We theoretically study the collective decay of two atoms trapped in a single mode cavity and we describe the evolution of the population of Dicke states. We show that the collective decay property is strongly dependen...We theoretically study the collective decay of two atoms trapped in a single mode cavity and we describe the evolution of the population of Dicke states. We show that the collective decay property is strongly dependent on the phase of atomic radiation and the speeding up of collective decay can only be observed in a bad cavity regime. For in-or out-phase case,this occurs due to the quantum interference enhancement, no matter which atom is excited initially. For π/2 phase, the speeding up of collective decay takes place if the first atom is excited at the beginning. However, it disappears due to the quantum interference cancellation if the second atom is excited. Compared with the in-phase and out-phase cases,we also show that the speeding up of collective decay can be significantly enhanced in strong coupling regime for π/2 phase, although one atom is decoupled to the cavity in this condition. The study presented here is helpful to understand the physical mechanism of collective decay in cavity quantum electrodynamics and it provides a useful method to control the collective decay phenomenon via quantum interference effect.展开更多
This paper presents a scheme for implementing a Fredkin gate on three modes of a cavity. The scheme is based on the dispersive atom-cavity interaction. By modulating the cavity frequency and the atomic transition freq...This paper presents a scheme for implementing a Fredkin gate on three modes of a cavity. The scheme is based on the dispersive atom-cavity interaction. By modulating the cavity frequency and the atomic transition frequency appropriately, it obtains the effective form of nonlinear interaction between photons in the three-mode cavity. This availability is testified via numerical analysis. It also considers both the situations with and without dissipation.展开更多
Recently, Peng et al. [2010 Eur. Phys. J. D 58 403] proposed to teleport an arbitrary two-qubit state with a family of four-qubit entangled states, which simultaneously include the tensor product of two Bell states, l...Recently, Peng et al. [2010 Eur. Phys. J. D 58 403] proposed to teleport an arbitrary two-qubit state with a family of four-qubit entangled states, which simultaneously include the tensor product of two Bell states, linear cluster state and Dicke-class state. This paper proposes to implement their scheme in cavity quantum electrodynamics and then presents a new family of four-qubit entangled state ｜Ω/1234. It simultaneously includes all the well-known four-qubit entangled states which can be used to teleport an arbitrary two-qubit state. The distinct advantage of the scheme is that it only needs a single setup to prepare the whole family of four-qubit entangled states, which will be very convenient for experimental realization. After discussing the experimental condition in detail, we show the scheme may be feasible based on present technology in cavity quantum electrodynamics.展开更多
Gauge potential plays an important role in exploring exotic phenomena in the single- and many-body quantum systems.In this paper,we propose a scheme to create both new Abelian and non-Abelian gauge potentials by adiab...Gauge potential plays an important role in exploring exotic phenomena in the single- and many-body quantum systems.In this paper,we propose a scheme to create both new Abelian and non-Abelian gauge potentials by adiabatically controlling the degenerate Dicke model in cavity quantum electrodynamics.It is shown that a non-Abelian gauge potential is achieved only for a single atom,whereas an Abelianizen diagonal gauge potential is realized for the atomic ensemble.More importantly,two interesting quantum phenomena such as the geometric phase and the magnetic monopole induced by our created gauge potentials are also predicted.The possible physical realization is presented in the macroscopic circuit quantum electrodynamics with the Cooper pair boxes,which act as the artificial two-level atoms controlled by the gate voltage and the external magnetic flux.展开更多
A scheme is proposed for generating a three-dimensional entangled state for two atoms trapped in a cavity by one step via adiabatic passage. In the scheme, the two atoms are always in ground states and the field mode ...A scheme is proposed for generating a three-dimensional entangled state for two atoms trapped in a cavity by one step via adiabatic passage. In the scheme, the two atoms are always in ground states and the field mode of the cavity excited is negligible under a certain condition. Therefore, the scheme is very robust against decoherence. Furthermore, it needs neither the exact control of all parameters nor the accurate control of the interaction time. It is shown that qutrit entanglement can be generated with a high fidelity.展开更多
This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom （as target qubit） sent through a two-mode cavity （as control qubits）. The first scheme is based on the large-detuning atom cav...This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom （as target qubit） sent through a two-mode cavity （as control qubits）. The first scheme is based on the large-detuning atom cavity field interaction and the second scheme is based on the resonant atom-field interaction. Both the situations with and without cavity decay and atomic spontaneous emission are considered. The advantages and the experimental feasibility of these two schemes are discussed.展开更多
