We construct a new bipartite entangled state（NBES）,which describes both the squeezing and the entanglement involved in the parametric down-conversion process and can be produced using a symmetric beam splitter.Const...We construct a new bipartite entangled state（NBES）,which describes both the squeezing and the entanglement involved in the parametric down-conversion process and can be produced using a symmetric beam splitter.Constructing asymmetric ket-bra integrations based on the NBES leads to some new squeezing operators,which clearly exhibit the relationships between squeezing and entangled state transformations.Moreover,an entangled Wigner operator with a definite physical meaning is also presented.展开更多
The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whos...The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whose constant （and so its frequency） depends on the quantum states ofanother system. Recently, it is realized that by the assumption of frequency modulation of ω to ω √1＋ μα＋α the mentioned idea can be established. In the present paper, we generalize the approach of quantum optical spring with particular attention to the dependence or trequency to the intensity of radiation field that naturally observes in the nonlinear coherent states, from which we arrive at a physical system has been called by us as nonlinear quantum optical spring. Then, after the introduction of the generalized tlamiltonian of nonlinear quantum optical spring and it＇s solution, we will investigate the nonclassical properties of the obtained states. Specially, typical collapse and revival in the distribution functions and squeezing parameters, as particular quantum features, will be revealed.展开更多
By introducing the entangled Fresnel operator （EFO） this paper demonstrates that there exists ABCD theorem for two-mode entangled case in quantum optics. The canonical operator method as mapping of ray-transfer ABCD...By introducing the entangled Fresnel operator （EFO） this paper demonstrates that there exists ABCD theorem for two-mode entangled case in quantum optics. The canonical operator method as mapping of ray-transfer ABCD matrix is explicitly shown by EFO＇s normally ordered expansion through the coherent state representation and the technique of integration within an ordered product of operators.展开更多
We investigate the sensitivity of phase estimation in a Mach-Zehnder interferometer with photon-subtracted twomode squeezed vacuum states.Our results show that, for given initial squeezing parameter, both symmetric an...We investigate the sensitivity of phase estimation in a Mach-Zehnder interferometer with photon-subtracted twomode squeezed vacuum states.Our results show that, for given initial squeezing parameter, both symmetric and asymmetric photon subtractions can further improve the quantum Cramér-Rao bound(i.e., the ultimate phase sensitivity), especially for single-mode photon subtraction.On the other hand, the quantum Cramér-Rao bound can be reached by parity detection for symmetric photon-subtracted two-mode squeezed vacuum states at particular values of the phase shift, but it is not valid for asymmetric photon-subtracted two-mode squeezed vacuum states.In addition, compared with the two-mode squeezed vacuum state, the phase sensitivity via parity detection with asymmetric photon-subtracted two-mode squeezed vacuum states will be getting worse.Thus, parity detection may not always be the optimal detection scheme for nonclassical states of light when they are considered as the interferometer states.展开更多
We let a set of beam splitters of vacuum mode with a chosen transmittance parameter η in interaction with a separable coherent states.This model induces the production of an attenuated quantum channels based on entan...We let a set of beam splitters of vacuum mode with a chosen transmittance parameter η in interaction with a separable coherent states.This model induces the production of an attenuated quantum channels based on entangled optical states.Indeed,the decoherence effect is exploited positively here to generate such kind of quantum channels.Next,the amplitude damping and the entanglement amount of these produced channels are enhanced thereafter by a probabilistic quasi amplification process using again a 50 : 50 beam splitter.展开更多
Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. The...Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. Then the relative photon-number densities of the transmitted field, the reflected field and the absorbed field are gotten through the correlation functions. Furthermore, the contributions of the relative permittivity and permeability of the metamaterials to the transmission are analyzed. Our results show that the permittivity and permeability reinforce the transmission for frequencies that are big compared with the magnetic resonance frequency.展开更多
Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ...Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ofthese two types of schemes by considering that they can be classified into nine possible level styles as the second-ordersub-schemes using laser fields.Further we point out the complexity of their more than one hundred realistic configurationsas the third-order four-level sub-schemes that may appear in the optical quantum coherence experiments.Throughoutthis paper we review which configurations have been studied in some research aspects and which ones not,accordingto our knowledge,in order to be propitious to next steps of theoretical and experimental investigations,especially forapplications in the fields of quantum optics,quantum information science,laser spectroscopy,and so on.展开更多
