通用的辅助量子计算

设计了一个通用的辅助量子计算协议。该协议的客户端Alice仅拥有经典计算机或有限的量子技术,这些资源不足以让Alice做通用量子计算,因此Alice需要把她的量子计算任务委派给远程的量子服务器Bob。Bob拥有充分成熟的量子计算机,并会诚实地帮助Alice执行委派的量子计算任务,但他却得不到Alice的任何输入、输出信息。该协议只要求Alice能发送量子态和执行Pauli门操作,协议具有通用性、半盲性、正确性和可验证性。     

辅助量子比特驱动型通用盲量子计算

应用量子隐形传态将Broadbent等人提出的通用盲量子计算(universal blind quantum computation)模型和辅助量子比特驱动型量子计算(ancilla-driven universal quantum computation)模型进行结合, 构造一个新的混合模型来进行计算。此外, 用计算寄存器对量子纠缠的操作来代替量子比特测量操作。因为后者仅限于两个量子比特, 所以代替后的计算优势十分明显。基于上述改进, 设计了实现辅助驱动型通用盲量子计算的协议。协议的实现, 能够使Anders等人的辅助驱动型量子计算增强计算能力, 并保证量子计算的正确性, 从而使得参与计算的任何一方都不能获得另一方的保密信息。     

Single-server blind quantum computation with quantum circuit model

Blind quantum computation (BQC) enables the client, who has few quantum technologies, to delegate her quantum computation to a server, who has strong quantum computabilities and learns nothing about the client’s quantum inputs, outputs and algorithms. In this article, we propose a single-server BQC protocol with quantum circuit model by replacing any quantum gate with the combination of rotation operators. The trap quantum circuits are introduced, together with the combination of rotation operators, such that the server is unknown about quantum algorithms. The client only needs to perform operations X and Z, while the server honestly performs rotation operators.     

Multi-server blind quantum computation over collective-noise channels

Blind quantum computation (BQC) enables ordinary clients to securely outsource their computation task to costly quantum servers. Besides two essential properties, namely correctness and blindness, practical BQC protocols also should make clients as classical as possible and tolerate faults from nonideal quantum channel. In this paper, using logical Bell states as quantum resource, we propose multi-server BQC protocols over collective-dephasing noise channel and collective-rotation noise channel, respectively. The proposed protocols permit completely or almost classical client, meet the correctness and blindness requirements of BQC protocol, and are typically practical BQC protocols.     

Finite-data-size study on practical universal blind quantum computation

The universal blind quantum computation with weak coherent pulses protocol is a practical scheme to allow a client to delegate a computation to a remote server while the computation hidden. However, in the practical protocol, a finite data size will influence the preparation efficiency in the remote blind qubit state preparation (RBSP). In this paper, a modified RBSP protocol with two decoy states is studied in the finite data size. The issue of its statistical fluctuations is analyzed thoroughly. The theoretical analysis and simulation results show that two-decoy-state case with statistical fluctuation is closer to the asymptotic case than the one-decoy-state case with statistical fluctuation. Particularly, the two-decoy-state protocol can achieve a longer communication distance than the one-decoy-state case in this statistical fluctuation situation.     

Multi-party blind quantum computation protocol with mutual authentication in network

Blind quantum computation (BQC) can ensure a client with limited quantum capability safely delegates computing tasks to a remote quantum server.In order to resi...     

Graph-theoretic quantum system modelling for information/computation processing circuits

This paper introduces graph-theoretic quantum system modelling (GTQSM), which is facilitated by considering the fundamental unit of quantum computation and information, viz. a quantum bit or qubit as a basic building block. Unit directional vectors ‘ket 0’ and ‘ket 1’ constitute two distinct fundamental quantum across variable orthonormal basis vectors (for the Hilbert space) specifying the direction of propagation, as it were, of information (or computation data) while complementary fundamental quantum through (flow rate) variables specify probability parameters (or amplitudes) as surrogates for scalar quantum information measure (von Neumann entropy). Applications of GTQSM are presented for quantum information/computation processing circuits ranging from a simple qubit and superposition or product of two qubits through controlled NOT and Hadamard gate operations to a substantive case of 3-port, 5-stage circuit for quantum teleportation. An illustrative circuit for teleporting a qubit is modelled as a complex ‘system of systems’ resulting in four probable transfer function models. It has the potential of extending the applications of GTQSM further to systems at the higher end of complexity scale too. The key contribution of this paper lies in generalization or extension of the graph-theoretic system modelling framework, hitherto used for classical (mostly deterministic) systems, to quantum random systems. Further extension of the graph-theoretic system modelling framework to quantum field modelling is the subject of future work.     

