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One-step implementation of an N-qubit quantum phase gate through a double Raman passage

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Chinese Physics B 2010年第3期19卷 330-333页

作者：吕海燕於亚飞张智明 Laboratory of Photonic Information Technology SIPSE & LQITSouth China Normal University

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.

关键词： Raman-coupled model quantum computation quantum phase gate

A scheme for conditional quantum phase gate via bimodal cavity and a∧-type three-level atom

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Chinese Physics B 2006年第11期15卷 2518-2522页

作者：蔡建武方卯发廖湘平郑小娟 College of Physics and Information Science Hunan Normal University Changsha 410081 China Department of Physics Science and Electronics Zhuzhou Teacher' College Zhuzhou 412007 China

We propose a scheme to implement a two-qubit conditional quantum phase gate for the intracavity field via a single three-level ∧-type atom driven by two modes in a high-Q cavity. The quantum inforraation is encoded o... 详细信息

关键词： quantum phase gate ∧-type three-level atom bimodal cavity fidelity

A scheme of quantum phase gate for trapped ion

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Chinese Physics B 2007年第6期16卷 1566-1569页

作者：蔡建武方卯发郑小娟廖湘萍 College of Physics and Information Science Hunan Normal University Changsha 410081 China Department of Physics Science and electronics Zhazhou Teacher's College Zhuzhou 412007 China School of Physics Science and Technology Central South University Changsha 410082 China

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.

关键词： quantum phase gate single trapped ion single quantum cavity mode GHZ state

Generation of an N -qubit phase gate via atom–cavity nonidentical coupling

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Chinese Physics B 2009年第11期18卷 4683-4689页

作者：张英俏张寿 Centre for the Condensed-Matter Science and Technology Harbin Institute of Technology Department of Physics College of ScienceYanbian University

A scheme for approximate generation of an N-qubit phase gate is proposed in cavity QED based on nonidentical coupling between the atoms and the cavity. The atoms interact with a highly detuned cavity-field mode, but quantum information does not transfer between the atoms and cavity field, and thus the cavity decay is negligible. The gate time does not rise with an increase in the number of qubits. With the choice of a smaller odd number l （related to atom-cavity coupling constants）, the phase gate can be generated with a higher fidelity and a higher success probability in a shorter time （the gate time is much shorter than the atomic radiative lifetime and photon lifetime）. When the number of qubits N exceeds certain small values, the fidelity and success probability rise slowly with an increase in the number of qubits N. When N→∞, the fidelity and success probability infinitely approach 1, but never exceed 1.

关键词： quantum phase gate three-level atom cavity QED

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

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Chinese Physics B 2009年第4期18卷 1352-1356页

作者：郑小娟罗益民蔡建武 School of Material Science and Engineering Central South University School of Physics Science and Technology Central South University Department of Physics Hunan Industrial University

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.

关键词： trapped ions quantum phase gate swap gate beyond the Lamb Dicke limit

Creating unconventional geometric phase gate using squeeze-like operator assisted by strong driving field

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Chinese Physics B 2007年第6期16卷 1559-1565页

作者：朱爱东张寿 Yeon Kyu-Hwang Yu Seong-Cho Um Chung-In Center for the Condensed-Matter Science and Technology Harbin Institute of Technology Harbin 150001 China Department of Physics College of Science Yanbian University Yanji 133002 China Department of Physics & BK21 Program for Device Physics College of Natural Science Chungbuk National University Cheonju Chungbuk 361-763 Republic of Korea Department of Physics College of Science Korea University Seoul 136-701 Republic of Korea

Based on the idea that a squeezing process can be thought of as a total cumulative effect of a large number of tiny squeezing processes, we define a squeeze-like operator with a time-dependent squeeze parameter. Applying this operator to and combining with a system which includes a two-photon interaction between two atoms and an initial vacuum cavity field, and resorting to a resonant strong driving classical field, we obtain an unconventional geometric phase gate with a shorter gating time.

关键词： squeeze-like operator quantum phase gate strong driving field