Based on the coherent interaction and action–counteraction principles,we investigate the ground state properties for small polaron systems,the coherent-squeezed fluctuation correction,and the anomalous lattice quantu...Based on the coherent interaction and action–counteraction principles,we investigate the ground state properties for small polaron systems,the coherent-squeezed fluctuation correction,and the anomalous lattice quantum fluctuation,with the new variational generator containing correlated squeezed-coherent coupling and quantum entanglement.Noting tha t-2t is the T.B.A.energy,for the coherent interaction effect,we find the ground-state energy E_(0)to be-2.428t,in which the coherent squeezed fluctuation correction-A_(0)t is-0.463t(where t is the hopping integral,ωis the phonon frequency),with the electron–one-phonon coupling constant g=1 and the electron–two-phonon coupling constant g_(1)=-0.1.However,as a result of the action–counteraction effect,E_(0)is-2.788t,but-E_(0)t is-0.735t.As to the polaron binding energy(EP),for the coherent interaction effect,E_(P) is-1.38ω,but for the action–counteraction effect,E_(P) is-1.88ω.In particular,the electron–two-phonon interaction noticeably enlarges the coherent interaction and the coherent squeezed quantum fluctuation correction.By intervening with the quantum entanglement,the evolutions of the squeezed coherent state and the lattice quantum fluctuation begin to take control.At that time,we encounter a new quantum phase coherence phenomenon—the collapse and revival of inversion repeatedly for the coherent state in the entangled evolution.展开更多
The existence of one-dimensional bright Kerr solitons is investigated in Kerr media beyond the paraxial approximation. It is found that a nonparaxial soliton with no less than a minimum dimensionless width of about 0....The existence of one-dimensional bright Kerr solitons is investigated in Kerr media beyond the paraxial approximation. It is found that a nonparaxial soliton with no less than a minimum dimensionless width of about 0.76 can exist, which corresponds to the real width about a wavelength. Besides, the coherent interactions between two nonparaxial bright solitons in Kerr media are also investigated in detail. It is found that their separation and intensity ratio have great influence on the coherent interaction between these two solitons. Furthermore, the effect of the relative phase difference on the nonparaxial interaction is quite different from that on the paraxial interaction. Periodical breath, merging, repulsion, and energy transferring can be realized separately by choosing an appropriate initial relative phase between the coherent solitons.展开更多
The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an ...The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.展开更多
We theoretically and numerically investigate the coherence of disordered bosonic gas with effective two- and three-body interactions within a two-site Bose-Hubbard model. By properly adjusting the two- and three-body ...We theoretically and numerically investigate the coherence of disordered bosonic gas with effective two- and three-body interactions within a two-site Bose-Hubbard model. By properly adjusting the two- and three-body interactions and the disorder, the coherence of the system exhibits new and interesting phenomena, including the resonance character of coherence against the disorder in the purely two- or three-body interactions system. More interestingly, the disorder and three-body interactions together can suppress the coherence of the purely three-body interactions system, which is different from the case in which the disorder and two-body interactions together can enhance the coherence in certain values of two.body interaction. Furthermore, when two- or three- body interactions are attractive or repulsive, the phase coherence exhibits completely different phenomena. In particular, if two- or three-body interactions are attractive, the coherence of the system can be significantly enhanced in certain regions. Correspondingly, the phase coherence of the system is strongly related to the effective interaction energy. The results provide a possible way for studying the coherence of bosonic gas with multi-atoms＇ interactions in the presence of the disorder.展开更多
We have studied the phenomenon of electromagnetically induced transparency（EIT） of ^87Rb vapor with a buffer gas in a magnetic field at room temperature. It is found that the spectral lines caused by the velocity se...We have studied the phenomenon of electromagnetically induced transparency（EIT） of ^87Rb vapor with a buffer gas in a magnetic field at room temperature. It is found that the spectral lines caused by the velocity selective optical pump effects get much weaker and wider when the sample cell is mixed with a 5-Torr N_2 gas while the EIT signal is kept almost unchanged. A weighted least-square fit is also developed to remove the Doppler broadening completely. This spectral method provides a way to measure the Zeeman splitting with high resolution, for example, the Λ-type EIT resonance splits into four peaks on the D_2 line of ^87Rb in the thermal 2-cm vapor cell with a magnetic field along the electric field of the linearly polarized coupling laser. The high-resolution spectrum can be used to lock the laser to a given frequency by tuning the magnetic field.展开更多
