Remote atomic information concentration without Bell-state measurement

This paper proposes a scheme for information concentration of two remote two-level atoms in cavity QED. This scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is large-detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. This idea can directly be generalized in the case of multi-atom information concentration.     

Scheme for implementing an economical phase-covariant quantum cloning machine of distant atomic qubits with single-photon interference

By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of distributed quantum information processing.     

Universal quantum gates between distant quantum dot spins

We propose a scheme to engineer a nonlocal two-qubit phase gate between two remote quantum-dot spins in cavities. As the effect of cavity decay is considered and strong coupling condition is not used, the scheme has good adaptability. Along with single qubit operations, one can perform in principle various types of distributed quantum information processing.     

High efficient scheme for remote state preparation with cavity QED

In this paper, a scheme is proposed for remote state preparation （RSP） with cavity quantum electrodynamics （QED）. In our scheme, two observers share two-atom nonmaximally entangled state as quantum channels and can realize remote preparation of state of an atom. We also propose a generalization for remote preparation of N-atom entangled state by （N＋1）-atom GHZ-like state （N ≥ 2）. By this scheme, one single-atom projective measurement is enough for the RSP of a qubit or N-atom entangled state, and the probability of success for RSP is unity. Furthermore, we have considered the case where observers use W-like state as quantum channels to realize RSP of a qubit. We compare our scheme with existing ones.     

基于低Q腔光子Faraday旋转的远程态制备

基于低Q腔中单光子的输入与输出关系,提出了利用偏振光Faraday旋转分别遥远制备单原子态和两原子纠缠态的可行方案.研究结果表明,当初始原子态的系数为实数时,通过选择合适的偏振光、腔场与原子相互作用系统的参数,单原子态与两原子纠缠态的远程制备均可确定性地得以实现.与以前的原子态远程制备方案相比,本文方案采用光子作为飞行比特来传递量子信息,故原则上可实现原子态的真正长距离制备.由于原子态的信息编码在耗散单边腔囚禁的Λ型三能级原子的两个基态能级,且原子仅虚激发,因此本文方案对腔衰减和原子自发辐射不敏感.此外,本文所提出的两种方案不需要两体或多体正交测量,仅涉及单体直积态测量,而且两种方案都工作在低Q腔,不需要原子与光腔的强耦合,从而有效降低了实验难度.     

Generation of Cluster States in Cavity QED

We propose two schemes for the generation of cluster states in the context of cavity quantum electrodynamics （QED）. In the first scheme, we prepare multi-cavity cluster states with information encoded in the coherent states. The second scheme is to generate multi-atom cluster states, where qubits axe represented by the states of cascade Rydberg atoms. Both the schemes axe based on the atom-cavity interaction and the atomic spontaneous radiation can be efficiently reduced since the cavity frequency is largely detuned from the atomic transition frequency.     

Quantum Teleportation of the Two-Qubit Entangled State by Use of Four-Qubit Entangled State

In this article, a scheme for quantum teleportation of a two-qubit entangled state using four-qubit cluster state is discussed by use of cavity quantum electrodynamics (QED) involving the interaction of the atoms with the cavity. In this protocol, by using a one-dimensional maximally four-qubit cluster state as quantum channel, quantum information of an unknown state of two two-level particles is faithfully transmitted from a sender (Alice) to a remote receiver (Bob). According to the results measured by the Bob, as it is shown, the unknown two-particle entangled state can be teleported perfectly, and the successful possibilities and fidelities of the scheme can reach 1.0.     

A Scheme for Generating Cluster States via Raman Interaction

A scheme for generating cluster states via Raman interaction is proposed. In the scheme, we firstly prepare cluster states of multi-cavities with information encoded in the coherent states and then generate cluster states of multiatoms, which encode the information in the ground states of A-type atoms. The advantages of our scheme are that the atomic spontaneous radiation can be efficiently reduced since the cavity frequency is largely detuned from the atomic transition frequency and the Hadamard gate operation of the coherent states is replaced by measuring the coherent states.     

Teleportation of a Superposition of Three Orthogonal States of an Atom via Photon Interference

We propose a scheme to teleport a superposition of three states of an atom trapped in a cavity to a second atom trapped in a remote cavity. The scheme is based on the detection of photons leaking from the cavities after the atom-cavity interaction.     

Teleportation of a Superposition of Three Orthogonal States of an Atom via Photon Interference

We propose a scheme to teleport a superposition of three states of an atom trapped in a cavity to a second atom trapped in a remote cavity. The scheme is based on the detection of photons leaking from the cavities after the atom-cavity interaction.     