Entangled optical quantum states are essential towards solving questions in fundamental physics and are at the heart of applications in quantum information science. For advancing the research and development of quantu...Entangled optical quantum states are essential towards solving questions in fundamental physics and are at the heart of applications in quantum information science. For advancing the research and development of quantum technologies, practical access to the generation and manipulation of photon states carrying significant quantum resources is required. Recently, integrated photonics has become a leading platform for the compact and cost- efficient generation and processing of optical quantum states. Despite significant advances, most on-chip non- classical light sources are still limited to basic bi-photon systems formed by two-dimensional states （i.e., qubits）. An interesting approach beating large potential is the use of the time or frequency domain to enabled the scalable on- chip generation of complex states. In this manuscript, we review recent efforts in using on-chip optical frequency combs for quantum state generation and telecommunica- tions components for their coherent control. In particular, the generation of bi- and multi-photon entangled qubit states has been demonstrated, based on a discrete time domain approach. Moreover, the on-chip generation of high-dimensional entangled states （quDits） has recentlybeen realized, wherein the photons are created in a coherent superposition of multiple pure frequency modes. The time- and frequency-domain states formed with on-chip frequency comb sources were coherently manipulated via off-the-shelf telecommunications compo- nents. Our results suggest that microcavity-based entangled photon states and their coherent control using accessible telecommunication infrastructures can open up new venues for scalable quantum information science.展开更多
The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes ...The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes used there are incapable of cloning quantum entangled states in multipartite systems.Few schemes were proposed for cloning multiparticle states,which consume more entanglement resources with loss of qubits,and the fidelity of the cloned state is relatively low.In this paper,cloning schemes for bipartite and tripartite entangled states based on photonic quantum walk and entanglement swapping are proposed.The results show that according to the proposed schemes,two high-fidelity(up to 0.75)cloned states can be obtained with less quantum resource consumption.Because of the simple cloning steps,few quantum resources and high fidelity,these schemes are both efficient and feasible.Moreover,this cloning machine eliminates the need for tracing out cloning machine,thereby minimizing resource waste.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
In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the fi...In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method(FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation(SHG) and third-harmonic generation(THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.展开更多
Dispersive optics quantum key distribution(DO-QKD)based on energy-time entangled photon pairs is an important QKD scheme.In DO-QKD,the arrival time of photons is used in key generation and security analysis,which woul...Dispersive optics quantum key distribution(DO-QKD)based on energy-time entangled photon pairs is an important QKD scheme.In DO-QKD,the arrival time of photons is used in key generation and security analysis,which would be greatly affected by fiber dispersion.In this work,we establish a theoretical model of the entanglement-based DO-QKD system,considering the protocol,physical processes(such as fiber transmission and single-photon detection),and the analysis of security tests.Based on this theoretical model,we investigate the influence of chromatic dispersion introduced by transmission fibers on the performance of DO-QKD.By analyzing the benefits and costs of dispersion compensation,the system performance under G.652 and G.655 optical fibers are shown,respectively.The results show that dispersion compensation is unnecessary for DO-QKD systems in campus networks and even metro networks.Whereas,it is still required in DO-QKD systems with longer fiber transmission distances.展开更多
It has recently been shown that linear optics alone would suffice to implement efficient quantum computation. Quantum computation circuits using coherent states as the logical qubits can be constructed from very simpl...It has recently been shown that linear optics alone would suffice to implement efficient quantum computation. Quantum computation circuits using coherent states as the logical qubits can be constructed from very simple linear networks, conditional measurements and coherent superposition resource states. We present the quantum game under quantum noise and a proposal for implementing the noisy quantum game using only linear optics.展开更多
This paper presents a scheme for faithfully distributing a pure entanglement between two parties over an arbitrary collective-noise channel with linear optics. The transmission is assisted by an additional qubit again...This paper presents a scheme for faithfully distributing a pure entanglement between two parties over an arbitrary collective-noise channel with linear optics. The transmission is assisted by an additional qubit against collective noise. The receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the resource used to get a pure entanglement state is finite, and so is easier to establish entanglement in practice than quantum entanglement purification.展开更多
