We propose a scheme for generating an N-atom cluster state via cavity quantum electrodynamics ( CQED). In our scheme, there is no transfer of quantum information between the atoms and the cavity, i.e., the cavity is...We propose a scheme for generating an N-atom cluster state via cavity quantum electrodynamics ( CQED). In our scheme, there is no transfer of quantum information between the atoms and the cavity, i.e., the cavity is always in the vacuum state, so the cavity decay can be suppressed. Also, the generated cluster state is the entanglement of the ground states, so the atomic spontaneous emission can be avoided. Therefore, the cluster state generated in our scheme has a longer lifetime. Furthermore, the requirement on the quality factor of the cavity greatly loosened for the cavity is only virtually excited.展开更多
We propose a scheme for generating a genuine four-particle polarisation entangled state |χ^00) that has many interesting entanglement properties and potential applications in quantum information processing. In our ...We propose a scheme for generating a genuine four-particle polarisation entangled state |χ^00) that has many interesting entanglement properties and potential applications in quantum information processing. In our scheme, we use the weak cross-Kerr nonlinear interaction between field-modes and the non-demolition measurement method based on highly efficient homodyne detection, which is feasible under the current experiment conditions.展开更多
For the first time,we derive the compact forms of normalization factors for photon-added(-subtracted) two-mode squeezed thermal states by using the P-representation and the integration within an ordered product of o...For the first time,we derive the compact forms of normalization factors for photon-added(-subtracted) two-mode squeezed thermal states by using the P-representation and the integration within an ordered product of operators(IWOP) technique.It is found that these two factors are related to the Jacobi polynomials.In addition,some new relationships for Jacobi polynomials are presented.展开更多
We propose a scheme to generate the controlled phase gate by using an electron floating on liquid helium.The electron is also driven by a classical laser beam and by an oscillating magnetic field.In the process,the vi...We propose a scheme to generate the controlled phase gate by using an electron floating on liquid helium.The electron is also driven by a classical laser beam and by an oscillating magnetic field.In the process,the vibration of the electron is used as the qubus to couple the energy level qubit(1D Stark-shifted hydrogen)and spin qubit.Ultimately,the controlled phase gate can be generated.展开更多
We propose a scheme for generating squeezed states based on a superconducting hybrid system. Our system consists of a nanomeehanical resonator, a superconducting flux qubit, and a superconducting transmission line res...We propose a scheme for generating squeezed states based on a superconducting hybrid system. Our system consists of a nanomeehanical resonator, a superconducting flux qubit, and a superconducting transmission line resonator. Using our proposal, one can easily generate the squeezed states of the nanomechanical resonator. In our scheme, the nonlinear interaction between the nanomechanical resonator and the superconducting transmission line resonator can be implemented by the flux qubit as 'nonlinear media' with a tunable Josephson energy. The realization of the nonlinearity does not need any operations on the flux qubit and just needs to adiabatically keep it at the ground state, which can greatly decrease the effect of the decoherenee of the flux qubit on the squeezed ef^ciency.展开更多
We propose a scheme for realizing two-qubit controlled phase gates on two nonidentical quantum dots trapped in separate cavities. In our scheme, each dot simultaneously interacts with one highly detuned cavity mode an...We propose a scheme for realizing two-qubit controlled phase gates on two nonidentical quantum dots trapped in separate cavities. In our scheme, each dot simultaneously interacts with one highly detuned cavity mode and two strong driven classical fields. During the gate operation, the quantum dots undergo no transition, while the system can acquire different phases conditional on different states of the quantum dots. With the application of the single-qubit operations, two-qubit controlled phase gates can be realized.展开更多
We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to...We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to the realisation of an arbitrary N-qubit phase gate by appropriately adjusting coupling strengths and detunings between atoms and external driving fields. The advantage of this one-step scheme is its robustness against decoherence.展开更多
Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in ...Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.展开更多
Using deformed boson algebra,we study the property of two-mode coherent states in noncommutative phase space.When a two-mode field evolves in the noncommutative phase space,it can acquire an extra θ-dependent phase c...Using deformed boson algebra,we study the property of two-mode coherent states in noncommutative phase space.When a two-mode field evolves in the noncommutative phase space,it can acquire an extra θ-dependent phase compared to the case of commutative space.This phase is detectable and may be used to test noncommutativity.展开更多
We propose a scheme for implementing quantum information transfer based on frequency modes of microwave photons in a superconducting circuit.In our proposal,quantum information can be encoded on frequency modes of mic...We propose a scheme for implementing quantum information transfer based on frequency modes of microwave photons in a superconducting circuit.In our proposal,quantum information can be encoded on frequency modes of microwave photons,which act as a qubit in the resonator.Operations for the qubit,which is a process involving parametric frequency conversion,can be implemented by adjusting biased-dc superconducting quantum interference(SQUID).The coupling between two resonators can be controlled by tuning the frequency of the LC circuit inserted by a dc SQUID with two Josephson-junctions(2JJ-SQUID).Compared with previous ones,our work can avoid dephasing and decoherence resulting from atom decay.In addition,the resonator which includes multiple photons in two frequency modes can play a role of an identical atomic ensemble,which could lead to photon blockade.展开更多
Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tightbinding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles w...Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tightbinding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schro¨dinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given.展开更多
We propose a scheme for realizing the 1 → 2 universal quantum cloning machine (UQCM) with superconducting quantum interference device (SQUID) qubits in circuit quantum electrodynamics (circuit QED). In this sch...We propose a scheme for realizing the 1 → 2 universal quantum cloning machine (UQCM) with superconducting quantum interference device (SQUID) qubits in circuit quantum electrodynamics (circuit QED). In this scheme, in order to implement UQCM, we only need phase shift gate operation on SQUID qubits and the Raman transitions. The cavity number we need is only one. Thus our scheme is simple and has advantages in the experimental realization. Furthermore, both the cavity and the SQUID qubits are virtually excited, so the decoherence can be neglected.展开更多
An unknown state of a quantum system S is usually determined by repeatedly measuring a set of non-commuting observables. The state can also be obtained from the repeated measurements of a single separable observable w...An unknown state of a quantum system S is usually determined by repeatedly measuring a set of non-commuting observables. The state can also be obtained from the repeated measurements of a single separable observable when the system S interacts with an assistant system A in a known state. In this paper, we study the quantum state tomography of a three-level atom (the system S ) interacting with two radiation fields as the assistant system A. We obtain the initial state of S by repeatedly measuring a separable observable =zn1n2, in which z is the atom operator, and n 1 and n 2 are the photon number operators of the two radiation fields. We achieve the one-to-one mapping M between the initial density matrix of the system S and the measured results of the single separable observable. We also give a concrete numerical example.展开更多
We show that controlled-controlled-NOT(CCN)operation-based entanglement purification protocol can be further improved.CCN protocol requires Bell state measurements after performing the CCN operations.In the original...We show that controlled-controlled-NOT(CCN)operation-based entanglement purification protocol can be further improved.CCN protocol requires Bell state measurements after performing the CCN operations.In the original CCN protocol,the measured states are assumed to be destroyed.However,if controlled-NOT gates are used to perform such Bell state measurements,in some unsuccessful situations of the CCN protocol,one can further purify the two mixed entangled states which are to be measured.In this way,the total efficiency of the CCN protocol is further increased.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 60578055, and the National Key Basic Research Program of China under Grant Nos 2007CB925204 and 2009CB929604.
文摘We propose a scheme for generating an N-atom cluster state via cavity quantum electrodynamics ( CQED). In our scheme, there is no transfer of quantum information between the atoms and the cavity, i.e., the cavity is always in the vacuum state, so the cavity decay can be suppressed. Also, the generated cluster state is the entanglement of the ground states, so the atomic spontaneous emission can be avoided. Therefore, the cluster state generated in our scheme has a longer lifetime. Furthermore, the requirement on the quality factor of the cavity greatly loosened for the cavity is only virtually excited.
基金supported by the National Natural Science Foundation of China (Grant No.60978009 )the National Basic Research Program of China (Grant Nos.2009CB929604 and 2007CB925204)
文摘We propose a scheme for generating a genuine four-particle polarisation entangled state |χ^00) that has many interesting entanglement properties and potential applications in quantum information processing. In our scheme, we use the weak cross-Kerr nonlinear interaction between field-modes and the non-demolition measurement method based on highly efficient homodyne detection, which is feasible under the current experiment conditions.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11264018 and 60978009)the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91121023)+1 种基金the National Basic Research Project of China (Grant No. 2011CBA00200)the Young Talents Foundation of Jiangxi Normal University,China
文摘For the first time,we derive the compact forms of normalization factors for photon-added(-subtracted) two-mode squeezed thermal states by using the P-representation and the integration within an ordered product of operators(IWOP) technique.It is found that these two factors are related to the Jacobi polynomials.In addition,some new relationships for Jacobi polynomials are presented.
基金Supported by the National Natural Science Foundation of China under Grant No 60978009the National Basic Research Program of China under Grant Nos 2009CB929604 and 2007CB925204.
文摘We propose a scheme to generate the controlled phase gate by using an electron floating on liquid helium.The electron is also driven by a classical laser beam and by an oscillating magnetic field.In the process,the vibration of the electron is used as the qubus to couple the energy level qubit(1D Stark-shifted hydrogen)and spin qubit.Ultimately,the controlled phase gate can be generated.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274043 and 60978009the Major Research Plan of the National Natural Science Foundation of China under Grant No 91121023
文摘We propose a scheme for generating squeezed states based on a superconducting hybrid system. Our system consists of a nanomeehanical resonator, a superconducting flux qubit, and a superconducting transmission line resonator. Using our proposal, one can easily generate the squeezed states of the nanomechanical resonator. In our scheme, the nonlinear interaction between the nanomechanical resonator and the superconducting transmission line resonator can be implemented by the flux qubit as 'nonlinear media' with a tunable Josephson energy. The realization of the nonlinearity does not need any operations on the flux qubit and just needs to adiabatically keep it at the ground state, which can greatly decrease the effect of the decoherenee of the flux qubit on the squeezed ef^ciency.
