阶梯型三能级原子-腔耦合系统中Fock态的产生

探讨了阶梯形三能级原子 腔耦合系统中由绝热跟随技术引起的光子Fock态的产生 .结果发现 :对于单模腔QED系统 ,通过受激拉曼绝热跟随技术 ,在微波区域内可实现单光子Fock态的制备 ;对于双模腔QED系统 ,通过斯塔克移动的快绝热跟随技术可实现双光子对Fock态的产生.The behavior of an atom-cavity system using a three-level ladder atom was investigated. It is found that, for one-mode cavity QED, a single photon can be generated via the technique of stimulated Raman adiabatic passage; for two-mode cavity QED, a two-photon pair can be generated via Stark-shift rapid adiabatic passage.     

Superposition of Fock states via adiabatic passage in a coupled four-level atom－cavity system

We have investigated the behaviour of an atom－cavity system via a stimulated Raman adiabatic passage technique in a four-level system, in which two dark states are present. We find, because of the coherent control field, that a superposition of Fock states can be prepared, even when the cavity is initially not in its vacuum state. This method provides a way to generate arbitrary quantum states of a cavity field.     

Acoustic topological adiabatic passage via a level crossing

Stimulated adiabatic passage has been extensively studied to achieve robust and selective population transfer in quantum systems. Recently, the quantum-classic analogy has been rapidly developing and can be considered responsible for the implementation of the adiabatic transfer of sound energy in cavity chain systems. In this article, we investigate the adiabatic transfer of sound energy between two topological end states in the Su-Schrieffer-Heeger(SSH) cavity chain, which can be considered to be the acoustic analog of the quantum chirped-pulse excitation. The topological adiabatic passage in SSH cavity chain has two categories. When the single-cavity resonance frequencies on the sublattices A and B in the SSH cavity chain do not switch their spectrum positions, the topologically protected adiabatic evolution results in the returning passage of the sound excited in one end cavity. When a level crossing with single-cavity resonance frequencies on the sublattices A and B exhibits switch in the frequency spectrum, acoustic energy is observed to be topologically pumped between the two end cavities of the SSH chain.     

基于绝热捷径快速实现远距离的四维纠缠态的制备

作为量子信息处理的载体,量子纠缠态一直以来都是量子信息领域的研究热点.相比于低维纠缠态,高维纠缠态使得量子通信具有更快的传输速度、更强的安全性、更高的噪声容忍阈值等特点.另外,绝热技术因其对实验参数起伏不敏感而被广泛应用于纠缠态的制备,然而绝热过程需要相当长的演化时间,因此绝热捷径应运而生.本文提出了一种采用无跃迁量子驱动构建绝热捷径实现快速制备两个原子的四维纠缠态的理论方案,该系统中的两个原子分别被囚禁在两个由光纤连接的双模腔中.为了获得一个技术上可操作的物理系统,本方案采用能级失谐设计出一个可精确驱动系统沿着某一个系统的瞬时本征态演化的哈密顿.该方案所采用的无跃迁量子驱动构建绝热捷径不仅大大缩短了演化时间,而且在实验上也比较容易实现.本文还数值模拟了消相干因素对四维纠缠态保真度的影响,结果表明,只要脉冲参数选取在一定范围内,光纤耗散、腔场耗散和原子自发辐射等不利因素都会被大大抑制.     

Simple scheme for direct measurement of exponential phase moments of cavity fields by adiabatic passage

We propose simple experimental scheme for direct measurement of the exponential phase moments of single-mode cavity field. The scheme is based on the adiabatic passage technique, and all the relevant quantities can be obtained directly from the measurement of atomic populations. We also point out that scheme can be used to measure Q-function of single-mode cavity fields and verify the phase-number uncertainty relation.     

Creation of atomic W state in a cavity by adiabatic passage

We propose two relatively robust schemes to generate controllable (deterministic) atomic W states of three Λ-like atoms interacting with an optical cavity and a laser beam. Losses due to atomic spontaneous emissions and to cavity decay are efficiently suppressed by employing adiabatic passage technique and appropriately designed atom-field couplings. In these schemes the three atoms traverse the cavity-mode and the laser beam and become entangled in the free space outside the cavity.     