We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the ho...We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the holes. This structure has two functionalities:(1) tweezers for optical trapping;(2) a plasmonic resonant cavity for quantum electrodynamics. The electromagnetic response of the cavity is calculated by finite-difference time-domain(FDTD) simulations, and the optical force is characterized based on the Maxwell's stress tensor method. To be tweezers, this structure tends to trap quantum dots at the edges of its tips where light is significantly confined. To be a plasmonic cavity, its plasmonic resonant mode interacts strongly with the trapped quantum dots due to the enhanced electric field. Rabi splitting and anti-crossing phenomena are observed in the calculated scattering spectra, demonstrating that a strong-coupling regime has been achieved. The method present here provides a robust way to position a single quantum dot in a nanocavity for investigating cavity quantum electrodynamics.展开更多
We present a qubit-loss-free(QLF)fusion scheme for generating large-scale atom W states in cavity quantum electrodynamics(QED)system.Compared to the most current fusion schemes which are conditioned on the case where ...We present a qubit-loss-free(QLF)fusion scheme for generating large-scale atom W states in cavity quantum electrodynamics(QED)system.Compared to the most current fusion schemes which are conditioned on the case where one particle can be extracted from each initial W state to the fusion process,our scheme will access one or two particles from each W state.Based on the atom–cavity-field detuned interaction,three jWin+m+t states can be generated from the jWin,jWim,and jWit states with the help of two auxiliary atoms,and three jWin+m+t+q states can be generated from jWin,jWim,jWit,and a jWiq state with the help of three auxiliary atoms.Comparing the numerical simulations of the resource cost of fusing three small-size W states based on the previous schemes,our fusion scheme seems to be more efficient.This QLF fusion scheme can be generalized to the case of fusing k different or identical particle W states.Furthermore,with no qubit loss,it greatly reduces the number of fusion steps and prepares W states with larger particle numbers.展开更多
An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics （QED） is proposed in this paper. The prominent advantage of our scheme is that the success...An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics （QED） is proposed in this paper. The prominent advantage of our scheme is that the successful probability of the dense coding with a W-class state can reach 1. In addition, the scheme can be implemented by the present cavity QED techniques.展开更多
An experimentally feasible scheme for implementing four-atom quantum dense coding of an atom-cavity system is proposed. The cavity is only virtually excited and no quantum information will be transferred from the atom...An experimentally feasible scheme for implementing four-atom quantum dense coding of an atom-cavity system is proposed. The cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity. Thus the scheme is insensitive to cavity decay and the thermal field. In the scheme, Alice can send faithfully 4 bits of classical information to Bob by sending two qubits. Generalized Bell states can be exactly distinguished by detecting the atomic state, and quantum dense coding can be realized in a simple way.展开更多
This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quant...This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity during the preparation for a four-atom entangled cluster state, and thus the scheme is insensitive to the cavity field states and cavity decay. Assuming that deviation of laser intensity is 0.01 and that of simultaneity for the interaction is 0.01, it shows that the fidelity of the resulting four-atom entangled cluster state is about 0.9886. The scheme can also be used to generate a four-ion entangled cluster state in a hot trapped-ion system. Assuming that deviation of laser intensity is 0.01, it shows that the fidelity of the resulting four-ion entangled cluster state is about 0.9990. Experimental feasibility for achieving this scheme is also discussed.展开更多
Semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, in- tensive researches have been carried out and diverse kinds of qubits based on different types of se...Semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, in- tensive researches have been carried out and diverse kinds of qubits based on different types of semiconductor quantum dots were developed. Recent advances prove high fidelity single and two qubit gates, and even prototype quantum algorithms. These breakthroughs motivate further research on realizing a fault tolerant quantum computer. In this paper we review the main principles of various semiconductor quantum dot based qubits and the latest associated experimental results. Finally the future trends of those qubits will be discussed.展开更多
The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement ...The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord.展开更多
