quantum Computation has shown a lot of promise in being able to provide computational results not possible with the modern computer. However, the design of new algorithms has been slow. One reason for this could be th...
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ISBN:
(纸本)9781424403622
quantum Computation has shown a lot of promise in being able to provide computational results not possible with the modern computer. However, the design of new algorithms has been slow. One reason for this could be that we simply do not understand this new paradigm of computation enough to fully utilize it. We present here is an improvement of our previous generalization the basic quantum gates and a new perspective on quantum computation and quantuminformation. The goal is to obtain a more abstract approach to quantum Computation and quantumalgorithms in which physical systems are viewed as the implementation for the computing paradigm and not the reason for the it.
We deal with the problem of finding a maximum of a function from the Holder class on a quantum computer We show matching lower and upper bounds oil the complexity of this problem. We prove upper bounds by constructing...
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We deal with the problem of finding a maximum of a function from the Holder class on a quantum computer We show matching lower and upper bounds oil the complexity of this problem. We prove upper bounds by constructing an alogorithm that uses a pre-exisiting quantum algorithm for finding maximum of a discrete sequence. To prove lower bounds we use results for finding the logical OR of sequence of bits. We show that quantum computation yields a quadratic speed-up over deterministic and randomized algorithms.
A possible way to optically simulate quantumalgorithms is by making use of the spatial distribution of light in a laser beam. In this approach, the quantum states are represented by the amplitudes of the electromagne...
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A possible way to optically simulate quantumalgorithms is by making use of the spatial distribution of light in a laser beam. In this approach, the quantum states are represented by the amplitudes of the electromagnetic field in the beam. Temporal evolution is simulated by using optical elements such as lenses and phase shifters. Different elements are required depending on the operation whose implementation is desired. In this paper, we present an optical module to simulate the Hadamard transformation operating on a single qubit. The system is composed by a set of lenses, a phase plate and a phase grating and it could be used as a part of more complex arrangements. As an example, we make use of our Hadamard optical module as a part of the quantum circuit that solves the Deutsch problem. We show the obtained experimental results and we discuss the limitations of the proposal. (c) 2006 Elsevier B.V. All rights reserved.
During the last ten years quantuminformationprocessing and Communication (QIPC) has established itself as one of the new hot topic fields in physics, with the potential to revolutionize many areas of science and tec...
ISBN:
(数字)9781614990185
ISBN:
(纸本)9781586036607
During the last ten years quantuminformationprocessing and Communication (QIPC) has established itself as one of the new hot topic fields in physics, with the potential to revolutionize many areas of science and technology. QIPC replaces the laws of classical physics applied to computation and communication with the more fundamental laws of quantum mechanics. This becomes increasingly important due to technological progress going down to smaller and smaller scales where quantum effects start to be dominant. In addition to its fundamental nature, QIPC promises to advance computing power beyond the capabilities of any classical computer, to guarantee secure communication and establish direct links to emerging quantum technologies, such as, for example, quantum based sensors and clocks. One of the outstanding feature of QIPC is its interdisciplinary character: it brings together researchers from physics, mathematics and computer science. In particular, within physics we have seen the emergence of a new QIPC community, which ranges from theoretical to experimental physics, and crosses boundaries of traditionally separated disciplines such as atomic physics, quantum optics, statistical mechanics and solid state physics, all working on different and complementary aspects of QIPC. This publication covers the following topics: Introduction to quantum computing; quantum logic, information and entanglement; quantumalgorithms; Error-correcting codes for quantum computations; quantum measurements and control; quantum communication; quantum optics and cold atoms for quantuminformation; quantum computing with solid state devices; Theory and experiments for superconducting qubits; Interactions in many-body systems: quantum chaos, disorder and random matrices; Decoherence effects for quantum computing; and Flature prospects of quantuminformationprocessing.
The last two decades feature an ever-increasing interest in quantuminformationprocessing - generalization of the classical computational models in the view of quantum Mechanics (QM). In theory, quantum computational...
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ISBN:
(纸本)0769526438
The last two decades feature an ever-increasing interest in quantuminformationprocessing - generalization of the classical computational models in the view of quantum Mechanics (QM). In theory, quantum computational devices are capable of solving in polynomial time problems for which only algorithms with exponential time complexity are known. Such enormous advantage explains the global scale of scientific efforts for creating the quantum Computer - physical realization of such computational device. While the results of those efforts are still constrained inside the large experimental laboratories, an adequate tool for studying quantumalgorithms will be of great help for educating the next generation of computer scientists - the engineers that will be responsible for operating these devices. The paper describes a quantum computer simulation model that exhibits a certain attractive property - the simulation slowdown does not depend directly on the size of the input data but rather on the complexity of the quantum state, meaning that transformations upon less-entangled data are performed faster Based on this property the simulation can be spread between the nodes of a GRID cluster in a way as to keep the entanglement in each job minimal.