Vacuum-stimulated raman scattering based on adiabatic passage in a high-finesse optical cavity

We report on the first observation of stimulated Raman scattering from a Lambda-type three-level atom, where the stimulation is realized by the vacuum field of a high-finesse optical cavity. The scheme produces one intracavity photon by means of an adiabatic passage technique based on a counterintuitive interaction sequence between pump laser and cavity field. This photon leaves the cavity through the less-reflecting mirror. The emission rate shows a characteristic dependence on the cavity and pump detuning, and the observed spectra have a subnatural linewidth. The results are in excellent agreement with numerical simulations.     

Generation of atomic entangled states in a bi-mode cavity via adiabatic passage

We propose schemes to prepare atomic entangled states in a bi-mode cavity via stimulated Raman adiabatic passage (STIRAP) and fractional stimulated Raman adiabatic passage (f-STIRAP) techniques. Our scheme should be realizable in the near future because of the existence of all experimental ingredients. Our numerical simulation shows we can entangle the atoms with high fidelities by choosing proper laser pulses.     

Quantum state engineering in a cavity by Stark chirped rapid adiabatic passage

We propose a robust scheme to generate single-photon Fock states and atom–photon and atom–atom entanglement in atom–cavity systems. We also present a scheme for quantum networking between two cavity nodes using an atomic channel. The mechanism is based on Stark-chirped rapid adiabatic passage (SCRAP) and half-SCRAP processes in a microwave cavity. The engineering of these states depends on the design of the adiabatic dynamics through the static and dynamic Stark shifts.     

Multiphonon-resonance quantum Rabi model and adiabatic passage in a cavity-optomechanical system

In this paper,we propose a scheme to achieve a multiphonon-resonance quantum Rabi model and adiabatic passage in a strong-coupling cavity optomechanical system.In the scheme,when the driving bichromatic laser beam is adjusted to the off-resonant j-order red-and blue-sideband,the interaction between the cavity and mechanical oscillator leads to a j-phonon resonance quantum Rabi model.Moreover,we show that there exists a resonant multi-phonon coupling via intermediate states connected by counter-rotating processes when the frequency of the simulated bosonic mode is near a fraction of the transition frequency of the simulated two-level system.As a typical example,we theoretically analyze the two-phonon resonance quantum Rabi model,and derive an effective Hamiltonian of the six-phonon coupling.Finally,we present a method of six-phonon generation based on adiabatic passage across the resonance.Numerical simulations confirm the validity of the proposed scheme.Theoretically,the proposed scheme can be extended to the realization of 3j-phonon state.     

基于超绝热捷径技术快速制备超导三量子比特Greenberger-Horne-Zeilinger态

本文提出了一个基于超绝热捷径技术快速制备超导三量子比特Greenberger-Horne-Zeilinger态的理论方案.该方案首先在量子Zeno动力学的帮助下得到系统的有效哈密顿量,之后通过引入与有效哈密顿量具有相同形式的反向导热哈密顿量来构建绝热捷径,加速了整个系统的演化过程.该方案不需要初态和目标态之间的直接耦合,在实验上也更容易实现.数值模拟结果表明该方案对超导量子比特的自发辐射、波导谐振腔的泄漏以及超导量子比特的退相位是鲁棒的.     

复合绝热通道技术在谐相互作用调制的Landau-Zener模型中的应用

将复合绝热通道技术应用于谐相互作用调制的Landau-Zener模型, 研究了调制频率和耦合强度在不同的参量条件下系统的跃迁概率, 发现这种方法能够有效抑制跃迁概率的非绝热振荡, 可以在很大的参数范围内使布居数完全反转, 实现超高保真度,将系统的误差降低到10^-4以下. 关键词： 复合绝热通道技术 Landau-Zener模型 跃迁概率     

Entanglement of Momentum for a Single Photon with a Single Atom

In this talk, the interaction of a single photon injected to a single atom is studied, for which initially the photon is uncorrelated with the atom. The spontaneous emitted photon will then evolve to be entangled with the atom on their continuous kinetic variables （momentum） in the process of resonant scattering. We find the relations between the entanglement and their physical control parameters （such as the linewidth of the injected photon wave packet, and that of the atomic wave packet, etc. ）, which indicates that high entanglement can be reached by broadening the scale of the atomic wave or squeezing the linewidth of the incident single-photon pulse.     