We present a scheme for implementing a three-qubit phase gate via manipulating rf superconducting quantum interference device （SQUID） qubits in the decoherence-free subspace with respect to cavity decay. Through app...We present a scheme for implementing a three-qubit phase gate via manipulating rf superconducting quantum interference device （SQUID） qubits in the decoherence-free subspace with respect to cavity decay. Through appropriate changes of the coupling constants between rf SQUIDs and cavity, the scheme can be realized only in one step. A high fidelity is obtained even in the presence of decoherence.展开更多
We investigate the self-trapping of a Bose Josephson junction, which is dispersively coupled to a driven optical cavity. The cavity-induced nonlinearity is presented analytically, and its effect results in the appeara...We investigate the self-trapping of a Bose Josephson junction, which is dispersively coupled to a driven optical cavity. The cavity-induced nonlinearity is presented analytically, and its effect results in the appearance of the self-trapping for the Bose-Einstein condensates in the Josephson oscillation regime. In addition, there exists competition between the nonlinearities induced by the interatomic interaction and by the driven cavity for the emergences of self-trapping. Our results show that the driven cavity can be utilized as a possible tool to produce the self-trapping for the condensates with weak interatomic interaction.展开更多
In this paper, we propose a physical scheme to concentrate non-maximally entangled atomic pure states by using atomic collision in a far-off-resonant cavity. The most distinctive advantage of our scheme is that the no...In this paper, we propose a physical scheme to concentrate non-maximally entangled atomic pure states by using atomic collision in a far-off-resonant cavity. The most distinctive advantage of our scheme is that the non-maximally entangled atoms may be far from or near each other and their degree of entanglement can be maximally amplified. The photon-number-dependent parts in the effective Hamiltonian are cancelled with the assistance of a strong classical field, thus the scheme is insensitive to both the cavity decay and the thermal field.展开更多
We study the statistics of the emitted filed from Rydberg atom confined inside a microcavity and interacting with a pump laser in the strong coupling regime. We explore the manifestation of the antibunching in connect...We study the statistics of the emitted filed from Rydberg atom confined inside a microcavity and interacting with a pump laser in the strong coupling regime. We explore the manifestation of the antibunching in connection with the internal system parameters.展开更多
We present a theoretical study of an optical cavity coupled with single four-level atoms in closed loop formed via applied control lasers. The transmitted probe field from the cavity is analyzed. We show that the elec...We present a theoretical study of an optical cavity coupled with single four-level atoms in closed loop formed via applied control lasers. The transmitted probe field from the cavity is analyzed. We show that the electromagnetically induced transparency（EIT） in the cavity and the normal mode splitting will be very different with changing the closed interaction phase and the intensity of the free-space control laser. This coupled cavity-atom system presents a variational double-EIT that comes from modulating the splitting of the dark state, which means that we could realize the gradual transfer between one EIT peak and two EIT peaks by adjusting the applied control lasers, and the normal mode splitting sidebands will shift slightly by changing the free-space control laser. This means that we could control the output cavity probe field more freely and it is easer to realize optical switch controlled by more parameters. We also depict the angular dispersion of the intracavity probe field in different free-space control laser. The large phase shift（-π → π） of the reflected intracavity probe field will be very useful for optical temporal differentiation and quantum phase gate.展开更多
We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics （CQED）. Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mod...We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics （CQED）. Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mode cavity field and a classical laser, and both the symmetric and asymmetric W states can be created in a single step. Our schemes are insensitive to both the cavity decay and atomic spontaneous emission. With the above system, we also propose a scheme for realizing quantum-information concentration which is the reverse process of quantum cloning. In this scheme, quantum-information originally coming from a single qubit, but now distributed into many qubits, is concentrated back to a single qubit in onlv one steP.展开更多
A protocol is proposed to generate atomic entangled states and implement quantum information transfer in a cavity quantum electrodynamics system. It utilizes Raman transitions or stimulated Raman adiabatic passages be...A protocol is proposed to generate atomic entangled states and implement quantum information transfer in a cavity quantum electrodynamics system. It utilizes Raman transitions or stimulated Raman adiabatic passages between two systems to entangle the ground states of two three-state A-type atoms trapped in a single mode cavity. It does not need the measurements on cavity field nor atomic detection and can be implemented in a deterministic fashion. Since the present protocol is insensitive to both cavity decay and atomic spontaneous emission, it may have some interesting applications in quantum information processing.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504272,11774262,11474003,and 11504003)the National Key Basic Research Special Foundation(Grant No.2016YFA0302800)+2 种基金the Joint Fund of the National Natural Science Foundation of China(Grant No.U1330203)the Fund from the Shanghai Science and Technology Committee(STCSM)(Grant No.18JC1410900)the Natural Science Foundation of Anhui Province,China(Grant Nos.1408085MA19 and 1608085ME102)