Remote entanglement for quantum networks

Quantum networks are distributed many-body quantum systems with tailored topology and controlled information exchange. We present two schemes to generate remote entanglement, in atomic external degrees of freedom and between cavities. In the first scheme, we entangle two atoms with their cavities in momentum space through Bragg diffraction. Thereafter, in order to trace out the cavities, we let resonantly interact an auxiliary atom with each cavity. In the last, we perform quantum measurement on two auxiliary atoms and get remote entangled state in atomic external degrees of freedom. In the second scheme, we have a three cavities system. The other two cavities, A and B, are entangled with indistinguishable modes of cavity, C. Performing quantum measurement on third cavity, C, we disentangle it from the system and the cavities, A and B, become entangled.     

Scheme for implementing frequency up-conversion between two collective atomic modes

This paper presents a scheme for realizing the frequency up-conversion between two collective atomic modes. In the scheme two atomic samples are coupled to a cavity mode. Under the large detuning condition, the two collective atomic modes are coupled via the virtual excitation of the cavity mode and the effective Hamiltonian corresponds to the frequency up-conversion. In the scheme the cavity mode is only virtually excited and thus the process is insensitive to cavity decay.     

远程制备双原子纠缠态

提出一种远程制备双原子纠缠态的方案,该方案基于两个原子与单模腔场的同时非共振相互作用.由于双粒子纠缠态比三粒子纠缠态容易制备,方案用两对双原子纠缠态作为量子通道.Alice 拥有的两个相同原子同时与一单模腔场非共振相互作用.Alice已知她要制备的纠缠态,她选择适当的相互作用时间、测量她所拥有的两个原子并通过经典通道通知Bob.Bob引入一个相同的辅助原子和一个单模腔场来实现方案.方案对腔场状态和腔损耗不敏感,基于当前的腔QED 技术,方案能在实验上实现.该方案有望在量子信息过程中有重要的应用价值.     

Deterministic Remote Entangled State Preparation Using Cluster State in Cavity QED

We propose a scheme to prepare a two-qubit remote entangled state based on four-qubit cluster state in cavity quantum electrodynamics which involves the interaction of the atoms with the cavity. Through using four-particle cluster state as a quantum channel, we shown that the probability and fidelity of the successful remote state preparation can approach unit. In addition, our protocol only need single qubit measurement instead of the conventional Bell-state measurement, then it is quite simple but also very robust to the cavity decay and the influence of the thermal field.     

Remote Preparation of an Arbitrary Two-atom State in the Cavity QED

A simple scheme for remote preparation of an arbitrary two-atom state in the cavity QED. An arbitrary two-atom entangled state can be prepared perfectly. Our protocol only need single qubit measurement instead of the conventional Bell-state measurement, then it is quite simple but also very robust to the cavity decay and the influence of the thermal field. The probability of the success in our scheme is 1.0.     

Remote Quantum Information Concentration Via Weak Cross-Kerr Nonlinearity

By utilizing the quantum parity-check detectors (PCDs) based on the weak cross-Kerr nonlinearities, we propose a scheme for realizing the remote quantum information concentration (RQIC) with the quantum channel of four-photon bound entangled state. After the PCDs and single-photon operations, quantum information initially distributed in three spatially separated photons is concentrated back to a single photon without performing any global operations. The success probability of the scheme is almost a unit. The necessary single-photon unitary operations corresponding to possible measurement outcomes are given detailedly.     

Optimal remote state preparation

We prove that it is possible to remotely prepare an ensemble of noncommuting mixed states using communication equal to the Holevo information for this ensemble. This remote preparation scheme may be used to convert between different ensembles of mixed states in an asymptotically lossless way, analogous to concentration and dilution for entanglement.     

利用双光子过程耦合腔系统实现量子信息转移

给出了利用两个二能级原子和耦合腔双光子过程相互作用系统实现量子信息转移的方案。该方案中二能级原子通过双光子跃迁与单模腔场发生共振相互作用。通过控制原子与光场的相互作用时间,实现量子信息从一个原子转移到另一个原子。     

Simultaneous remote monitoring of atmospheric methane and water vapor using an integrated path DIAL instrument based on a widely tunable optical parametric source

We report on the remote sensing capability of an integrated path differential absorption lidar (IPDIAL) instrument, for multi-species gas detection and monitoring in the 3.3–3.7 µm range. This instrument is based on an optical parametric source composed of a master oscillator-power amplifier scheme—whose core building block is a nested cavity optical parametric oscillator—emitting up to 10 µJ at 3.3 µm. Optical pumping is realized with an innovative single-frequency, 2-kHz repetition rate, nanosecond microchip laser, amplified up to 200 µJ per pulse in a single-crystal fiber amplifier. Simultaneous monitoring of mean atmospheric water vapor and methane concentrations was performed over several days by use of a topographic target, and water vapor concentration measurements show good agreement compared with an in situ hygrometer measurement. Performances of the IPDIAL instrument are assessed in terms of concentration measurement uncertainties and maximum remote achievable range.     

Generation of a Five-Atom Cluster State in Cavity QED

We present a scheme for the generation of a five-atom cluster state in cavity QED. During the preparation no quantum information is transferred from the atoms to the cavity, and thus the scheme is insensitive to the cavity field states and cavity decay.