利用绝热过程实现量子信息转移

基于绝热过程,仅需一个真空腔即可分别实现未知单原子态、双原子纠缠态及GHZ态的转移.在这些方案中,量子信息都存储在原子的基态,且系统仅在暗态空间中演化,原子激发态上无布居,这使得原子的自发辐射效应大大受到抑制.相比之前的方案,这些方案所需资源更少,操作更简单.另外,还讨论了其在实验上实现的可行性.     

利用绝热过程制备W态

提出一种利用绝热过程制备多原子W态的方案.本方案可有效地抑制原子的自发辐射噪声.利用相似的方法可制备腔场W态.制备成功的几率约为1.0.     

Transferring a Multi-atom Entangled State via Adiabatic Passage

We present a scheme for transferring atomic entangled states via adiabatic passage. In the scheme, we use photons to achieve efficient quantum transmission among spatially distant atoms. The probability of the successful transferring quantum state approaches 1. Meanwhile, the scheme is robust against the effects of atomic spontaneous emission.     

Quantum Phase Gates for Trapped Ions via Adiabatic Passage

We propose a scheme to produce quantum phase gates for trapped ions. Taking advantage of the adiabatic evolution, the operation is insensitive to small fluctuations of experimental parameters. Furthermore, the spontaneous emission is suppressed since the ions have no probability of being populated in the electronic excited states.     

Teleportation of an Unknown Atomic State via Adiabatic Passage

We propose a scheme for teleporting an unknown atomic state via adiabatic passage. Taking advantage of adiabatic passage, the atom has no probability of being excited and thus the atomic spontaneous emission is suppressed. We also show that the fidelity can reach 1 under certain condition.     

Fast Hybrid Quantum State Transfer and Entanglement Generation via No Transition Passage

Quantum information processing requires information or entanglement that can be transferred or distributed from one location to another with high fidelity. Here, a scheme for faithful quantum state transfer and entanglement generation based on the hybrid opto‐electro‐mechanical (OEM) systems in a fast and deterministic way is proposed. By applying invariant‐based inverse engineering to the interaction Hamiltonian, the couplings in the OEM system can be controlled by asynchronized driving fields, which is convenient to be realized in practice. Taking the systematic decoherence into consideration, the numerical simulation shows that the scheme can be implemented with less time and high fidelity. Therefore, the scheme provides a promising way for robust on‐chip converting of low‐frequency electrical signal into much higher‐frequency optical signal, and thus enabling large‐scale quantum information networks to grow in size and complexity.     

Entangled W State Generation via Adiabatic Passage in Cavity QED

A scheme is proposed to generate W state of N atoms trapped in a cavity, based on adiabatic passage along dark state. Taking advantage of adiabaticpassage, the atoms have no probability of being excited and thus the atomicspontaneous emission is suppressed. The scheme is simple. It does not needto adjust the interaction time accurately, and does not need to prepare thecavity field in one-photon state. Numerical simulation shows that thesuccessful probability of the scheme increases with the increasing of the atom number.     

Quantum State Transfer via Parity Measurement

We propose two schemes for quantum state transfer using parity measurement in a cavity-waveguide system, and the two schemes can be generalized to multidipole’s case. An important advantage is that quantum state transfer can be completed by single-qubit rotations and the measurement of parity. Therefore, our scheme can be realized in the scope of current experimental technology.     

Three-Dimensional Quantum State Transferring Between Two Remote Atoms by Adiabatic Passage under Dissipation

Recently, Zhou et al. [Phys. Rev. A 79 (2009) 044304]proposed a scheme for transferring three-dimensional quantum statesbetween remote atomic qubits confined in cavities connected byfibers through adiabatic passage. In order to avoid the decoherencedue to spontaneous emission, Zhou et al. utilized the large detuningatom-field interaction. In the present paper, we discuss theinfluence of dissipation on the scheme in both the resonantatom-field interaction case and the large detuning case. Wenumerically analyze the success probability and the transferringfidelity. It is shown that the resonant case is a preferable choicefor the technique of the stimulated Raman adiabatic passage (STIRAP)due to the shorter operation time and the smaller probability of dissipation.     

