We investigate the quantum squeezing of matter-wave solitons in atomic Bose-Einstein condensates.By calculating quantum fluctuations of the solitons via solving the Bogoliubov-de Gennes equations,we show that signific...We investigate the quantum squeezing of matter-wave solitons in atomic Bose-Einstein condensates.By calculating quantum fluctuations of the solitons via solving the Bogoliubov-de Gennes equations,we show that significant quantum squeezing can be realized for both bright and dark solitons.We also show that the squeezing efficiency of the solitons can be enhanced and manipulated by atom-atom interaction and soliton blackness.The results reported here are beneficial not only for understanding quantum property of matter-wave solitons,but also for promising applications of Bose-condensed quantum gases.展开更多
We study the magneto-optical conductivity of a number of van der Waals heterostructures,namely,twisted bilayer graphene,AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked b...We study the magneto-optical conductivity of a number of van der Waals heterostructures,namely,twisted bilayer graphene,AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride.As the magnetic field increases,the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum.Whilst twisted bilayer graphene displays only weak circular dichroism,the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer.As the left and right circularly polarized light interact with these structures differently,plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted.The size of the respective angles is on the order of a degree.展开更多
We report the generation of a crossed,focused,optical vortex beam by using a pair of hybrid holograms,which combine the vortex phase and lens phase onto a spatial light modulator.We study the intensity distributions o...We report the generation of a crossed,focused,optical vortex beam by using a pair of hybrid holograms,which combine the vortex phase and lens phase onto a spatial light modulator.We study the intensity distributions of the vortex beam in free propagation space,and the relationship of its dark spot size with the incident Gaussian beam’s waist,the lens’s focal length,and its orbital angular momentum.Our results show that the crossed,focused,vortex beam’s dark spot size can be as small as 16.3μm and adjustable by the quantum number of the orbital angular momentum,and can be used to increase the density of trapped molecules.Furthermore,we calculate the optical potential of the blue-detuned,crossed vortex beam for MgF molecules.It is applicable to cool and trap neutral molecules by intensity-gradient-induced Sisyphus cooling,as the intensity gradient of such vortex beam is extremely high near the focal point.展开更多
We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these...We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these fragment ions S~＋, S^（2＋）, CS~＋, and CS^（2＋）by breaking one C–S bond, and assign their Coulomb explosion channels by considering their kinetic energy release and angular distribution. We also numerically simulate the dissociation dynamics of parent ions CS_2^（k＋）（k = 2–4） by a Coulomb potential approximation, and obtain the time evolution of Coulomb energy and kinetic energy release, which indicates that the dissociation time of parent ions CS_2^（k＋） decreases with the increase of the charge number k.These experimental and theoretical results can serve as a useful benchmark for those researchers who work in the related area.展开更多
An ultrafast electron diffraction technique with both high temporal and spatial resolution has been shown to be a powerful tool to observe the material transient structural change on an atomic scale.The space charge f...An ultrafast electron diffraction technique with both high temporal and spatial resolution has been shown to be a powerful tool to observe the material transient structural change on an atomic scale.The space charge forces in a multi-electron bunch will greatly broaden the electron pulse width,and therefore limit the temporal resolution of the high brightness electron pulse.Here in this work,we design an ultrafast electron diffraction system,and utilize a radio frequency cavity to realize the ultrafast electron pulse compression.We experimentally demonstrate that the stretched electron pulse width of14.98 ps with an electron energy of 40 keV and the electron number of 1.0 ×10;can be maximally compressed to about0.61 ps for single-pulse measurement and 2.48 ps for multi-pulse measurement by using a 3.2-GHz radiofrequency cavity.We also theoretically and experimentally analyze the parameters influencing the electron pulse compression efficiency for single-and multi-pulse measurements by considering radiofrequency field time jitter,electron pulse time jitter and their relative time jitter.We suggest that increasing the electron energy or shortening the distance between the compression cavity and the streak cavity can further improve the electron pulse compression efficiency.These experimental and theoretical results are very helpful for designing the ultrafast electron diffraction experiment equipment and compressing the ultrafast electron pulse width in a future study.展开更多