Universal access in e-voting for the blind

Since the inception of elections and election technologies, all segments of the voting population have never been granted equal access, privacy and security to voting. Modern electronic voting systems have made attempts to include disabled voters but have fallen short. Using recent developments in technology a secure, user centered, multimodal electronic voting system has been developed to study a multimodal approach for providing equity in access, privacy and security in electronic voting. This article will report findings from a study at the Alabama Institute for the Deaf and Blind where more than thirty-five blind or visually impaired participants used the multimodal voting system. The findings suggest that the proposed multimodal approach to voting is easy to use and trustworthy.     

Improving ancilla states for quantum computation

We analyze the improvement in output state fidelity upon improving the construction accuracy of ancilla states. Specifically, we simulate gates and syndrome measurements on a single qubit of information encoded into the [[7,1,3]] quantum error correction code and determine the output state fidelity as a function of the accuracy with which Shor states (for syndrome measurements) and magic states (to implement T-gates) are constructed. When no syndrome measurements are applied during the gate sequence, we observe that the fidelity increases after performance of a T-gate and improving magic states construction slows the fidelity decay rate. In contrast, when syndrome measurements are applied, loss of fidelity occurs primarily after the syndrome measurements taken after a T-gate. Improving magic state construction slows the fidelity decay rate, and improving Shor state construction raises the initial fidelity but does not slow the fidelity decay rate. Along the way, we show that applying syndrome measurements after every gate does not maximize the output state fidelity. Rather, syndrome measurements should be applied sparingly.     

Controlled gates for multi-level quantum computation

Multi-level (ML) quantum logic can potentially reduce the number of inputs/outputs or quantum cells in a quantum circuit which is a limitation in current quantum technology. In this paper we propose theorems about ML-quantum and reversible logic circuits. New efficient implementations for some basic controlled ML-quantum logic gates, such as three-qudit controlled NOT, Cycle, and Self Shift gates are proposed. We also propose lemmas about r-level quantum arrays and the number of required gates for an arbitrary n-qudit ML gate. An equivalent definition of quantum cost (QC) of binary quantum gates for ML-quantum gates is introduced and QC of controlled quantum gates is calculated.     

应用量子盲签名和群签名的电子支付系统

提出了一个基于量子群签名和盲签名电子支付系统的实现方案。基于经典的签名的现有的电子支付系统不能保证无条件安全性。与经典的电子支付系统不同,提出的方案既能满足电子支付系统的需求,又能实现无条件安全。应用量子密钥分发技术,量子一次一密算法和审计机制实现了基于量子签名的电子支付系统。     

A hybrid approach for stereo disparity computation

An alternative, hybrid approach for disparity estimation, based on the phase difference technique, is presented. The proposed technique combines the robustness of the matching method with the sub-pixel accuracy of the phase difference approach. A matching between the phases of the left and right signals is introduced in order to allow the phase difference method to work in a reduced disparity range. In this framework, a new criterion to detect signal singularities is proposed. The presented test cases show that the performance of the proposed technique in terms of accuracy and density of the disparity estimates has greatly improved. Received: 24 June 1997 / Accepted: 15 September 1998     

Methodology for modelling SPMD hybrid parallel computation

This research defines and analyzes a methodology for deriving a performance model for SPMD hybrid parallel applications. Hybrid parallelism combines shared memory and message passing computing models. This work extends the current practice of application performance modelling by development of a methodology for hybrid applications with these procedures.

• Creation of a model based on complexity analysis of an application code and its data structures.
• Enhancement of a static complexity model by dynamic factors to capture execution time phenomena, such as memory hierarchy effects.
• Quantitative analysis of model characteristics and the effects of perturbations in measured parameters.

These research results are presented in the context of a hybrid parallel implementation of a sparse linear algebra kernel. A model for this kernel is derived and analyzed using the methodology. Application of the model on two large parallel computing platforms provides case studies for the methodology. Operating system issues, machine balance factor, and memory hierarchy effects on model accuracy are examined. Copyright © 2007 John Wiley & Sons, Ltd.     

Toward quantum computation: a five-qubit quantum processor

Quantum physics presents intriguing possibilities for achieving computational gains after conventional miniaturization reaches its limits. Accordingly, we describe a nuclear magnetic-resonance quantum computer demonstrating a quantum algorithm that exponentially outperforms classical algorithms     

Qsimulation:一个量子计算模拟器工具

介绍一个可在经典计算机上模拟量子计算的工具Qsimulation。该工具由4个主要部分组成：一个命令式的量子编程语言,一个量子计算解释器,一个用于模拟量子程序执行的图形用户界面以及错误处理模块,它能帮助教师和新手设计并测试简单的量子电路和量子程序。     