文摘We theoretically study the collective decay of two atoms trapped in a single mode cavity and we describe the evolution of the population of Dicke states. We show that the collective decay property is strongly dependent on the phase of atomic radiation and the speeding up of collective decay can only be observed in a bad cavity regime. For in-or out-phase case,this occurs due to the quantum interference enhancement, no matter which atom is excited initially. For π/2 phase, the speeding up of collective decay takes place if the first atom is excited at the beginning. However, it disappears due to the quantum interference cancellation if the second atom is excited. Compared with the in-phase and out-phase cases,we also show that the speeding up of collective decay can be significantly enhanced in strong coupling regime for π/2 phase, although one atom is decoupled to the cavity in this condition. The study presented here is helpful to understand the physical mechanism of collective decay in cavity quantum electrodynamics and it provides a useful method to control the collective decay phenomenon via quantum interference effect.
基金supported by the National Natural Science Foundation of China (Grant No 60667001)
文摘This paper presents a scheme for implementing a Fredkin gate on three modes of a cavity. The scheme is based on the dispersive atom-cavity interaction. By modulating the cavity frequency and the atomic transition frequency appropriately, it obtains the effective form of nonlinear interaction between photons in the three-mode cavity. This availability is testified via numerical analysis. It also considers both the situations with and without dissipation.
文摘Recently, Peng et al. [2010 Eur. Phys. J. D 58 403] proposed to teleport an arbitrary two-qubit state with a family of four-qubit entangled states, which simultaneously include the tensor product of two Bell states, linear cluster state and Dicke-class state. This paper proposes to implement their scheme in cavity quantum electrodynamics and then presents a new family of four-qubit entangled state ｜Ω/1234. It simultaneously includes all the well-known four-qubit entangled states which can be used to teleport an arbitrary two-qubit state. The distinct advantage of the scheme is that it only needs a single setup to prepare the whole family of four-qubit entangled states, which will be very convenient for experimental realization. After discussing the experimental condition in detail, we show the scheme may be feasible based on present technology in cavity quantum electrodynamics.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10904092,10934004,60978018,11074184,and 11074154the Zhejiang Provincial Natural Science Foundation under Grant No.Y6090001
文摘Gauge potential plays an important role in exploring exotic phenomena in the single- and many-body quantum systems.In this paper,we propose a scheme to create both new Abelian and non-Abelian gauge potentials by adiabatically controlling the degenerate Dicke model in cavity quantum electrodynamics.It is shown that a non-Abelian gauge potential is achieved only for a single atom,whereas an Abelianizen diagonal gauge potential is realized for the atomic ensemble.More importantly,two interesting quantum phenomena such as the geometric phase and the magnetic monopole induced by our created gauge potentials are also predicted.The possible physical realization is presented in the macroscopic circuit quantum electrodynamics with the Cooper pair boxes,which act as the artificial two-level atoms controlled by the gate voltage and the external magnetic flux.
基金supported by the Science Foundation of Educational Committee of Fujian Province of China (Grant Nos. JB09012 and JB09013)
文摘A scheme is proposed for generating a three-dimensional entangled state for two atoms trapped in a cavity by one step via adiabatic passage. In the scheme, the two atoms are always in ground states and the field mode of the cavity excited is negligible under a certain condition. Therefore, the scheme is very robust against decoherence. Furthermore, it needs neither the exact control of all parameters nor the accurate control of the interaction time. It is shown that qutrit entanglement can be generated with a high fidelity.
基金supported by the National Natural Science Foundation of China (Grant No 60667001)
文摘This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom （as target qubit） sent through a two-mode cavity （as control qubits）. The first scheme is based on the large-detuning atom cavity field interaction and the second scheme is based on the resonant atom-field interaction. Both the situations with and without cavity decay and atomic spontaneous emission are considered. The advantages and the experimental feasibility of these two schemes are discussed.