We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contribution...We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contributions from various optical-phonon modes to the ground state energy as functions of the well width and Mg composition. In our calculations, we considered the effects of confined optical phonon modes, interface-optical phonon modes, and half-space phonon modes, as well as the anisotropy of the electron effective band mass, phonon frequency, and dielectric constant. Our numerical results indicate that the electron–optical phonon interactions importantly affect the polaronic energies in the ZnO/MgxZn1-xO quantum well. The electron–optical phonon interactions decrease the polaron energies. For quantum wells with narrower wells, the interface optical phonon and half-space phonon modes contribute more to the polaronic energies than the confined phonon modes. However, for wider quantum wells, the total contribution to the polaronic energy mainly comes from the confined modes. The contributions of the various phonon modes to the transition energy change differently with increasing well width. The contribution of the half-space phonons decreases slowly as the QW width increases, whereas the contributions of the confined and interface phonons reach a maximum at d ≈ 5.0 nm and then decrease slowly. However,the total contribution of phonon modes to the transition energy is negative and increases gradually with the QW width of d.As the composition x increases, the total contribution of phonons to the ground state energies increases slowly, but the total contributions of phonons to the transition energies decrease gradually. We analyze the physical reasons for these behaviors in detail.展开更多
The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of t...The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn1-xCdxSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field.展开更多
By employing displacement operations, single-photon subtractions, and weak cross-Kerr nonlinearity, we propose an alternative way of implementing several universal quantum logical gates for all-optical hybrid qubits e...By employing displacement operations, single-photon subtractions, and weak cross-Kerr nonlinearity, we propose an alternative way of implementing several universal quantum logical gates for all-optical hybrid qubits encoded in both single-photon polarization state and coherent state. Since these schemes can be straightforwardly implemented only using local operations without teleportation procedure, therefore, less physical resources and simpler operations are required than the existing schemes. With the help of displacement operations, a large phase shift of the coherent state can be obtained via currently available tiny cross-Kerr nonlinearity. Thus, all of these schemes are nearly deterministic and feasible under current technology conditions, which makes them suitable for large-scale quantum computing.展开更多
CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD),...CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD), and ultra violet-visible (UV-Vis) spectrophotometer. The results show that high-quality cubic CdSe QDs were obtained. It is also obtained that temperature is one of the most important factors the affect on the particle size and optical properties of the prepared QDs samples.展开更多
In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator （EOM） used for generating ...In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator （EOM） used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.展开更多
In this paper,we briefly review the recent experimental progresses in quantum optics based on four-wave mixing(FWM) processes in hot rubidium vapor,particularly our two recent experiments in quantum information.We hav...In this paper,we briefly review the recent experimental progresses in quantum optics based on four-wave mixing(FWM) processes in hot rubidium vapor,particularly our two recent experiments in quantum information.We have experimentally produced strong quantum correlations between three bright beams generated by two cascaded FWM processes.The intensity difference squeezing with the cascaded system is enhanced to(-7.0±0.1)d B from the(-5.5±0.1)d B/(4.5±0.1)d B with only one FWM process.Also,this system can be easily extended to multiple modes using multiple FWM processes.Besides,we have also successfully realized a cascade all-optical transistor(AOT),which is driven by a very weak light beam about 800 photons in total.The required probe power for achieving a switching efficiency of 50% can be as low as 180 p W,and it can manipulate a light beam with power of 5.0×106 times more,which proves the cascade of the AOT.Both experiments may find wide applications in quantum information and optical communication.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 11147009)the Natural Science Foundation of Shandong Province,China (Grant Nos. ZR2010AQ027 and ZR2012AM004)the Shandong Provincial Higher Educational Science and Technology Program,China (Grant No. J10LA15)
文摘We construct a new bipartite entangled state（NBES）,which describes both the squeezing and the entanglement involved in the parametric down-conversion process and can be produced using a symmetric beam splitter.Constructing asymmetric ket-bra integrations based on the NBES leads to some new squeezing operators,which clearly exhibit the relationships between squeezing and entangled state transformations.Moreover,an entangled Wigner operator with a definite physical meaning is also presented.