Mathematical models of quantum computation

In this paper, we introduce two mathematical models of realistic quantum computation. First, we develop a theory of bulk quantum computation such as NMR (Nuclear Magnetic Resonance) quantum computation. For this purpose, we define bulk quantum Turing machine (BQTM for short) as a model of bulk quantum computation. Then, we define complexity classes EBQP, BBQP and ZBQP as counterparts of the quantum complexity classes EQP, BQP and ZQP, respectively, and show that EBQP=EQP, BBQP=BQP and ZBQP=ZQP. This implies that BQTMs are polynomially related to ordinary QTMs as long as they are used to solve decision problems. We also show that these two types of QTMs are also polynomially related when they solve a function problem which has a unique solution. Furthermore, we show that BQTMs can solve certain instances of NP-complete problems efficiently. On the other hand, in the theory of quantum computation, only feed-forward quantum circuits are investigated, because a quantum circuit represents a sequence of applications of time evolution operators. But, if a quantum computer is a physical device where the gates are interactions controlled by a current computer such as laser pulses on trapped ions, NMR and most implementation proposals, it is natural to describe quantum circuits as ones that have feedback loops if we want to visualize the total amount of the necessary hardware. For this purpose, we introduce a quantum recurrent circuit model, which is a quantum circuit with feedback loops. LetC be a quantum recurrent circuit which solves the satisfiability problem for a blackbox Boolean function includingn variables with probability at least 1/2. And lets be the size ofC (i.e. the number of the gates inC) andt be the number of iterations that is needed forC to solve the satisfiability problem. Then, we show that, for those quantum recurrent circuits, the minimum value ofmax(s, t) isO(n ²2 ^n/3). Tetsuro Nishino, D.Sc.: He is presently an Associate Professor in the Department of Information and Communication Engineering, The University of Electro-Communications. He received the B.S., M.S. and D.Sc degrees in mathematics from Waseda University, in 1982, 1984 and 1991 respectively. From 1984 to 1987, he joined Tokyo Research Laboratory, IBM Japan. From 1987 to 1992, he was a Research Associate of Tokyo Denki University, and from 1992 to 1994, he was an Associate Professor of Japan Advanced Institute of Science and Technology, Hokuriku. His main interests are circuit complexity theory, computational learning theory and quantum complexity theory.     

Tree search and quantum computation

Traditional tree search algorithms supply a blueprint for modeling problem solving behaviour. A diverse spectrum of problems can be formulated in terms of tree search. Quantum computation, namely Grover’s algorithm, has aroused a great deal of interest since it allows for a quadratic speedup to be obtained in search procedures. In this work we consider the impact of incorporating classical search concepts alongside Grover’s algorithm into a hybrid quantum search system. Some of the crucial points examined include: (1) the reverberations of contemplating the use of non-constant branching factors; (2) determining the consequences of incorporating an heuristic perspective into a quantum tree search model.     

A fast hybrid computation model for rectum deformation

It is a challenging task to realistically reproduce the complex deformation of soft bio-tissues in a surgical operation, especially when large deformations and movements exist. A hybrid model which we call the beads-on-string model is presented to handle the deformation and collision of the rectum in a virtual surgery simulation system. Specially tailored for this purpose, our model takes multiple layers to capture the dynamics of the rectum in an efficient manner. Inspired by the shape similarity between a rectum with regular bulges and a string of beads, we use a Cosserat rod model, coinciding with the centreline of the rectum, to calculate its deformation subject to external forces. We introduce rigid spheres, analogy to beads, moving along with the rod to approximate the shape of the rectum in handling collision. In addition, the beads (rigid spheres) provide a natural interlayer to map the deformation of the centreline to the associated mesh which presents detailed geometry of the rectum. Our approach is carefully crafted to achieve high computational efficiency and its multi-layer structure is designed to reproduce the physics of the deformation of the rectum.     

Scalable hybrid computation with spikes

We outline a hybrid analog-digital scheme for computing with three important features that enable it to scale to systems of large complexity: First, like digital computation, which uses several one-bit precise logical units to collectively compute a precise answer to a computation, the hybrid scheme uses several moderate-precision analog units to collectively compute a precise answer to a computation. Second, frequent discrete signal restoration of the analog information prevents analog noise and offset from degrading the computation. And, third, a state machine enables complex computations to be created using a sequence of elementary computations. A natural choice for implementing this hybrid scheme is one based on spikes because spike-count codes are digital, while spike-time codes are analog. We illustrate how spikes afford easy ways to implement all three components of scalable hybrid computation. First, as an important example of distributed analog computation, we show how spikes can create a distributed modular representation of an analog number by implementing digital carry interactions between spiking analog neurons. Second, we show how signal restoration may be performed by recursive spike-count quantization of spike-time codes. And, third, we use spikes from an analog dynamical system to trigger state transitions in a digital dynamical system, which reconfigures the analog dynamical system using a binary control vector; such feedback interactions between analog and digital dynamical systems create a hybrid state machine (HSM). The HSM extends and expands the concept of a digital finite-state-machine to the hybrid domain. We present experimental data from a two-neuron HSM on a chip that implements error-correcting analog-to-digital conversion with the concurrent use of spike-time and spike-count codes. We also present experimental data from silicon circuits that implement HSM-based pattern recognition using spike-time synchrony. We outline how HSMs may be used to perform learning, vector quantization, spike pattern recognition and generation, and how they may be reconfigured.