On one hand, image segmentation is a low-level processing task which consists in partitioning an image into homogeneous regions. It can be seen as being a combinatorial optimization problem. In fact, considering the h...
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quantuminformationprocessing has attracted a lot of attention in recent years because of the promise it holds for faster, better, and more secure future communications. The most advanced field in quantuminformation...
quantuminformationprocessing has attracted a lot of attention in recent years because of the promise it holds for faster, better, and more secure future communications. The most advanced field in quantuminformationprocessing is quantum cryptography, also referred to as quantum key distribution (QKD), which uses the quantum properties of light to ensure the unconditionally secure transmission of a secret message between two parties. Despite the significant progress achieved in the performance of quantum cryptography systems, the communication distance has been limited to a few tens of kilometers and the communication speed remains very low, preventing the integration of these systems into current telecommunication networks. The main limiting factors are the vulnerability of existing QKD algorithms to powerful eavesdropping attacks, and the characteristics of the single-photon detectors employed in the system. This work addresses both of these limiting factors. We introduce and prove the security of a new quantum cryptography algorithm, the differential phase shift QKD protocol, which requires a very simple system architecture and only standard telecommunication components, such as lasers, detectors, and linear optics. The security proof against the most general attacks allowed by quantum mechanics reveals that this protocol is very robust to powerful eavesdropping attacks. Furthermore, we develop a new single-photon detector, which combines frequency up-conversion in a periodically poled lithium niobate waveguide and a silicon avalanche photodiode to achieve high speed and efficient single-photon detection in the telecommunication wavelength band. By combining these key elements of a quantum cryptography system, we demonstrate the experimental realization of practical and efficient fiber-optic QKD systems, with which we achieved communication at a rate of 2 Mbit/s over 10 km, and transmission of secure messages over 100 km of optical fiber. Compared to existing s
quantum computation can be understood as transformation of information encoded in the state of a quantum physical system. The basic idea behind quantum computation is to encode data using quantum bits (qubits). Differ...
quantum computation can be understood as transformation of information encoded in the state of a quantum physical system. The basic idea behind quantum computation is to encode data using quantum bits (qubits). Differently from the classical bit, the qubit can be in a superposition of basic states leading to "quantum parallelism", which is an important characteristic of quantum computation since it can greatly increase the speed processing of algorithms. However, quantum data types are computationally very powerful not only due to superposition. There are other odd properties like measurement and entangled. In this thesis we argue that a realistic model for quantum computations should be general with respect to measurements, and complete with respect to the information flow between the quantum and classical worlds. We thus explain and structure general and complete quantum programming in Haskell using well known constructions from classical semantics and programming languages, like monads and arrows. In more detail, this thesis focuses on the following contributions. Monads and Arrows. quantum parallelism, entanglement, and measurement certainly go beyond "pure" functional programming. We have shown that quantum parallelism can be modelled using a slightly generalisation of monads called indexed monads, or Kleisli structures. We have also build on this insight and showed that quantum measurement can be explained using a more radical generalisation of monads, the so-called arrows, more specifically, indexed arrows, which we define in this thesis. This result connects "generic" and "complete" quantum features to well-founded semantics constructions and programming languages. Understanding of Interpretations of quantumMechanics as Computational Effects. In a thought experiment, Einsten, Podolsky, and Rosen demonstrate some counter-intuitive consequences of quantum mechanics. The basic idea is that two entangled particles appear to always communicate some information ev
quantum computation promises solution to problems that are hard to solve by classical computers. The efficient construction of quantum circuits that can solve interesting tasks is a fundamental challenge in the field....
quantum computation promises solution to problems that are hard to solve by classical computers. The efficient construction of quantum circuits that can solve interesting tasks is a fundamental challenge in the field. Such efficient construction also reduces decoherence losses in physical implementations of quantumalgorithms by reducing interaction time with the environment. Therefore, finding time-optimal ways to synthesize unitary transformations from available physical resources is a problem of both fundamental and practical interest in quantuminformationprocessing. In this thesis, we study these problems in general mathematical frame as well as in some concrete real physical settings. We give a complete characterization of all the unitary transformations that can be synthesized in a given time for a two-qubit system in presence of general time varying coupling tensor, assuming that the local unitary transformation on two qubits can be performed arbitrarily fast (on a time scale governed by the strength of couplings). A generalization of this result on general Lie group is also presented. We then give the time optimal ways for coherence transfer on three linearly coupled spin chain, and an efficient way of constructing a CNOT gate between two indirectly coupled spins.
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