基金supported by the National Natural Science Foundation of China(Grant No.60978009)the National Basic Research Program of China(Grant Nos.2007CB925204 and 2009CB929604)
文摘We propose a scheme for realizing two-qubit controlled phase gates on two nonidentical quantum dots trapped in separate cavities. In our scheme, each dot simultaneously interacts with one highly detuned cavity mode and two strong driven classical fields. During the gate operation, the quantum dots undergo no transition, while the system can acquire different phases conditional on different states of the quantum dots. With the application of the single-qubit operations, two-qubit controlled phase gates can be realized.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60578055 and 60978009)the National Basic Research Program of China(Grant Nos. 2007CB925204 and 2009CB929604)
文摘We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to the realisation of an arbitrary N-qubit phase gate by appropriately adjusting coupling strengths and detunings between atoms and external driving fields. The advantage of this one-step scheme is its robustness against decoherence.
基金Project supported by the Key Projects in the Guangzhou Science & Technology Pillar Program of China(Grant No.2008Z1-D501)the Guangdong Key Technologies Research & Development Program of China(Grant No.2007B010400009)+1 种基金the Guangdong Polytechnic Institute Scientific Research Fund,China(Grant No.0901)the Key Laboratory Program of Quantum Information of Chinese Academy of Sciences
文摘Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074079 and 60978009the Major Research Plan of the National Natural Science Foundation of China under Grant No 91121023+1 种基金the National Basic Research Program of China under Grant No 2011CBA00200the Ph.D.Program Foundation of Ministry of Education of China.
文摘Using deformed boson algebra,we study the property of two-mode coherent states in noncommutative phase space.When a two-mode field evolves in the noncommutative phase space,it can acquire an extra θ-dependent phase compared to the case of commutative space.This phase is detectable and may be used to test noncommutativity.
基金Supported by the National Natural Science Foundation of China under Grant No 60978009the Major Research Plan of the National Natural Science Foundation of China under Grant No 91121023the SKPBR of China(No 2011CBA00200).
文摘We propose a scheme for implementing quantum information transfer based on frequency modes of microwave photons in a superconducting circuit.In our proposal,quantum information can be encoded on frequency modes of microwave photons,which act as a qubit in the resonator.Operations for the qubit,which is a process involving parametric frequency conversion,can be implemented by adjusting biased-dc superconducting quantum interference(SQUID).The coupling between two resonators can be controlled by tuning the frequency of the LC circuit inserted by a dc SQUID with two Josephson-junctions(2JJ-SQUID).Compared with previous ones,our work can avoid dephasing and decoherence resulting from atom decay.In addition,the resonator which includes multiple photons in two frequency modes can play a role of an identical atomic ensemble,which could lead to photon blockade.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11004063) and the Fundamental Research Funds for the Central Universmes, China (Grant No. 2012ZZ0076).
文摘Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tightbinding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schro¨dinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60978009 and 60578055, and by the National Basic Research Program of China under Grant Nos 2009CB929604 and 2007CB925204.
文摘We propose a scheme for realizing the 1 → 2 universal quantum cloning machine (UQCM) with superconducting quantum interference device (SQUID) qubits in circuit quantum electrodynamics (circuit QED). In this scheme, in order to implement UQCM, we only need phase shift gate operation on SQUID qubits and the Raman transitions. The cavity number we need is only one. Thus our scheme is simple and has advantages in the experimental realization. Furthermore, both the cavity and the SQUID qubits are virtually excited, so the decoherence can be neglected.
基金the National Natural Science Foundation of China (Grant Nos. 60978009 and 91121023)the National Basic Research Program of China (Grant No. 2011CBA00200)
文摘An unknown state of a quantum system S is usually determined by repeatedly measuring a set of non-commuting observables. The state can also be obtained from the repeated measurements of a single separable observable when the system S interacts with an assistant system A in a known state. In this paper, we study the quantum state tomography of a three-level atom (the system S ) interacting with two radiation fields as the assistant system A. We obtain the initial state of S by repeatedly measuring a separable observable =zn1n2, in which z is the atom operator, and n 1 and n 2 are the photon number operators of the two radiation fields. We achieve the one-to-one mapping M between the initial density matrix of the system S and the measured results of the single separable observable. We also give a concrete numerical example.
基金supportedby the National Natural Science Foundation of China(No.11074079)the Doctoral Fund of Ministry of Education of China
文摘We show that controlled-controlled-NOT(CCN)operation-based entanglement purification protocol can be further improved.CCN protocol requires Bell state measurements after performing the CCN operations.In the original CCN protocol,the measured states are assumed to be destroyed.However,if controlled-NOT gates are used to perform such Bell state measurements,in some unsuccessful situations of the CCN protocol,one can further purify the two mixed entangled states which are to be measured.In this way,the total efficiency of the CCN protocol is further increased.