文摘The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whose constant （and so its frequency） depends on the quantum states ofanother system. Recently, it is realized that by the assumption of frequency modulation of ω to ω √1＋ μα＋α the mentioned idea can be established. In the present paper, we generalize the approach of quantum optical spring with particular attention to the dependence or trequency to the intensity of radiation field that naturally observes in the nonlinear coherent states, from which we arrive at a physical system has been called by us as nonlinear quantum optical spring. Then, after the introduction of the generalized tlamiltonian of nonlinear quantum optical spring and it＇s solution, we will investigate the nonclassical properties of the obtained states. Specially, typical collapse and revival in the distribution functions and squeezing parameters, as particular quantum features, will be revealed.
基金supported by the National Natural Science Foundation of China (Grant Nos 10775097 and 10475056)
文摘By introducing the entangled Fresnel operator （EFO） this paper demonstrates that there exists ABCD theorem for two-mode entangled case in quantum optics. The canonical operator method as mapping of ray-transfer ABCD matrix is explicitly shown by EFO＇s normally ordered expansion through the coherent state representation and the technique of integration within an ordered product of operators.
基金Project supported by the National Natural Science Foundation of China(Grant No.11404040)the Qing Lan Project of the Higher Educations of Jiangsu Province of China
文摘We investigate the sensitivity of phase estimation in a Mach-Zehnder interferometer with photon-subtracted twomode squeezed vacuum states.Our results show that, for given initial squeezing parameter, both symmetric and asymmetric photon subtractions can further improve the quantum Cramér-Rao bound(i.e., the ultimate phase sensitivity), especially for single-mode photon subtraction.On the other hand, the quantum Cramér-Rao bound can be reached by parity detection for symmetric photon-subtracted two-mode squeezed vacuum states at particular values of the phase shift, but it is not valid for asymmetric photon-subtracted two-mode squeezed vacuum states.In addition, compared with the two-mode squeezed vacuum state, the phase sensitivity via parity detection with asymmetric photon-subtracted two-mode squeezed vacuum states will be getting worse.Thus, parity detection may not always be the optimal detection scheme for nonclassical states of light when they are considered as the interferometer states.
文摘We let a set of beam splitters of vacuum mode with a chosen transmittance parameter η in interaction with a separable coherent states.This model induces the production of an attenuated quantum channels based on entangled optical states.Indeed,the decoherence effect is exploited positively here to generate such kind of quantum channels.Next,the amplitude damping and the entanglement amount of these produced channels are enhanced thereafter by a probabilistic quasi amplification process using again a 50 : 50 beam splitter.
文摘Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. Then the relative photon-number densities of the transmitted field, the reflected field and the absorbed field are gotten through the correlation functions. Furthermore, the contributions of the relative permittivity and permeability of the metamaterials to the transmission are analyzed. Our results show that the permittivity and permeability reinforce the transmission for frequencies that are big compared with the magnetic resonance frequency.
基金Supported by the Research Starting Funds of Tianjin Polytechnic University under Grant Nos.20080033 and 20070010
文摘Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ofthese two types of schemes by considering that they can be classified into nine possible level styles as the second-ordersub-schemes using laser fields.Further we point out the complexity of their more than one hundred realistic configurationsas the third-order four-level sub-schemes that may appear in the optical quantum coherence experiments.Throughoutthis paper we review which configurations have been studied in some research aspects and which ones not,accordingto our knowledge,in order to be propitious to next steps of theoretical and experimental investigations,especially forapplications in the fields of quantum optics,quantum information science,laser spectroscopy,and so on.
