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Alternating Current Zeeman and Stark Interference Effect in Ramsey Separated Oscillating Fields

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Chinese Physics Letters 2001年第2期18卷 202-204页

作者： CHEN Jing-Biao WANG Feng-Zhi YANG Dong-Hai WANG Yi-Qiu Department of Electronics and Key Laboratory for Quantum Information and Measurements of Education MinistryPeking UniversityBeijing 100871

Analytic expressions have been derived of the alternating current(ac)Zeeman and ac Stark effect in an atomic beam magnetic resonance method using Ramsey separated oscillating *** interesting feature which will affect the normal Ramsey pattern is that an interference fringe is superimposed on the dispersion lineshapes of the normal ac Zeeman or ac Stark *** point out that this new character of ac Zeeman(ac Stark)effect generally exists in all kinds of Ramsey method,for example,in the optical Ramsey atomic interferometer and atomic beam frequency *** important implication is that,particularly in an atomic beam frequency standard using Ramsey method,this effect has an influence on the evaluation of the second-order Doppler frequency shift.

关键词： effect Ramsey Zeeman

Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard

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Chinese Physics Letters 2006年第12期23卷 3198-3201页

作者：黄凯凯张建伟于得水陈振辉庄伟陈景标 key laboratory for quantum information and measurements of Ministry of Education School of Electronics Engineering and Computer Science Peking University Beijing 100871

A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave dock, like the 5071 Cs clock （from Hp to Agilent, now Symmetricom company）, both in accuracy and stability.

关键词： SHARP ANGLE INCIDENCE PROBING LASER-BEAM SPECTROSCOPY ATOMS CLOCK

Absence of State Collapse and Revival in a Superconducting Charge Qubit

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Communications in Theoretical Physics 2007年第12期48卷 1029-1032页

作者： HUO Wen-Yi~1 and LONG Gui-Lu~(1,2,3)~1 Department of Physics amd key laboratory for quantum information and measurements,Tsinghua University,Beijing100084,China~2 key laboratory for Atomic and Molecular Nanosciences,Tsinghua University,Beijing 100084,China~3 National laboratory for information Science and Technology,Hsinghua University,Beijing 100084,China Department of Physics amd key laboratory for quantum information and measurements Tsinghua University key laboratory for Atomic and Molecular Nanosciences Tsinghua University National laboratory for information Science and Technology Hsinghua Univers

The Hamiltonian of a superconducting charge qubit with a configuration of dc SQUID contains an interac-tion between the LC oscillator part and charge *** interaction may leads to quantum state collapse and revivalwhich degrades the charge qubits and leads to serious *** analysis shows that the existing charge qubitparameters do not lead to this phenomenon,which is very good for the superconducting charge

关键词： quantum computer superconducting charge qubit absence and revival

Measuring-basis-encrypted six-state quantum key distribution scheme

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Progress in Natural Science:Materials International 2006年第1期16卷 84-89页

作者： CHEN Pan1, DENG Fuguo1, WANG Pingxiao1 and LONG Guilu1,2 (key laboratory for quantum information and measurements and Department of Physics, Tsinghua University, Beijing 100084, China 2. key laboratory for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084, China) [a]Department of Physics Tsinghua University Key Laboratory for Quantum Information and Measurements Beijing China [b]Tsinghua University Key Laboratory for Atomic and Molecular NanoSciences Beijing China

A six-state quantum key distribution scheme with measuring-basis encryption technique, which is based on the six-state protocol and the MBE protocol, is proposed. In this modified six-state quantum key distribution protocol, Alice and Bob use a control key to synchronize the use of their measuring-basis so that they always use the same measuring-basis. This modified six-state quantum key distribution protocol retains the advantage of higher security and at the same time has a higher efficiency.

关键词： quantum key distribution measuring-basis encrypted six-state security.

Dynamical Suppression of Decoherence in Two-Qubit quantum Memory

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Communications in Theoretical Physics 2005年第3X期44卷 459-462页

作者： LIU Xiao-Shu Department of Physics Tsinghua University Beijing 100084 China key laboratory for quantum information and measurements Beijing 100084 China

In this paper, we have detailedly studied the dynamical suppression of the phase damping for the two-qubit quantum memory of Ising model by the quantum "bang-bang" technique. We find the sequence of periodic radiofrequency pulses repetitively to flip the state of the two-qubit system and quantitatively find that these pulses can be used to effectively suppress the phase damping decoherence of the quantum memory and freeze the system state into its initial state. The general sequence of periodic radio-frequency pulses to suppress the phase damping of multi-qubit of Ising model is also given.