基金National Key R&D Program of China(2016YFA0301300)
文摘We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the holes. This structure has two functionalities:(1) tweezers for optical trapping;(2) a plasmonic resonant cavity for quantum electrodynamics. The electromagnetic response of the cavity is calculated by finite-difference time-domain(FDTD) simulations, and the optical force is characterized based on the Maxwell's stress tensor method. To be tweezers, this structure tends to trap quantum dots at the edges of its tips where light is significantly confined. To be a plasmonic cavity, its plasmonic resonant mode interacts strongly with the trapped quantum dots due to the enhanced electric field. Rabi splitting and anti-crossing phenomena are observed in the calculated scattering spectra, demonstrating that a strong-coupling regime has been achieved. The method present here provides a robust way to position a single quantum dot in a nanocavity for investigating cavity quantum electrodynamics.
基金the National Natural Science Foun-dation of China(Grant No.12204311)the Jiangxi Natural Science Foundation(Grant No.20224BAB211025).
文摘We present a qubit-loss-free(QLF)fusion scheme for generating large-scale atom W states in cavity quantum electrodynamics(QED)system.Compared to the most current fusion schemes which are conditioned on the case where one particle can be extracted from each initial W state to the fusion process,our scheme will access one or two particles from each W state.Based on the atom–cavity-field detuned interaction,three jWin+m+t states can be generated from the jWin,jWim,and jWit states with the help of two auxiliary atoms,and three jWin+m+t+q states can be generated from jWin,jWim,jWit,and a jWiq state with the help of three auxiliary atoms.Comparing the numerical simulations of the resource cost of fusing three small-size W states based on the previous schemes,our fusion scheme seems to be more efficient.This QLF fusion scheme can be generalized to the case of fusing k different or identical particle W states.Furthermore,with no qubit loss,it greatly reduces the number of fusion steps and prepares W states with larger particle numbers.
基金supported by the National Natural Science Foundation of China (Grant No 10674001)the Program of Education Department of Anhui University of China (Grant No KJ2007A002)the Youth Program of Fuyang Normal College of China (Grant No 2005LQ04)
文摘An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics （QED） is proposed in this paper. The prominent advantage of our scheme is that the successful probability of the dense coding with a W-class state can reach 1. In addition, the scheme can be implemented by the present cavity QED techniques.
基金Project supported by the Postdoctal Foundation of Central South University of China, the Important Program of Hunan Provincial Education Department (Grant No. 06A038)Department of Education of Hunan Province of China (Grant No. 06C080)Hunan Provincial Natural Science Foundation, China (Grant No. 07JJ3013)
文摘An experimentally feasible scheme for implementing four-atom quantum dense coding of an atom-cavity system is proposed. The cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity. Thus the scheme is insensitive to cavity decay and the thermal field. In the scheme, Alice can send faithfully 4 bits of classical information to Bob by sending two qubits. Generalized Bell states can be exactly distinguished by detecting the atomic state, and quantum dense coding can be realized in a simple way.
基金Project supported by the Postdoctal Foundation of Central South University of Chinathe Important Program of Hunan Provincial Education Department of China (Grant No. 06A038)+1 种基金Department of Education of Hunan Province of China (Grant No. 06C080)Hunan Provincial Natural Science Foundation,China (Grant No. 07JJ3013)
文摘This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity during the preparation for a four-atom entangled cluster state, and thus the scheme is insensitive to the cavity field states and cavity decay. Assuming that deviation of laser intensity is 0.01 and that of simultaneity for the interaction is 0.01, it shows that the fidelity of the resulting four-atom entangled cluster state is about 0.9886. The scheme can also be used to generate a four-ion entangled cluster state in a hot trapped-ion system. Assuming that deviation of laser intensity is 0.01, it shows that the fidelity of the resulting four-ion entangled cluster state is about 0.9990. Experimental feasibility for achieving this scheme is also discussed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0301700)the National Natural Science Foundation of China(Grant Nos.61674132,11674300,11575172,and 11625419)the Fundamental Research Fund for the Central Universities
文摘Semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, in- tensive researches have been carried out and diverse kinds of qubits based on different types of semiconductor quantum dots were developed. Recent advances prove high fidelity single and two qubit gates, and even prototype quantum algorithms. These breakthroughs motivate further research on realizing a fault tolerant quantum computer. In this paper we review the main principles of various semiconductor quantum dot based qubits and the latest associated experimental results. Finally the future trends of those qubits will be discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174254)the National Basic Research Program of China (Grant Nos. 2011CBA00103 and 2009CB929104)
文摘The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord.