We experimentally demonstrate the nonlinear interaction between two chirped broadband single-photon-level coherent states. Each chirped coherent state is generated in independent fiber Bragg gratings. They are simulta...We experimentally demonstrate the nonlinear interaction between two chirped broadband single-photon-level coherent states. Each chirped coherent state is generated in independent fiber Bragg gratings. They are simultaneously coupled into a high-efficiency nonlinear waveguide, where they are converted into a narrowband singlephoton state with a new frequency by the process of sum-frequency generation(SFG). A higher SFG efficiency of1.06 × 10-7is realized, and this efficiency may achieve heralding entanglement at a distance. This also made it possible to realize long-distance quantum communication, such as device-independent quantum key distribution,by directly using broadband single photons without filtering.展开更多
There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduce...There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduced hacking as the transmission phenomenon. In this article, an SPP-based reduced hacking scheme is presented at interface between atomic medium and metallic conductor. The SPP propagation is manipulated with conductivity of the metal. The delay or advance of the SPP is found to create nanosecond time gap which can be used for storing and sending the information safely. The reduced hacking is further modified with conductivity of the metal and the control parameters of the atomic medium.展开更多
The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman...The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.展开更多
A scheme of an optical quantum Fredkin gate is presented based on weak cross-Kerr nonlinearity. By an auxiliary coherent state with the cross-Kerr nonlinearity effect, photons can interact with each other indirectly, ...A scheme of an optical quantum Fredkin gate is presented based on weak cross-Kerr nonlinearity. By an auxiliary coherent state with the cross-Kerr nonlinearity effect, photons can interact with each other indirectly, and a non-demolition measurement for photons can be implemented. Combined with the homodyne detection, classical feedforward, polarization beam splitters and Pauli-X operations, a controlled-path gate is constructed. Furthermore, a quantum Fredkin gate is built based on the controlled-path gate. The proposed Fredkin gate is simple in structure and feasible by current experimental technology.展开更多
Terahertz(THz) generation by periodically-poled RbTiOPO_4(PPRTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation(DFG) processes is theoretically analyzed. The cascaded Stokes and a...Terahertz(THz) generation by periodically-poled RbTiOPO_4(PPRTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation(DFG) processes is theoretically analyzed. The cascaded Stokes and anti-Stokes interaction processes are investigated from coupled wave equations. The THz intensities and quantum conversion efficiency are calculated. Compared with that of non-cascaded DFG processes, the THz intensity in 7-order cascaded DFG processes is increased to 2.95 times. The quantum conversion efficiency of 149.9% in cascaded processes can be realized, which exceeds the Manley-Rowe limit.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.10574163)。
文摘Based on the coherent interaction and action–counteraction principles,we investigate the ground state properties for small polaron systems,the coherent-squeezed fluctuation correction,and the anomalous lattice quantum fluctuation,with the new variational generator containing correlated squeezed-coherent coupling and quantum entanglement.Noting tha t-2t is the T.B.A.energy,for the coherent interaction effect,we find the ground-state energy E_(0)to be-2.428t,in which the coherent squeezed fluctuation correction-A_(0)t is-0.463t(where t is the hopping integral,ωis the phonon frequency),with the electron–one-phonon coupling constant g=1 and the electron–two-phonon coupling constant g_(1)=-0.1.However,as a result of the action–counteraction effect,E_(0)is-2.788t,but-E_(0)t is-0.735t.As to the polaron binding energy(EP),for the coherent interaction effect,E_(P) is-1.38ω,but for the action–counteraction effect,E_(P) is-1.88ω.In particular,the electron–two-phonon interaction noticeably enlarges the coherent interaction and the coherent squeezed quantum fluctuation correction.By intervening with the quantum entanglement,the evolutions of the squeezed coherent state and the lattice quantum fluctuation begin to take control.At that time,we encounter a new quantum phase coherence phenomenon—the collapse and revival of inversion repeatedly for the coherent state in the entangled evolution.
基金Project supported by the Dongguan Science and Technology Program,Guangdong Province,China(Grant No.200910814038)
文摘The existence of one-dimensional bright Kerr solitons is investigated in Kerr media beyond the paraxial approximation. It is found that a nonparaxial soliton with no less than a minimum dimensionless width of about 0.76 can exist, which corresponds to the real width about a wavelength. Besides, the coherent interactions between two nonparaxial bright solitons in Kerr media are also investigated in detail. It is found that their separation and intensity ratio have great influence on the coherent interaction between these two solitons. Furthermore, the effect of the relative phase difference on the nonparaxial interaction is quite different from that on the paraxial interaction. Periodical breath, merging, repulsion, and energy transferring can be realized separately by choosing an appropriate initial relative phase between the coherent solitons.
基金Project supported by the National Natural Science Foundation of China(Grant No.11874011)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology.
