Implementation of quantum phase gate between two atoms via Rydberg antiblockade and adiabatic passage

Combining adiabatic passage and Rydberg antiblockade, we propose a scheme to implement a two-qubit phase gate between two Rydberg atoms. Detuning parameters between frequencies of atomic transitions and those of the corresponding driving lasers are carefully chosen to offset the blockade effect of two Rydberg atoms, so that an effective Hamiltonian,representing a single-photon detuning L-type three-level system and concluding the quantum state of two Rydberg atoms excited simultaneously, is obtained. The adiabatic-passage technique, based on the effective Hamiltonian, is adopted to implement a two-atom phase gate by using two time-dependent Rabi frequencies. Numerical simulations indicate that a high-fidelity two-qubit p-phase gate is constructed and its operation time does not have to be controlled accurately. Besides,owing to the long coherence time of the Rydberg state, the phase gate is robust against atomic spontaneous emission.

A scheme of quantum phase gate for trapped ion

We propose a scheme to implement two-qubit controlled quantum phase gate（CQPG） via a single trapped two-level ion located in the standing wave field of a quantum cavlty, in which the trap works beyond the Lamb--Dicke limit. When the light field is resonant with the atomic transition ｜g） →← ｜e） of the ion located at the antinode of the standing wave, we can perform CQPG between the internal and external states of the trapped ion; while the frequency of the light field is chosen to be resonant with the first red sideband of the collective vibrational mode of the ion located at the node of the standing wave, we can perform CQPG between the cavity mode and the collective vibrational mode of the trapped ion. Neither the Lamb--Dicke approximation nor the assistant classical laser is needed. Also we can generate a GHZ state if assisted with a classical laser.

One-Step Scheme for Realizing N-Qubit Quantum Phase Gates with Hot Trapped Ions

一个计划为与套住的离子认识到一扇 N-qubit 量阶段门被介绍。利用震动的模式的虚拟刺激， qubit 系统经历一在选择对称的 Dicke subspace 的 Rabi 摆动完整周期。计划仅仅包含一个单个步骤，操作对热运动感觉迟钝。而且，计划不要求离子的单个探讨。

Quantum logic gates with two-level trapped ions beyond Lamb-Dicke limit

In the system with two two-level ions confined in a linear trap, this paper presents a simple scheme to realize the quantum phase gate （QPG） and the swap gate beyond the Lamb Dicke （LD） limit. These two-qubit quantum logic gates only involve the internal states of two trapped ions. The scheme does not use the vibrational mode as the data bus and only requires a single resonant interaction of the ions with the lasers. Neither the LD approximation nor the auxiliary atomic level is needed in the proposed scheme. Thus the scheme is simple and the interaction time is very short, which is important in view of decoherence. The experimental feasibility for achieving this scheme is also discussed.

Generation of unconventional geometric phase gates in ion trap-optical cavity system by squeezed operators

Based on squeezed operators this paper has implemented an ideal unconventional geometric quantum gate （GQG） in ion trap-optical cavity system by radiating the trapped ions with the cavity field of frequency ωc and an external laser field of frequency ωL. It can ensure that the gate time is shorter than the coherence time for qubits and the decay time of the optical cavity by appropriately tuning the ionic transition frequency ω0, the frequencies of the cavity mode ωc and the vibrational mode v. It has also realized the unconventional GQG under the influence of the cavity decay based on the squeezed-like operators and found that the present scheme works well for the smaller cavity decay by investigating the corresponding fidelity and success probability.

实现三比特量子控制相位门的离子阱方案(英文)

提出了一个利用离子阱系统实现三比特量子控制相位门的方案。在这个方案里,只需对囚禁离子辅以单比特旋转操作并与激光发生共振相互作用便可实现三比特控制相位门。相比其他文献中控制相位门的实现方案,此方案的优势在于所用的步骤更为简便易行。另外,此方案不需要任何测量。

基于频率调制激光驱动的囚禁离子几何相位逻辑门

为了避免激光相位的起伏对几何相位逻辑门保真度的影响,提出一种基于囚禁离子的量子几何相位逻辑门的新方案.该方案是利用一束频率调制的行波激光场作用于两个囚禁离子上实现的.它的优点有:操作简单,仅需一步就能实现,不灵敏于激光场的相位也不需要对囚禁离子进行个别寻址.

热囚禁离子系统中的两量子比特条件相位门的简单方案

提出了一个实现两离子量子逻辑门的简单方案。本方案使用了两个囚禁于线性阱的三能级离子。本方案不使用振动模作为数据总线,仅需要激光与离子的单个相互作用,因而相互作用时间变短,这点从退相干的角度看是很重要的,而且本方案对振动模的加热不敏感。

基于绝热演化通道的任意比特对称Dicke态的制备

根据绝热通道技术及暗态的演化机制,提出多个囚禁离子量子比特的纠缠Dicke态制备方案.该方案实现了处于激发状态的离子数连续可调,可完成任意对称Dicke态的制备.离子阱系统处于暗态,且能按照量子绝热演化进行,对试验参数的涨落不敏感.离子阱系统具有良好的屏蔽性,使离子几乎不受外界环境的影响,对离子比特的量子操作有更高的保真度.

几何量子计算

实现可集成的量子计算的关键步骤是实现保真度足够高的一组普适量子逻辑门 .最近几年发展的几何量子计算使用几何位相来实现量子逻辑门 ,其特点是利用几何位相的整体几何性质来避免某些局域的无规噪声的影响 ,从而实现较高保真度的量子门 .文章先简要介绍常规几何量子逻辑门的概念 ,然后重点介绍最近提出的非常规几何量子计算 :量子计算中使用的逻辑门的总位相既包含有几何位相 ,又包含有动力学位相 ,但它仅依赖于一些几何特征 .而且 ,对于任意的量子位输入态 ,在量子门操作过程中积累的位相要么是零 ,要么是仅依赖几何特征的位相 .