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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.

Eavesdropping in a quantum secret sharing protocol based on Grover algorithm and its solution

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Science china(physics,Mechanics & Astronomy) 2010年第3期53卷 491-495页

作者： HAO liang1, li Junlin1 & long guilu1,2 1Key Laboratory for Atomic and Molecular NanoSciences and department of physics, tsinghua university, beijing 100084, china 2tsinghua National Laboratory for Information Science and Technology, beijing 100084, china 1. Key Laboratory for Atomic and Molecular NanoSciences and department of physics Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

A detailed analysis has showed that the quantum secret sharing protocol based on the Grover algorithm (Phys Rev A, 2003, 68: 022306) is insecure. A dishonest receiver may obtain the full information without being detected. A quantum secret-sharing protocol is presents here, which mends the security loophole of the original secret-sharing protocol, and doubles the information capacity.

关键词： quantum secret sharing Grover algorithm quantum cryptography quantum search algorithm

Arbitrarily long distance quantum communication using inspection and power insertion

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Chinese Science Bulletin 2009年第1期54卷 158-162页

作者： WANG WanYing1,2,WANG Chuan1,2,ZHANG GuangYu1,3 & long guilu1,2 1 department of physics,tsinghua university,beijing 100084,china 2 tsinghua National Laboratory for Information Science and Technology,tsinghua university,beijing 100084,china 3 College of Applied Science,Harbin university of Science and Technology,Harbin 150080,china department of physics Tsinghua University Beijing 100084 China tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China College of Applied Science Harbin University of Science and Technology Beijing 100084 China

The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this paper,a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial function of the dis-tance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret messages are transmitted directly over a quantum channel.

关键词：长距离量子通信量子安全通信量子密匙分布噪声

Calculation of light emission in sonoluminescence

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Science china(physics,Mechanics & Astronomy) 2009年第4期52卷 593-601页

作者： li ChaoHui1 & AN Yu1,2 1 department of physics,tsinghua university,beijing 100084,china 2 Institute of Acoustics,Chinese Academy of Sciences,beijing 100190,china department of physics Tsinghua University Beijing 100084 China Institute of Acoustics Chinese Academy of Sciences Beijing 100190 China

We modify a uniform model of single bubble sonoluminescence,in which heat diffusion,water vapor diffusion and chemical reactions are included to describe the bubble dynamics,and the processes of electron-atom bremsstrahlung,electron-ion bremsstrahlung and recombination radiation,radiative attachment of electrons to atoms and molecules,line emissions of OH radicals and Na atoms are taken into account to calculate the light emission. With this model,we compute the light pulse width,the photon number per flash,the continuum and line spectra and the gas species as the products of chemical reactions,and try to compare with all the experimental data available. We obtain good agreement with the observations of Ar and Xe bubbles in many cases,but fail to match the experimental data of the photon number per flash. We also find that for He bubble the computed photon number is always too small to interpret the observations.

关键词： sonoluminescence bremsstrahlung radiative attachment line spectrum collision broadening

Self-healing routing: failure,modeling and analysis

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Science china(Information Sciences) 2011年第3期54卷 609-622页

作者： XU MingWei 1,2 , li Qi 1,2 , YANG Yuan 1,2 , HOU MeiJia 1,2 & PAN lingTao 1,2 1 department of Computer Science, tsinghua university, beijing 100084, china 2 tsinghua National Laboratory for Information Science and Technology (TNlist), beijing 100084, china 1. department of Computer Science Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology (TNList) Beijing 100084 China

Network failures occur frequently, and self-healing ability of existing routing protocols cannot guarantee fast route convergence under these failures without impacting packet forwarding. During routing convergence, network routes may be incorrect and even routing black holes and loops occur, which will result in extensive packet loss and thus influence network performance. To solve this problem, several improved routing solutions have been proposed. In this paper, we propose the concept and model of self-healing routing and analyze the key problems in current intra-domain and inter-domain self-healing routing protocols after briefly reviewing the characteristics of network failures. We classify the different self-healing solutions into two categories based on their design principles: routing restoration and routing protection, and systematically analyze these different typical solutions. Finally, we discuss several key issues in self-healing routing and propose a hybrid protection and restoration based routing scheme.