Three-Dimensional Quantum State Transferring Between Two Remote Atoms by Adiabatic Passage under Dissipation

Recently, Zhou et al. [Phys. Rev. A 79 （2009） 044304] proposed a scheme for transferring three-dimensional quantum states between remote atomic qubits confined in cavities connected by fibers through adiabatic passage. In order to avoid the decoherence due to spontaneous emission, Zhou et al. utilized the large detuning atom-field interaction. In the present paper, we discuss the influence of dissipation on the scheme in both the resonant atom-field interaction case and the large detuning case. We numerically analyze the success probability and the transferring fidelity. It is shown that the resonant case is a preferable choice for the technique of the stimulated Raman adiabatic passage （STIRAP） due to the shorter operation time and the smaller probability of dissipation.     

Preparation of W State with Superconducting Quantum-Interference Devices in a Cavity via Adiabatic Passage

We propose an alternative scheme to prepare W state by using superconducting quantum-interference devices （SQUIDs） coupled to a largely-detuned cavity. The present scheme is based on evolution by adiabatic passage, where only by tuning adiabatically the Rabi frequencies of the classical microwave pulses we can obtain the standard W state without measurement or any auxiliary SQUIDs. Thus the procedure is simplified and the scheme can be achieved with very high success probability since the errors in dynamical or geometric ways can be avoided. In addition, the SQUID system and the cavity have no probability of being excited state. Thus decoherence caused by the excited-level spontaneous emission or the cavity decay is suppressed.     

Stark-Chirped Rapid Adiabatic Passage in Presence of Dissipation for Quantum Computation

Stark-chirped rapid adiabatic passage （SCRAP） is an important technique used for coherent quantum controls. In this paper we investigate how the practically-existing dissipation of the system influences on the efficiency of the passage, and thus the fidelities of the SCRAP-based quantum gates. With flux-biased Josephson qubits as a specifical example, our results show clearly that the efficiency of the logic gates implemented by SCRAP are robust against the weak dissipation. The influence due to the non-adiabtic transitions between the adiabatic passages is comparatively significantly small. Therefore, the SCRAP-based logic gates should be feasible for the realistic physical systems with noises.     

Generation and Transfer of Quantum Entangled State via Spin-Parity Measurements

We propose two schemes for entanglement generation and quantum state transfer via a double-quantum-dot system. Our schemes only need spin-parity measurements and single-qubit measurements combined with additional qubits. Discussions about the feasibility of the current scheme show that they would be realized within the current experimental technology.     

Entanglement and Phase-Covariant Cloning for Multiple Trapped Ions via Adiabatic Passage

We describe a scheme for the generation of W states and implementation of phase-covariant cloning for n trapped ions. The scheme does not use the vibational mode as the memory and works beyond the Lamb-Dicke regime. The procedure is robust against moderate fluctuations of experimental parameters by using adiabatic passage.     

Quantum State Transfer Between Any Pair of Qubits in a Quantum Network via Optical Fibers

We propose scheme for transferring quantum state between any pair of nodes in a quantum network. Each node consists of an atom and a cavity, with the atom acting as the quantum bit. Any two adjacent nodes are connected by an optical fiber. During the operation neither the atomic system nor the fibers are excited, which is important in view of decoherence. Under certain conditions, the probability that the cavities are excited is negligible. The method has an inherent robustness against the fluctuation perturbations in the classical control parameters and the randomness in the atomic position. The scheme can be generalized to implement quantum phase gate between any two remote qubits.     

Scalable Implementation of Multi-qubit Quantum Grover Search with Atomic Ensembles by Adiabatic Passage

We propose a simple scheme to implement multi-qubit quantum Grover search with atomic ensembles by adiabatic passage. The scheme is immune to the atomic spontaneous emission, cavity decay and fiber decay. Furthermore, the process can be speeded up with atomic ensemble instead of single atom, which is important in view of decoherence. With each atomic ensemble confined in an individual cavity, our scheme is experimentally scalable to multi-qubit cases.