Orbital angular momentums(OAMs)greatly enhance the channel capacity in free-space optical communication.However,demodulation of superposed OAM to recognize them separately is always difficult,especially upon multiplex...Orbital angular momentums(OAMs)greatly enhance the channel capacity in free-space optical communication.However,demodulation of superposed OAM to recognize them separately is always difficult,especially upon multiplexing more OAMs.In this work,we report a directly recognition of multiplexed fractional OAM modes,without separating them,at a resolution of 0.1 with high accuracy,using a multi-task deep learning(MTDL)model,which has not been reported before.Namely,two-mode,four-mode,and eight-mode superposed OAM beams,experimentally generated with a hologram carrying both phase and amplitude information,are well recognized by the suitable MTDL model.Two applications in information transmission are presented:the first is for 256-ary OAM shift keying via multiplexed fractional OAMs;the second is for OAM division multiplexed information transmission in an eightfold speed.The encouraging results will expand the capacity in future free-space optical communication.展开更多
Lu:Hello,Prof.Haroche,nice to see you again!Let us start the interview.In 2012,you and David Wineland won the Nobel Prize in Physics.Can you describe your work in simple terms to a general audience?And can you tell us...Lu:Hello,Prof.Haroche,nice to see you again!Let us start the interview.In 2012,you and David Wineland won the Nobel Prize in Physics.Can you describe your work in simple terms to a general audience?And can you tell us how you were originally interested in this field and got into this study?Haroche:Maybe I should start with the second part of the question.I got interested in atomic physics when I was a student atÉcole Normale Supérieure(ENS)in Paris in the 1960s.展开更多
Gaussian Boson sampling(GBS) provides a highly efficient approach to make use of squeezed states from parametric down-conversion to solve a classically hard-to-solve sampling problem. The GBS protocol not only signifi...Gaussian Boson sampling(GBS) provides a highly efficient approach to make use of squeezed states from parametric down-conversion to solve a classically hard-to-solve sampling problem. The GBS protocol not only significantly enhances the photon generation probability, compared to standard Boson sampling with single photon Fock states, but also links to potential applications such as dense subgraph problems and molecular vibronic spectra. Here, we report the first experimental demonstration of GBS using squeezed-state sources with simultaneously high photon indistinguishability and collection efficiency.We implement and validate 3-, 4- and 5-photon GBS with high sampling rates of 832, 163 and 23 kHz,respectively, which is more than 4.4, 12.0, and 29.5 times faster than the previous experiments.Further, we observe a quantum speed-up on a NP-hard optimization problem when comparing with simulated thermal sampler and uniform sampler.展开更多
Here we propose a scheme to slow MgF molecules by using EOM-based frequency-chirped radiation pressure slowing.The scheme well addresses the need for a rapid chirp rate while light molecules are being laser slowed,who...Here we propose a scheme to slow MgF molecules by using EOM-based frequency-chirped radiation pressure slowing.The scheme well addresses the need for a rapid chirp rate while light molecules are being laser slowed,whose scattering rate and recoil velocity are large.Two EOMs are used to compensate the rapidly changing Doppler shifts arised from the movement of molecules,and to cover the hyperfine energy structure of MgF,respectively.Based the scattering rate maps calculated from an optical Bloch equation model,individual molecule trajectories are simulated by using a semi-classical three-dimensional Monte Carlo approach.We show how the modulation configuration of EOM and the magnetic field influence the slowing results.The study shows that a cryogenic buffer gas-cooled MgF beam source is possible to be slowed down with a number of∼1.4×10^(6)–10^(7),and the final forward speed peaks at∼10 m/s near the capture velocity of a molecular MOT.展开更多
In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with ...In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with Purcell enhancement),interconnectivity with spin qubits,and a scalable on-chip platform.However,in the past two decades,the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%,and the distances were limited from a few meters to kilometers.Here,we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber.The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities.Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band.The observed interference visibility is 0.670.02(0.930.04)without(with)temporal filtering.Feasible improvements can further extend the distance to∼600 km.Our work represents a key step to long-distance solid-state quantum networks.展开更多