关键词： failure intra-domain routing inter-domain routing self-healing routing

Experimental realization of quantum cryptography communication in free space

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Science china(physics,Mechanics & Astronomy) 2005年第2期48卷 237-246页

作者： WANG Chuan1, ZHANG Jingfu1, WANG Pingxiao1, DENG Fuguo1, AI Qing1 & long guilu1,2 1. department of physics, Key Laboratory for Quantum Information and Measurements, tsinghua Univer- sity, beijing 100084, china 2. Center for Atomic and Molecular NanoSciences, tsinghua university, beijing 100084, china department of physics Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing 100084 China Atomic and Molecular NanoSciences Tsinghua University Beijing 100084 China

Utilizing linear optical devices, the principle of B92 quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2 meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.

关键词： quantum key distribution, free space, linear optics, faint pulses.

Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

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Progress in Natural Science:Materials International 2007年第10期17卷 1147-1151页

作者： liu Dan1,2 , Zhang Yong3 and long guilu1,2(1. Key Laboratory for Atomic and Molecular NanoSciences, and department of physics, tsinghua university, beijing 100084, china 2. Center of Quantum Information Science and Technology, tsinghua National Laboratory for information Science and Technology, beijing 100084, china 3. Institute of physics, School of Sciences, beijing university of Posts and Telecommunications, beijing 100876, china) Key Laboratory for Atomic and Molecular NanoSciences and Department of Physics Tsinghua University Beijing 100084 China Center of Quantum Information Science and Technology Tsinghua National Laboratory for information Science and Technology Beijing 100084 China Institute of physics School of Sciences Beijing University of Posts and Telecommunications Beijing 100876 China

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ>3, namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.

关键词： Heisenberg-XY chain magnetic-current phase transition.

Two mode photon bunching effect as witness of quantum criticality in circuit QED

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Science china(physics,Mechanics & Astronomy) 2009年第12期52卷 1898-1905页

作者： AI Qing1,WANG YingDan2,long guilu1,3 & SUN ChangPu4 1 department of physics,tsinghua university,beijing 100084,china 2 department of physics,university of Basel,Klingelbergstrasse 82,4056 Basel,Switzerland 3 tsinghua National Laboratory for Information Science and Technology,beijing 100084,china 4 Institute of Theoretical physics,Chinese Academy of Sciences,beijing 100080,china 1. department of physics Tsinghua University Beijing 100084 China 2. department of physics University of Basel Klingelbergstrasse 82 4056 Basel Switzerland 3. tsinghua National Laboratory for Information Science and Technology Beijing 100084 China 4. Institute of Theoretical physics Chinese Academy of Sciences Beijing 100080 China

We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.

关键词： quantum phase transition photon bunching circuit QED

Entropy product measure for multipartite pure states

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Science china(physics,Mechanics & Astronomy) 2006年第5期49卷 606-615页

作者： CAO Wancang1,2, liU Dan2, PAN Feng3 & long guilu2,4 1. department of physics, Chifeng College, Chifeng 024001, china 2. Key Laboratory for Quantum Information and Measurements, department of physics, tsinghua university, beijing 100084, china 3. department of physics, liaoning Normal university, Dalian 116029, china 4. Key Laboratory for Atomic and Molecular Nano-Sciences, tsinghua university, beijing 100084, china Correspondence should be addressed to long guilu department of physics Chifeng College Chifeng 024001 China Key Laboratory for Quantum Information Measurements Department of Physics Tsinghua University Beijing 100084 China department of physics Liaoning Normal University Dalian 116029 China Key Laboratory for Atomic Molecular Nano-Sciences Tsinghua University Beijing 100084 China

An entanglement measure for multipartite pure states is formulated using the product of the von Neumann entropy of the reduced density matrices of the constituents. Based on this new measure, all possible ways of the maximal entanglement of the triqubit pure states are studied in detail and all types of the maximal entanglement have been compared with the result of ‘the average entropy’. The new measure can be used to calculate the degree of entanglement, and an improvement is given in the area near the zero entropy.

关键词： multipartite pure state von Neumann entropy entanglement measure