One-step generation of four-dimensional entanglement via adiabatic passage in cavity quantum electrodynamics

A scheme is proposed for generating a four-dimensional entangled state for two atoms trapped in a cavity by one step via adiabatic passage. The scheme does not need the exact control of the experimental parameters and the evolution time. Its predominant decohence factor depends on the magnitude of classical Rabi frequencies, therefore, there exists a reasonable value range of Rabi frequencies of the classical fields. Numerical simulation indicates that the excited probabilities of the atoms and the cavity modes are very small, so the scheme is very robust against decoherence. The four-dimensional entanglement can be generated with a high fidelity with present technique.     

Preparation of Fock states and quantum entanglement via stimulated Raman adiabatic passage using a four-level atom

We study the behaviour of an atom-cavity system exposed to a stimulated Raman adiabatic passage (STIRAP) process in a four-level system, with a coupling scheme which generate two degenerate dark states. We find that the non-adiabatic interaction of the two dark states guarantees that the cavity Fock states can always be generated by both intuitively and counterintuitively ordered pulses. Furthermore, we propose a method to entangle two atoms. Depending on the ordering of the pulses two orthogonal entangled states can be prepared. Since these entangled states do not have component of the excited states included, the technique is robust against the detrimental consequences of spontaneous emission. Received 20 March 2001     

Efficient Scheme for One-Way Quantum Computing with Radiofrequency SQUID Qubits byAdiabatic Passage

We proposed an efficient scheme for constructing a quantum controlled phase-shift gate and generating the cluster states with rf superconducting quantum interference devices (SQUIDs) coupled to a microwave cavity through adiabatic evolution of dark eigenstates. During the operation, the spontaneous emission is suppressed since the rf SQUIDs are always in the three lowest flux states. Considering the influence from the cavity decay with achievable
experimental parameters, we numerically analyze the success probability and the fidelity for generating the two-SQUID maximally entangled state and the controlled phase-shift gate by adiabatic passage.     

Creation of entangled W states of four two-level atoms in a cavity via quadrapod adiabatic passage

In this paper, we considered four two-level atoms coupled with a microwave cavity via stimulated Raman adiabatic passage in quadrapod linkage pattern. Engineering Rabi frequencies of a system with suitable pulse orders, results in entangled W states of four atoms. We also compared the theoretical results with the numerical solutions of the Schrödinger equation in the adiabatic limit which shows the creation of W states at the end of dynamics.     

Robust generation of qutrit entanglement via adiabatic passage of dark states

We propose a scheme for the deterministic generation of qutrit entanglement for two atoms trapped in an optical cavity. Taking advantage of the adiabatic passage, the operation is immune to atomic spontaneous emission as the atomic excited states are never populated; under certain conditions, the probability that the cavity is excited is negligible. We also study the influences of the dissipation due to the atomic spontaneous emission and cavity decay.     

Implementation of quantum search scheme by adiabatic passage in a cavity--laser--atom system

This paper proposes a scheme for implementing the adiabatic quantum search algorithm of different marked items in an unsorted list of N items with atoms in a cavity driven by lasers. N identical three-level atoms are trapped in a single-mode cavity. Each atom is driven by a set of three pulsed laser fields. In each atom, the same level represents a database entry. Two of the atoms are marked differently. The marked atom has an energy gap between its two ground states. The two different marked states can be sought out respectively starting from an initial entangled state by controlling the ratio of three pulse amplitudes. Moreover, the mechanism, based on adiabatic passage, constitutes a decoherence-free method in the sense that spontaneous emission and cavity damping are avoided since the dynamics follows the dark state. Furthermore, this paper extends the algorithm with m (m>2) atoms marked in an ideal situation. Any different marked state can be sought out.     

通过绝热过程实现任意一原子态的隐形传态(英文)

我们利用腔场和激光相互作用,提出一个冗余的、对消相干不敏感的方案,来传输任意一个三能级原子的态.由于原子自发跃迁和腔延迟作用会造成信息丢失,通过用部分绝热过程和适当的原子场耦合的设计,信息丢失能够被有效的抑制,此方案传送成功的几率是0.5,保真度是1.