Electromagnetically induced transparency(EIT), a typical quantum interference effect, has been extensively investigated in coherent atomic gases. In recent years, it has been recognized that the plasmonic analog of at...Electromagnetically induced transparency(EIT), a typical quantum interference effect, has been extensively investigated in coherent atomic gases. In recent years, it has been recognized that the plasmonic analog of atomic EIT, called plasmon-induced transparency(PIT), is a fruitful platform for the study of EIT-like propagation and interaction of plasmonic polaritons. Many proposals have been presented for realizing PIT in various metamaterials, which possess many unique characters, including the suppression of absorption of electromagnetic radiation, the reduction of propagation velocity, etc. Especially, nonlinear PIT metamaterials, obtained usually by embedding nonlinear elements into meta-atoms, can be used to acquire an enhanced Kerr effect resulted from the resonant coupling between radiation and the meta-atoms and to actively manipulate structural and dynamical properties of plasmonic metamaterials. In this article, we review recent research progress in nonlinear PIT metamaterials, and elucidate their interesting properties and promising applications. In particular, we give a detailed description on the propagation and interaction of nonlinear plasmonic polaritons in metamaterials via PIT,which are promising for chip-scale applications in information processing and transmission.展开更多
Light bullets(LBs)are localized nonlinear waves propagating in high spatial dimensions.Finding stable LBs and realizing their control are desirable due to the interesting physics and potential applications.Here,we sho...Light bullets(LBs)are localized nonlinear waves propagating in high spatial dimensions.Finding stable LBs and realizing their control are desirable due to the interesting physics and potential applications.Here,we show that nonlocal LBs generated in a cold Rydberg atomic gas via the balance among the dispersion,diffraction,and giant nonlocal Kerr nonlinearity contributed by long-range Rydberg-Rydberg interaction can be actively manipulated by using a weak gradient magnetic field.Nonlocal LBs are generated by a balance among dispersion,diffraction,and large nonlocal Kerr nonlinearities contributed by long-range Rydberg-Rydberg interactions.Here,we find that active manipulation can be achieved by weak gradient magnetic fields in cold Rydberg atomic gases.Especially,the LBs may undergo significant Stern-Gerlach deflections,and their motion trajectories can be controlled by adjusting the magnetic-field gradient.The results reported here are helpful not only for understanding unique properties of LBs in nonlocal optical media but also for finding ways for precision measurements of magnetic fields.展开更多
Patterns resulted from modulation instability are ubiquitous and have been extensively studied in optics and Bose-Einstein condensates. However, these patterns have not been realized in ultracold Fermi gases, although...Patterns resulted from modulation instability are ubiquitous and have been extensively studied in optics and Bose-Einstein condensates. However, these patterns have not been realized in ultracold Fermi gases, although there has been considerable theoretical interest in this field. Here we report an experimental observation of space-time patterns in a superfluid Fermi gas excited by red-detuned laser light. Longitudinal spatially fluctuated laser beams induce the spontaneous formation of two different kinds of patterns. For strongly interacting Fermi gas, the induced patterns accompanied by phonon excitations demonstrate a striking"X"-type dispersion relation between frequency and wavevector. Then, the propagation of such patterns in the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer crossover is investigated, which is related to the speed of sound and agrees well with theoretical calculations. The observed patterns in noninteracting Fermi gases are stationary without phonon excitations and show a much longer lifetime.展开更多
Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles ca...Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11975098)。
文摘We investigate the quantum squeezing of matter-wave solitons in atomic Bose-Einstein condensates.By calculating quantum fluctuations of the solitons via solving the Bogoliubov-de Gennes equations,we show that significant quantum squeezing can be realized for both bright and dark solitons.We also show that the squeezing efficiency of the solitons can be enhanced and manipulated by atom-atom interaction and soliton blackness.The results reported here are beneficial not only for understanding quantum property of matter-wave solitons,but also for promising applications of Bose-condensed quantum gases.
