Quantum Private Query Based on Stable Error Correcting Code in the Case of Noise

In order to protect the privacy of query users and databases, a quantum private query protocol under noisy conditions is proposed and studied. It is a one-way quantum protocol that not only protects user privacy, but also prevents eavesdropping. And in the protocol initialization phase, the identity is verified by the quantum entanglement pair. Through key distribution, a user only knows a part of the key, and the accuracy of the original key needs to be considered. Channel noise directly affects the transmission result of quantum bits and reduces the transmission accuracy. In addition, the presence of eavesdropper Eve may also affect the transmission of qubits. The receiver corrects the error by using quantum error correction technology, thereby improving the efficiency of protocol communication.

     

Application of Quantum Gauss-Jordan Elimination Code to Quantum Secret Sharing Code

International Journal of Theoretical Physics - The QSS codes associated with a MSP code are based on finding an invertible matrix V, solving the system $mathbf {v}_{A}^{T}M_{B} left (begin...     

Quantum Cosmological Perfect Fluid Models

Perfect fluid Friedmann-Robertson-Walker quantum cosmological models for an arbitrary barotropic equation of state p = are constructed using Schutz's variational formalism. In this approach the notion of time can be recovered. By superposition of stationary states, finite-norm wave-packet solutions to the Wheeler-DeWitt equation are found. The behaviour of the scale factor is studied by applying the many-worlds and the ontological interpretations of quantum mechanics. Singularity-free models are obtained for < 1. Accelerated expansion at present requires –1/3 > > – 1.     

Quantum Key Distribution Using High-Dimensional Quantum Error-Avoiding Code

Using high-dimensional quantum error-avoiding code, we present two new quantum key distribution protocols over a collective noisy channel, i.e. six-photon and five-photon quantum error-avoiding codes. Compared with the previous protocols using four-photon and three-photon quantum error-avoiding code, the qubit efficiencies of the new protocols have increases of 16.67% and 5% respectively. In addition, the security of these protocols is analysed with a conclusion that the new protocols are much more secure than the four-photon and three-photon ones.     

基于六光子量子避错码的量子密钥分发方案

量子信道中不可避免存在的噪声将扭曲被传输的信息,对通信造成危害。目前克服量子信道噪声的较好方案是量子避错码（QEAC）。将量子避错码思想用于量子密钥分发,能有效克服信道中的噪声,且无需复杂的系统。用六光子构造了量子避错码,提出了一种丛于六光子避错码的量子密钥分发（QDK）方案。以提高量子密钥分发的量子比特效率和安全性为前提,对六光子避错码的所有可能态进行组合,得到一种六光子避错码的最优组合方法,可将两比特信息编码在一个态中,根据测肇结果和分组信息进行解码,得到正确信息的平均概率为7／16。与最近的基于四光子避错码的克服量子信道噪声的量子密钥分发方案相比,该方案的量子比特效率提高了16．67％,密钥分发安全性足它的3．5倍。     

Error Symmetrization in Quantum Computers

Errors in quantum computers are of two kinds:sudden perturbations to isolated qubits, and slow,random drifts of all the qubits. Isolated errors can becorrected by using quantum codewords that represent a logical qubit in a redundant way, by severalphysical qubits. On the other hand, slow drifts can bereduced, but not completely eliminated, by means ofsymmetrization, namely by using many replicas of the computer, and forcing their joint quantumstate to be completely symmetric. Several symmetrizationstrategies are examined and analyzed.     

A Novel Deterministic Quantum Communication Scheme Using Stabilizer Quantum Code

Exploiting the encoding process of the stabilizer quantum code [[n, k, d]], a deterministic quantum communication scheme, in which n - 1 photons are distributed forward and backward in two-way channel, is proposed to transmit the secret messages with unconditional security. The present scheme can be implemented to distribute the secret quantum （or classical） messages with great capacity in imperfect quantum channel since the utilized code encodes k-qubit messages for each scheme run.     