文摘Entangled optical quantum states are essential towards solving questions in fundamental physics and are at the heart of applications in quantum information science. For advancing the research and development of quantum technologies, practical access to the generation and manipulation of photon states carrying significant quantum resources is required. Recently, integrated photonics has become a leading platform for the compact and cost- efficient generation and processing of optical quantum states. Despite significant advances, most on-chip non- classical light sources are still limited to basic bi-photon systems formed by two-dimensional states （i.e., qubits）. An interesting approach beating large potential is the use of the time or frequency domain to enabled the scalable on- chip generation of complex states. In this manuscript, we review recent efforts in using on-chip optical frequency combs for quantum state generation and telecommunica- tions components for their coherent control. In particular, the generation of bi- and multi-photon entangled qubit states has been demonstrated, based on a discrete time domain approach. Moreover, the on-chip generation of high-dimensional entangled states （quDits） has recentlybeen realized, wherein the photons are created in a coherent superposition of multiple pure frequency modes. The time- and frequency-domain states formed with on-chip frequency comb sources were coherently manipulated via off-the-shelf telecommunications compo- nents. Our results suggest that microcavity-based entangled photon states and their coherent control using accessible telecommunication infrastructures can open up new venues for scalable quantum information science.
文摘The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes used there are incapable of cloning quantum entangled states in multipartite systems.Few schemes were proposed for cloning multiparticle states,which consume more entanglement resources with loss of qubits,and the fidelity of the cloned state is relatively low.In this paper,cloning schemes for bipartite and tripartite entangled states based on photonic quantum walk and entanglement swapping are proposed.The results show that according to the proposed schemes,two high-fidelity(up to 0.75)cloned states can be obtained with less quantum resource consumption.Because of the simple cloning steps,few quantum resources and high fidelity,these schemes are both efficient and feasible.Moreover,this cloning machine eliminates the need for tracing out cloning machine,thereby minimizing resource waste.
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.
文摘In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method(FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation(SHG) and third-harmonic generation(THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.
基金the National Key R&D Program of China under Grants No.2017YFA0303704 and No.2018YFB2200400Natural Science Foundation of Beijing under Grant No.Z180012National Natural Science Foundation of China under Grants No.61875101 and No.91750206.
文摘Dispersive optics quantum key distribution(DO-QKD)based on energy-time entangled photon pairs is an important QKD scheme.In DO-QKD,the arrival time of photons is used in key generation and security analysis,which would be greatly affected by fiber dispersion.In this work,we establish a theoretical model of the entanglement-based DO-QKD system,considering the protocol,physical processes(such as fiber transmission and single-photon detection),and the analysis of security tests.Based on this theoretical model,we investigate the influence of chromatic dispersion introduced by transmission fibers on the performance of DO-QKD.By analyzing the benefits and costs of dispersion compensation,the system performance under G.652 and G.655 optical fibers are shown,respectively.The results show that dispersion compensation is unnecessary for DO-QKD systems in campus networks and even metro networks.Whereas,it is still required in DO-QKD systems with longer fiber transmission distances.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘It has recently been shown that linear optics alone would suffice to implement efficient quantum computation. Quantum computation circuits using coherent states as the logical qubits can be constructed from very simple linear networks, conditional measurements and coherent superposition resource states. We present the quantum game under quantum noise and a proposal for implementing the noisy quantum game using only linear optics.