基金the National Natural Science Foundation of China(Grant Nos.12050410228 and 12074260)the Fund from the Science and Technology Commission of Shanghai Municipality,China(Grant No.19ZR1436400)。
文摘We study the magneto-optical conductivity of a number of van der Waals heterostructures,namely,twisted bilayer graphene,AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride.As the magnetic field increases,the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum.Whilst twisted bilayer graphene displays only weak circular dichroism,the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer.As the left and right circularly polarized light interact with these structures differently,plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted.The size of the respective angles is on the order of a degree.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11834003 and 91836103).
文摘We report the generation of a crossed,focused,optical vortex beam by using a pair of hybrid holograms,which combine the vortex phase and lens phase onto a spatial light modulator.We study the intensity distributions of the vortex beam in free propagation space,and the relationship of its dark spot size with the incident Gaussian beam’s waist,the lens’s focal length,and its orbital angular momentum.Our results show that the crossed,focused,vortex beam’s dark spot size can be as small as 16.3μm and adjustable by the quantum number of the orbital angular momentum,and can be used to increase the density of trapped molecules.Furthermore,we calculate the optical potential of the blue-detuned,crossed vortex beam for MgF molecules.It is applicable to cool and trap neutral molecules by intensity-gradient-induced Sisyphus cooling,as the intensity gradient of such vortex beam is extremely high near the focal point.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51132004 and 11474096)the Science and Technology Commission of Shanghai Municipality,China(Grant No.14JC1401500)the support of the NYU-ECNU Institute of Physics at NYU Shanghai,China
文摘We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these fragment ions S~＋, S^（2＋）, CS~＋, and CS^（2＋）by breaking one C–S bond, and assign their Coulomb explosion channels by considering their kinetic energy release and angular distribution. We also numerically simulate the dissociation dynamics of parent ions CS_2^（k＋）（k = 2–4） by a Coulomb potential approximation, and obtain the time evolution of Coulomb energy and kinetic energy release, which indicates that the dissociation time of parent ions CS_2^（k＋） decreases with the increase of the charge number k.These experimental and theoretical results can serve as a useful benchmark for those researchers who work in the related area.
基金Project partially supported by the National Natural Science Foundation of China(Grant Nos.51132004 and 11474096)the Fund from the Science and Technology Commission of Shanghai Municipality,China(Gant No.14JC1401500)the NYU-ECNU Institute of Physics at NYU Shanghai,China
文摘An ultrafast electron diffraction technique with both high temporal and spatial resolution has been shown to be a powerful tool to observe the material transient structural change on an atomic scale.The space charge forces in a multi-electron bunch will greatly broaden the electron pulse width,and therefore limit the temporal resolution of the high brightness electron pulse.Here in this work,we design an ultrafast electron diffraction system,and utilize a radio frequency cavity to realize the ultrafast electron pulse compression.We experimentally demonstrate that the stretched electron pulse width of14.98 ps with an electron energy of 40 keV and the electron number of 1.0 ×10;can be maximally compressed to about0.61 ps for single-pulse measurement and 2.48 ps for multi-pulse measurement by using a 3.2-GHz radiofrequency cavity.We also theoretically and experimentally analyze the parameters influencing the electron pulse compression efficiency for single-and multi-pulse measurements by considering radiofrequency field time jitter,electron pulse time jitter and their relative time jitter.We suggest that increasing the electron energy or shortening the distance between the compression cavity and the streak cavity can further improve the electron pulse compression efficiency.These experimental and theoretical results are very helpful for designing the ultrafast electron diffraction experiment equipment and compressing the ultrafast electron pulse width in a future study.
基金Financial supports are from the National Natural Science Foundation of China(Grant Nos.12174115,91836103,and 11834003).
