiang Province Program for Science and Technology(2020C01019)the National Natural Science Foundation of China(U1801661,11874249,11934010,12174329).
文摘Cavity magnomechanics has recently become a new platform for studying macroscopic quantum phenomena.The magnetostriction induced vibration mode of a large-size ferromagnet or ferrimagnet reaching its ground state represents a genuine macroscopic quantum state.Here we study the ground-state cooling of the mechanical vibration mode in a cavity magnomechanical system,and focus on the role of magnon squeezing in improving the cooling efficiency.The magnon squeezing is obtained by exploiting the magnon self-Kerr nonlinearity.We find that the magnon squeezing can significantly and even completely suppress the magnomechanical Stokes scattering.It thus becomes particularly useful in realizing ground-state cooling in the unresolved-sideband regime,where the conventional sideband cooling protocols become inefficient.We also find that the coupling to the microwave cavity plays only an adverse effect in mechanical cooling.This makes essentially the two-mode magnomechanical system(without involving the microwave cavity)a preferred system for cooling the mechanical motion,in which the magnon mode is established by a uniform bias magnetic field and a microwave drive field.
基金supported by the National Key Research and Development Program of Ministry of Science and Technology of China (2017YFA0303002, 2016YFA0300204, and 2016YFA0300701)the Fundamental Research Funds for the Central Universities
文摘In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La2Cu O4 and metallic La2-xSrxCuO4(x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La2CuO4 and La2-xSrxCuO4 by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present1.70(the nominal Sr content in the targets). X-ray diffraction result indicates that our La2-xSrxCuO4 films with x≤0.60 have very high crystalline quality;but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x^0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.