基金supported by the National Natural Science Foundation of China (Grant No 10604008)Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No 200723)Beijing Natural Science Foundation (Grant No 1082008)
文摘This paper presents a scheme for faithfully distributing a pure entanglement between two parties over an arbitrary collective-noise channel with linear optics. The transmission is assisted by an additional qubit against collective noise. The receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the resource used to get a pure entanglement state is finite, and so is easier to establish entanglement in practice than quantum entanglement purification.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11264027 and 11364030)the Project of Prairie Excellent Specialist of Inner Mongolia,Chinathe "Thousand,Hundred and Ten" Talent Training Project Foundation of Inner Mongolia Normal University,China(Grant No.RCPY-2-2012-K-039)
文摘We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contributions from various optical-phonon modes to the ground state energy as functions of the well width and Mg composition. In our calculations, we considered the effects of confined optical phonon modes, interface-optical phonon modes, and half-space phonon modes, as well as the anisotropy of the electron effective band mass, phonon frequency, and dielectric constant. Our numerical results indicate that the electron–optical phonon interactions importantly affect the polaronic energies in the ZnO/MgxZn1-xO quantum well. The electron–optical phonon interactions decrease the polaron energies. For quantum wells with narrower wells, the interface optical phonon and half-space phonon modes contribute more to the polaronic energies than the confined phonon modes. However, for wider quantum wells, the total contribution to the polaronic energy mainly comes from the confined modes. The contributions of the various phonon modes to the transition energy change differently with increasing well width. The contribution of the half-space phonons decreases slowly as the QW width increases, whereas the contributions of the confined and interface phonons reach a maximum at d ≈ 5.0 nm and then decrease slowly. However,the total contribution of phonon modes to the transition energy is negative and increases gradually with the QW width of d.As the composition x increases, the total contribution of phonons to the ground state energies increases slowly, but the total contributions of phonons to the transition energies decrease gradually. We analyze the physical reasons for these behaviors in detail.
基金supported by the National Natural Science Foundation of China(Grant No.11364028)the Major Projects of the Natural Science Foundation of Inner Mongolia Autonomous Region,China(Grant No.2013ZD02)the Project of "Prairie Excellent" Engineering in Inner Mongolia Autonomous Region,China
文摘The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn1-xCdxSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61465013,11465020,and 11264042)
文摘By employing displacement operations, single-photon subtractions, and weak cross-Kerr nonlinearity, we propose an alternative way of implementing several universal quantum logical gates for all-optical hybrid qubits encoded in both single-photon polarization state and coherent state. Since these schemes can be straightforwardly implemented only using local operations without teleportation procedure, therefore, less physical resources and simpler operations are required than the existing schemes. With the help of displacement operations, a large phase shift of the coherent state can be obtained via currently available tiny cross-Kerr nonlinearity. Thus, all of these schemes are nearly deterministic and feasible under current technology conditions, which makes them suitable for large-scale quantum computing.
文摘CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD), and ultra violet-visible (UV-Vis) spectrophotometer. The results show that high-quality cubic CdSe QDs were obtained. It is also obtained that temperature is one of the most important factors the affect on the particle size and optical properties of the prepared QDs samples.
基金Project supported by the National Natural Science Foundation of China(Grant No.61108039)the Major Research Plan of the National Natural Science Foundation of China(Grant No.91121023)the Scientific Research Foundation of Graduate School of South China Normal University(Grant No.2012kyjj224)
文摘In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator （EOM） used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.
基金supported by the National Natural Science Foundation of China(Grants Nos.91436211,11374104,10974057 and 11234003)the Specialized Research Fund for the Doctoral Program(Grant No.20130076110011)+4 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Program for New Century Excellent Talents in University(Grant No.NCET-10-0383)the Shu Guang project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation(Grant No.11SG26)the Shanghai Pujiang Program(Grant No.09PJ1404400)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry and the National Basic Research Program of China(Grant No.2011CB921604)
文摘In this paper,we briefly review the recent experimental progresses in quantum optics based on four-wave mixing(FWM) processes in hot rubidium vapor,particularly our two recent experiments in quantum information.We have experimentally produced strong quantum correlations between three bright beams generated by two cascaded FWM processes.The intensity difference squeezing with the cascaded system is enhanced to(-7.0±0.1)d B from the(-5.5±0.1)d B/(4.5±0.1)d B with only one FWM process.Also,this system can be easily extended to multiple modes using multiple FWM processes.Besides,we have also successfully realized a cascade all-optical transistor(AOT),which is driven by a very weak light beam about 800 photons in total.The required probe power for achieving a switching efficiency of 50% can be as low as 180 p W,and it can manipulate a light beam with power of 5.0×106 times more,which proves the cascade of the AOT.Both experiments may find wide applications in quantum information and optical communication.