关键词： decoherence suppression quantum memory bang-bang technique Ising model

A scheme to implement the Deutsch-Josza algorithm on a superconducting charge-qubit quantum computer

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Progress in Natural Science:Materials International 2006年第6期16卷 594-599页

作者： HUO Wenyi and LONG Guilu (key laboratory for quantum information and measurements, and Department of Physics, Tsinghua University, Beijing 100084, China key laboratory for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084, China) [a]key laboratory for quantum information and measurements and Department of Physics Tsinghua University Bejjing China [b]key laboratory for Atomic and Molecular NanoSciences Tsinghua University Bejing China

We have studied the implementation of the Deutsch-Josza quantum algorithm in a superconducting charge-qubit quantum computer. Different from previous studies, we have used the inductance coupled system of You et al. The detailed pulse sequences have been designed for the four possible functions in a 2-qubit system. The result is generalized to an arbitrary n-qubit system. This scheme will be useful for practical implementation of the algorithm.

关键词： superconducting quantum computer Deutsch-Josza algorithm.

Realization of quantum permutation algorithm in high dimensional Hilbert space

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Chinese Physics B 2017年第6期26卷 42-46页

作者：陈东旭刘瑞丰张沛王云龙李宏荣高宏李福利 key laboratory of quantum information and quantum Optoelectronic Devices School of ScienceXi'an Jiaotong University key laboratory of quantum information University of Science and Technology of China

quantum algorithms provide a more efficient way to solve computational tasks than classical algorithms. We experimentally realize quantum permutation algorithm using light＇s orbital angular momentum degree of freedom. By exploiting the spatial mode of photons, our scheme provides a more elegant way to understand the principle of quantum permutation algorithm and shows that the high dimension characteristic of light＇s orbital angular momentum may be useful in quantum algorithms. Our scheme can be extended to higher dimension by introducing more spatial modes and it paves the way to trace the source of quantum speedup.

关键词： quantum permutation algorithm orbital angular momentum Fourier transformation

Frequency Stability of Atomic Clocks Based on Coherent Population Trapping Resonance in ^85Rb

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Chinese Physics Letters 2007年第7期24卷 1883-1885页

作者：刘璐郭涛邓科刘新元陈徐宗汪中 laboratory for quantum information and measurements School of Electronics Engineering and Computer Science Peking University Beijing 100871

An atomic clock system based on coherent population trapping （CPT） resonance in 85Rb is reported, while most past works about the CPT clock are in ST Rb. A new modulation method （full-hyperfine-frequency-splitting modulation） is presented to reduce the effect of light shift to improve the frequency stability of the CPT clock in SSRb. The experimental results show that the short-term frequency stability of the CPT clock in SSRb is in the order of 10^-10/s and the long-term frequency stability can achieve 1.5 × 10^-11/80000s, which performs as well as 87 Rb in CPT resonance. This very good frequency stability performance associated with the low-cost and low-power properties of SSRb indicates that an atomic clock based on CPT in SSRb should be a promising candidate for making the chip scale atomic clock.

关键词： ATOMIC clocks RESONANCE COHERENT states FREQUENCY stability RUBIDIUM MODULATION (Electronics)

Adjusting the properties of the photon generated via an optical parametric oscillator by using a pulse pumped laser

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Chinese Physics B 2011年第11期20卷 267-273页

作者：陈嵩史保森郭光灿 key laboratory of quantum information University of Science and Technology of China

The cavity-enhanced spontaneous parametric down-conversion far below threshold can be used to generate a narrow-band photon pair efficiently. Previous experiments on the cavity-enhanced spontaneous parametric down- conversion almost always utilize continuous wave pump light, but the pulse pumped case is rarely reported. One disadvantage of the continuous wave case is that the photon pair is produced randomly within the coherence time of the pump, which limits its application in the quantum information realm. However, a pulse pump can help to solve this problem. In this paper, we theoretically analyze pulse pumped cavity-enhanced spontaneous parametric down- conversion in detail and show how the pump pulse affects the multi-photon interference visibility, two-photon waveform, joint spectrum and spectral brightness.

关键词： spontaneous parametric down-conversion photon pulse pumped quantum optics