基金Project supported by the National Natural Science Foundation of China (Grant No 60667001)
文摘We present a scheme for implementing a three-qubit phase gate via manipulating rf superconducting quantum interference device （SQUID） qubits in the decoherence-free subspace with respect to cavity decay. Through appropriate changes of the coupling constants between rf SQUIDs and cavity, the scheme can be realized only in one step. A high fidelity is obtained even in the presence of decoherence.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10847006 and 10874142
文摘We investigate the self-trapping of a Bose Josephson junction, which is dispersively coupled to a driven optical cavity. The cavity-induced nonlinearity is presented analytically, and its effect results in the appearance of the self-trapping for the Bose-Einstein condensates in the Josephson oscillation regime. In addition, there exists competition between the nonlinearities induced by the interatomic interaction and by the driven cavity for the emergences of self-trapping. Our results show that the driven cavity can be utilized as a possible tool to produce the self-trapping for the condensates with weak interatomic interaction.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘In this paper, we propose a physical scheme to concentrate non-maximally entangled atomic pure states by using atomic collision in a far-off-resonant cavity. The most distinctive advantage of our scheme is that the non-maximally entangled atoms may be far from or near each other and their degree of entanglement can be maximally amplified. The photon-number-dependent parts in the effective Hamiltonian are cancelled with the assistance of a strong classical field, thus the scheme is insensitive to both the cavity decay and the thermal field.
文摘We study the statistics of the emitted filed from Rydberg atom confined inside a microcavity and interacting with a pump laser in the strong coupling regime. We explore the manifestation of the antibunching in connection with the internal system parameters.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174109)
文摘We present a theoretical study of an optical cavity coupled with single four-level atoms in closed loop formed via applied control lasers. The transmitted probe field from the cavity is analyzed. We show that the electromagnetically induced transparency（EIT） in the cavity and the normal mode splitting will be very different with changing the closed interaction phase and the intensity of the free-space control laser. This coupled cavity-atom system presents a variational double-EIT that comes from modulating the splitting of the dark state, which means that we could realize the gradual transfer between one EIT peak and two EIT peaks by adjusting the applied control lasers, and the normal mode splitting sidebands will shift slightly by changing the free-space control laser. This means that we could control the output cavity probe field more freely and it is easer to realize optical switch controlled by more parameters. We also depict the angular dispersion of the intracavity probe field in different free-space control laser. The large phase shift（-π → π） of the reflected intracavity probe field will be very useful for optical temporal differentiation and quantum phase gate.
基金Project supported by the Key Scientific Research Fund of the Educational Department of Hunan Province of China (Grant No. 09A013)Science Foundation of Hengyang Normal University of China (Grant No. 09A28)
文摘We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics （CQED）. Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mode cavity field and a classical laser, and both the symmetric and asymmetric W states can be created in a single step. Our schemes are insensitive to both the cavity decay and atomic spontaneous emission. With the above system, we also propose a scheme for realizing quantum-information concentration which is the reverse process of quantum cloning. In this scheme, quantum-information originally coming from a single qubit, but now distributed into many qubits, is concentrated back to a single qubit in onlv one steP.
基金Project supported by the National Basic Research Program of China (Grant No.2010CB923102)the National Natural Science Foundation of China (Grant No.11074199)
文摘A protocol is proposed to generate atomic entangled states and implement quantum information transfer in a cavity quantum electrodynamics system. It utilizes Raman transitions or stimulated Raman adiabatic passages between two systems to entangle the ground states of two three-state A-type atoms trapped in a single mode cavity. It does not need the measurements on cavity field nor atomic detection and can be implemented in a deterministic fashion. Since the present protocol is insensitive to both cavity decay and atomic spontaneous emission, it may have some interesting applications in quantum information processing.