文摘Orbital angular momentums(OAMs)greatly enhance the channel capacity in free-space optical communication.However,demodulation of superposed OAM to recognize them separately is always difficult,especially upon multiplexing more OAMs.In this work,we report a directly recognition of multiplexed fractional OAM modes,without separating them,at a resolution of 0.1 with high accuracy,using a multi-task deep learning(MTDL)model,which has not been reported before.Namely,two-mode,four-mode,and eight-mode superposed OAM beams,experimentally generated with a hologram carrying both phase and amplitude information,are well recognized by the suitable MTDL model.Two applications in information transmission are presented:the first is for 256-ary OAM shift keying via multiplexed fractional OAMs;the second is for OAM division multiplexed information transmission in an eightfold speed.The encouraging results will expand the capacity in future free-space optical communication.
文摘Lu:Hello,Prof.Haroche,nice to see you again!Let us start the interview.In 2012,you and David Wineland won the Nobel Prize in Physics.Can you describe your work in simple terms to a general audience?And can you tell us how you were originally interested in this field and got into this study?Haroche:Maybe I should start with the second part of the question.I got interested in atomic physics when I was a student atÉcole Normale Supérieure(ENS)in Paris in the 1960s.
基金supported by the National Natural Science Foundation of China (91836303, 11674308, and 11525419)the Chinese Academy of Sciences, the National Fundamental Research Program (2018YFA0306100)the Anhui Initiative in Quantum Information Technologies
文摘Gaussian Boson sampling(GBS) provides a highly efficient approach to make use of squeezed states from parametric down-conversion to solve a classically hard-to-solve sampling problem. The GBS protocol not only significantly enhances the photon generation probability, compared to standard Boson sampling with single photon Fock states, but also links to potential applications such as dense subgraph problems and molecular vibronic spectra. Here, we report the first experimental demonstration of GBS using squeezed-state sources with simultaneously high photon indistinguishability and collection efficiency.We implement and validate 3-, 4- and 5-photon GBS with high sampling rates of 832, 163 and 23 kHz,respectively, which is more than 4.4, 12.0, and 29.5 times faster than the previous experiments.Further, we observe a quantum speed-up on a NP-hard optimization problem when comparing with simulated thermal sampler and uniform sampler.
基金supports are from the National Natural Science Foundation of China under Grant Nos.11834003,91836103,and 91536218.
文摘Here we propose a scheme to slow MgF molecules by using EOM-based frequency-chirped radiation pressure slowing.The scheme well addresses the need for a rapid chirp rate while light molecules are being laser slowed,whose scattering rate and recoil velocity are large.Two EOMs are used to compensate the rapidly changing Doppler shifts arised from the movement of molecules,and to cover the hyperfine energy structure of MgF,respectively.Based the scattering rate maps calculated from an optical Bloch equation model,individual molecule trajectories are simulated by using a semi-classical three-dimensional Monte Carlo approach.We show how the modulation configuration of EOM and the magnetic field influence the slowing results.The study shows that a cryogenic buffer gas-cooled MgF beam source is possible to be slowed down with a number of∼1.4×10^(6)–10^(7),and the final forward speed peaks at∼10 m/s near the capture velocity of a molecular MOT.
基金the National Natural Science Foundation of China(91836303)the National Key R&D Program of China(2019YFA0308700)+1 种基金the Chinese Academy of Sciences,the Anhui Initiative in Quantum Information Technologies,the Natural Science Foundation of Shandong Province(ZR2020LLZ007)the ShanghaiMunicipal Science and Technology Major Project(2019SHZDZX01).
文摘In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with Purcell enhancement),interconnectivity with spin qubits,and a scalable on-chip platform.However,in the past two decades,the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%,and the distances were limited from a few meters to kilometers.Here,we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber.The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities.Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band.The observed interference visibility is 0.670.02(0.930.04)without(with)temporal filtering.Feasible improvements can further extend the distance to∼600 km.Our work represents a key step to long-distance solid-state quantum networks.