文摘The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11475027,11274255 and 11305132the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grand No 20136203110001+1 种基金the Natural Science Foundation of Gansu Province under Grant No 1506RJYA131the Creation of Science and Technology of Northwest Normal University under Grant Nos NWNU-KJCXGC-03-48 and NWNU-LKQN-12-12
文摘We theoretically and numerically investigate the coherence of disordered bosonic gas with effective two- and three-body interactions within a two-site Bose-Hubbard model. By properly adjusting the two- and three-body interactions and the disorder, the coherence of the system exhibits new and interesting phenomena, including the resonance character of coherence against the disorder in the purely two- or three-body interactions system. More interestingly, the disorder and three-body interactions together can suppress the coherence of the purely three-body interactions system, which is different from the case in which the disorder and two-body interactions together can enhance the coherence in certain values of two.body interaction. Furthermore, when two- or three- body interactions are attractive or repulsive, the phase coherence exhibits completely different phenomena. In particular, if two- or three-body interactions are attractive, the coherence of the system can be significantly enhanced in certain regions. Correspondingly, the phase coherence of the system is strongly related to the effective interaction energy. The results provide a possible way for studying the coherence of bosonic gas with multi-atoms＇ interactions in the presence of the disorder.
基金Project supported by the National Key Basic Research Program of China(Grant No.2013CB922003)the National Natural Science Foundation of China(Grant Nos.91421305,91121005,11674359,and 91436106)
文摘We have studied the phenomenon of electromagnetically induced transparency（EIT） of ^87Rb vapor with a buffer gas in a magnetic field at room temperature. It is found that the spectral lines caused by the velocity selective optical pump effects get much weaker and wider when the sample cell is mixed with a 5-Torr N_2 gas while the EIT signal is kept almost unchanged. A weighted least-square fit is also developed to remove the Doppler broadening completely. This spectral method provides a way to measure the Zeeman splitting with high resolution, for example, the Λ-type EIT resonance splits into four peaks on the D_2 line of ^87Rb in the thermal 2-cm vapor cell with a magnetic field along the electric field of the linearly polarized coupling laser. The high-resolution spectrum can be used to lock the laser to a given frequency by tuning the magnetic field.
基金National Natural Science Foundation of China(NSFC)(11564018,61125503,61235009)Foundation for Development of Science and Technology of Shanghai(13JC1408300)
文摘We experimentally demonstrate the nonlinear interaction between two chirped broadband single-photon-level coherent states. Each chirped coherent state is generated in independent fiber Bragg gratings. They are simultaneously coupled into a high-efficiency nonlinear waveguide, where they are converted into a narrowband singlephoton state with a new frequency by the process of sum-frequency generation(SFG). A higher SFG efficiency of1.06 × 10-7is realized, and this efficiency may achieve heralding entanglement at a distance. This also made it possible to realize long-distance quantum communication, such as device-independent quantum key distribution,by directly using broadband single photons without filtering.
文摘There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduced hacking as the transmission phenomenon. In this article, an SPP-based reduced hacking scheme is presented at interface between atomic medium and metallic conductor. The SPP propagation is manipulated with conductivity of the metal. The delay or advance of the SPP is found to create nanosecond time gap which can be used for storing and sending the information safely. The reduced hacking is further modified with conductivity of the metal and the control parameters of the atomic medium.
基金Project supported by the National Natural Science Foundation of China(Grant No.61008016)the Natural Science Foundation in Shaanxi Province,China(Grant No.2010JQ1002)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20106101120020)
文摘The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.
基金supported by the National Natural Science Foundation of China(Nos.61372076 and 61301171)the Programme of Introducing Talents of Discipline to Universities(No.B08038)
文摘A scheme of an optical quantum Fredkin gate is presented based on weak cross-Kerr nonlinearity. By an auxiliary coherent state with the cross-Kerr nonlinearity effect, photons can interact with each other indirectly, and a non-demolition measurement for photons can be implemented. Combined with the homodyne detection, classical feedforward, polarization beam splitters and Pauli-X operations, a controlled-path gate is constructed. Furthermore, a quantum Fredkin gate is built based on the controlled-path gate. The proposed Fredkin gate is simple in structure and feasible by current experimental technology.
基金supported by the National Natural Science Foundation of China(Nos.61201101,61601183 and 61205003)the Young Backbone Teachers in University of Henan Province(No.2014GGJS-065)+1 种基金the Foundation and Advanced Technology Research Program of Henan Province(No.162300410269)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province(No.16IRTSTHN017)
文摘Terahertz(THz) generation by periodically-poled RbTiOPO_4(PPRTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation(DFG) processes is theoretically analyzed. The cascaded Stokes and anti-Stokes interaction processes are investigated from coupled wave equations. The THz intensities and quantum conversion efficiency are calculated. Compared with that of non-cascaded DFG processes, the THz intensity in 7-order cascaded DFG processes is increased to 2.95 times. The quantum conversion efficiency of 149.9% in cascaded processes can be realized, which exceeds the Manley-Rowe limit.