The Quantum Commutator Algebra of a Perfect Fluid

A perfect fluid is quantized by the canonical method. The constraints are found and this allows the Dirac brackets to be calculated. Replacing the Dirac brackets with quantum commutators formally quantizes the system. There is a momentum operator in the denominator of some coordinate quantum commutators. It is shown that it is possible to multiply throughout by this momentum operator. Factor ordering differences can result in a viscosity term. The resulting quantum commutator algebra is unusual.     

一种抗光扰动的矢量纠偏方法研究

在半球成像系统实时跟踪目标的过程中,从受到光扰动影响的圆环像中迅速准确地提取圆环的中心是一个关键,为了适应半球成像系统跟踪目标的实时性和抗扰性能要求,根据圆的几何对称性,提出了一种矢量纠偏的抗光扰动的圆环中心确定方法,实验结果表明,对于无扰动的圆环图像其误差小于1个像素;对于有扰动的图环像误差不超过5个像素。     

Quantum Secret Sharing with Error Correction

We investigate in this work a quantum error correction on a five-qubits graph state used for secret sharing through five noisy channels. We describe the procedure for the five, seven and nine qubits codes. It is known that the three codes always allow error recovery if only one among the sent qubits is disturbed in the transmitting channel. However, if two qubits and more are disturbed, then the correction will depend on the used code. We compare in this paper the three codes by computing the average fidelity between the sent secret and that measured by the receivers. We will treat the case where, at most, two qubits are affected in each one of five depolarizing channels.     

Quantum Secret Sharing with Error Correction

We investigate in this work a quantum error correction on a five-qubits graph state used for secret sharing through five noisy channels. We describe the procedure for the five, seven and nine qubits codes. It is known that the three codes always allow error recovery if only one among the sent qubits is disturbed in the transmitting channel. However, if two qubits and more are disturbed, then the correction will depend on the used code. We compare in this paper the three codes by computing the average fidelity between the sent secret and that measured by the receivers. We will treat the case where, at most, two qubits are affected in each one of five depolarizing channels.     

自然科学研究中的"纠错机制"及其推广——科学与人文漫话之十二

论述了自然科学研究中“纠错机制”的理论基础、实施步骤及其推广到人文社会科学研究中的有关问题．     

Asymptotic Error Rates in Quantum Hypothesis Testing

We consider the problem of discriminating between two different states of a finite quantum system in the setting of large numbers of copies, and find a closed form expression for the asymptotic exponential rate at which the error probability tends to zero. This leads to the identification of the quantum generalisation of the classical Chernoff distance, which is the corresponding quantity in classical symmetric hypothesis testing. The proof relies on two new techniques introduced by the authors, which are also well suited to tackle the corresponding problem in asymmetric hypothesis testing, yielding the quantum generalisation of the classical Hoeffding bound. This has been done by Hayashi and Nagaoka for the special case where the states have full support. The goal of this paper is to present the proofs of these results in a unified way and in full generality, allowing hypothesis states with different supports. From the quantum Hoeffding bound, we then easily derive quantum Stein’s Lemma and quantum Sanov’s theorem. We give an in-depth treatment of the properties of the quantum Chernoff distance, and argue that it is a natural distance measure on the set of density operators, with a clear operational meaning.     

Nested Quantum Error Correction Codes via Subgraphs

Because of its directness and simplicity, using graph is a worthy researching approach to construct quantum error correction codes. Nested graphical quantum code is a special class of stabilizer codes. In this letter, by making uses of the entanglement of several subgraphs, we proposed a novel construction method of generator matrices of graphical quantum nested codes, and families of corresponding nested graphical quantum codes.     

Multi-Bits Transfer Based on the Quantum Three-Stage Protocol with Quantum Error Correction Codes

International Journal of Theoretical Physics - This paper presents a multi-bits transfer quantum protocol based on the three-stage quantum cryptography in which both parties use their own secret...     

Unitary Application of the Quantum Error Correction Codes

For applying the perfect code to transmit quantum information over a noise channel, the standard protocol contains four steps: the encoding, the noise channel, the error-correction operation, and the decoding. In present work, we show that this protocol can be simplified. The error-correction operation is not necessary if the decoding is realized by the so-called complete unitary transformation. We also offer a quantum circuit, which can correct the arbitrary single-qubit errors.