基金supported by the National Natural Science Foundation of China(Nos.11174080,11475063,and 11474099)the China Postdoctoral Science Foundation(No.2017M620140)+1 种基金the International Postdoctoral Exchange Fellowship Program(No.20180040)the Shanghai Sailing Program(No.18YF1407100)
文摘Electromagnetically induced transparency(EIT), a typical quantum interference effect, has been extensively investigated in coherent atomic gases. In recent years, it has been recognized that the plasmonic analog of atomic EIT, called plasmon-induced transparency(PIT), is a fruitful platform for the study of EIT-like propagation and interaction of plasmonic polaritons. Many proposals have been presented for realizing PIT in various metamaterials, which possess many unique characters, including the suppression of absorption of electromagnetic radiation, the reduction of propagation velocity, etc. Especially, nonlinear PIT metamaterials, obtained usually by embedding nonlinear elements into meta-atoms, can be used to acquire an enhanced Kerr effect resulted from the resonant coupling between radiation and the meta-atoms and to actively manipulate structural and dynamical properties of plasmonic metamaterials. In this article, we review recent research progress in nonlinear PIT metamaterials, and elucidate their interesting properties and promising applications. In particular, we give a detailed description on the propagation and interaction of nonlinear plasmonic polaritons in metamaterials via PIT,which are promising for chip-scale applications in information processing and transmission.
基金This work was supported by the National Natural Science Foundation of China(NSFC)(Nos.11975098,11174080,and 11904104)the Shanghai Pujiang Program(No.21PJ1402500).
文摘Light bullets(LBs)are localized nonlinear waves propagating in high spatial dimensions.Finding stable LBs and realizing their control are desirable due to the interesting physics and potential applications.Here,we show that nonlocal LBs generated in a cold Rydberg atomic gas via the balance among the dispersion,diffraction,and giant nonlocal Kerr nonlinearity contributed by long-range Rydberg-Rydberg interaction can be actively manipulated by using a weak gradient magnetic field.Nonlocal LBs are generated by a balance among dispersion,diffraction,and large nonlocal Kerr nonlinearities contributed by long-range Rydberg-Rydberg interactions.Here,we find that active manipulation can be achieved by weak gradient magnetic fields in cold Rydberg atomic gases.Especially,the LBs may undergo significant Stern-Gerlach deflections,and their motion trajectories can be controlled by adjusting the magnetic-field gradient.The results reported here are helpful not only for understanding unique properties of LBs in nonlocal optical media but also for finding ways for precision measurements of magnetic fields.
基金the National Key Research and Development Program of China(Grant No.2017YFA0304201)the National Natural Science Foundation of China(Grant Nos.11925401,11734008,and 11804095)+1 种基金the Natural Science Foundation of Shanghai City(Grant No.19ZR1473700)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01).
文摘Patterns resulted from modulation instability are ubiquitous and have been extensively studied in optics and Bose-Einstein condensates. However, these patterns have not been realized in ultracold Fermi gases, although there has been considerable theoretical interest in this field. Here we report an experimental observation of space-time patterns in a superfluid Fermi gas excited by red-detuned laser light. Longitudinal spatially fluctuated laser beams induce the spontaneous formation of two different kinds of patterns. For strongly interacting Fermi gas, the induced patterns accompanied by phonon excitations demonstrate a striking"X"-type dispersion relation between frequency and wavevector. Then, the propagation of such patterns in the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer crossover is investigated, which is related to the speed of sound and agrees well with theoretical calculations. The observed patterns in noninteracting Fermi gases are stationary without phonon excitations and show a much longer lifetime.
基金H.C.is supported by the National Natural Science Foundation of China under project number 11774236the Ministry of Science and Technology of China under project number SQ2020YFE010418+3 种基金Open Grant of State Key Laboratory of Low Dimensional Quantum Physics at Tsinghua UniversityG.L.is supported by NSF of China(Grant No.11874263)the Sino-German mobility program(M-0006)Shanghai Technology Innovation Action Plan 2020-Integrated Circuit Technology Support Program(Project No.20DZ1100605).
文摘Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.
