scholarly journals APPLICATIONS OF ATOMIC ENSEMBLES IN DISTRIBUTED QUANTUM COMPUTING

2010 ◽  
Vol 08 (01n02) ◽  
pp. 181-218 ◽  
Author(s):  
MARCIN ZWIERZ ◽  
PIETER KOK
Keyword(s):  
Quantum Information ◽  
Quantum Computation ◽  
Quantum Computer ◽  
Success Probability ◽  
Quantum Memory ◽  
Quantum Network ◽  
Atomic Ensembles ◽  
Cluster States ◽  
Ghz States ◽  
Single Qubit

Thesis chapter. The fragility of quantum information is a fundamental constraint faced by anyone trying to build a quantum computer. A truly useful and powerful quantum computer has to be a robust and scalable machine. In the case of many qubits which may interact with the environment and their neighbors, protection against decoherence becomes quite a challenging task. The scalability and decoherence issues are the main difficulties addressed by the distributed model of quantum computation. A distributed quantum computer consists of a large quantum network of distant nodes — stationary qubits which communicate via flying qubits. Quantum information can be transferred, stored, processed and retrieved in decoherence-free fashion by nodes of a quantum network realized by an atomic medium — an atomic quantum memory. Atomic quantum memories have been developed and demonstrated experimentally in recent years. With the help of linear optics and laser pulses, one is able to manipulate quantum information stored inside an atomic quantum memory by means of electromagnetically induced transparency and associated propagation phenomena. Any quantum computation or communication necessarily involves entanglement. Therefore, one must be able to entangle distant nodes of a distributed network. In this article, we focus on the probabilistic entanglement generation procedures such as well-known DLCZ protocol. We also demonstrate theoretically a scheme based on atomic ensembles and the dipole blockade mechanism for generation of inherently distributed quantum states so-called cluster states. In the protocol, atomic ensembles serve as single qubit systems. Hence, we review single-qubit operations on qubit defined as collective states of atomic ensemble. Our entangling protocol requires nearly identical single-photon sources, one ultra-cold ensemble per physical qubit, and regular photodetectors. The general entangling procedure is presented, as well as a procedure that generates in a single stepQ-qubit GHZ states with success probability psuccess ~ ηQ/2, where η is the combined detection and source efficiency. This is significantly more efficient than any known robust probabilistic entangling operation. The GHZ states form the basic building block for universal cluster states, a resource for the one-way quantum computer.

scholarly journals Quantum Switchboard with Coupled-Cavity Array

2021 ◽  
Author(s):  
Wai-Keong Mok ◽  
Leong-Chuan Kwek
Keyword(s):  
Quantum Information ◽  
Quantum Computation ◽  
Scaling Up ◽  
Quantum Network ◽  
Quantum Cloning ◽  
Physical Implementation ◽  
Large Quantum ◽  
Coupled Cavity ◽  
Cavity Array

The ability to control the flow of quantum information deterministically is useful for scaling up quantum computation. In this paper, we demonstrate a controllable quantum switchboard which directs the teleportation protocol to one of two targets, fully dependent on the sender’s choice. The quantum switchboard additionally acts as a optimal quantum cloning machine. We also provide a physical implementation of the proposal using a coupled-cavity array. The proposed switchboard can be utilized for the efficient routing of quantum information in a large quantum network.

scholarly journals DECOHERENCE-FREE QUANTUM MEMORY FOR PHOTONIC STATE USING ATOMIC ENSEMBLES

2009 ◽  
Vol 07 (04) ◽  
pp. 811-820 ◽  
Author(s):  
FENG MEI ◽  
YA-FEI YU ◽  
ZHI-MING ZHANG
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Large Scale ◽  
Quantum Information Processing ◽  
Single Photon ◽  
Quantum Memory ◽  
Single Photon Detection ◽  
Atomic Ensembles ◽  
Optical Elements ◽  
Photonic State

Large scale quantum information processing requires stable and long-lived quantum memories. Here, using atom-photon entanglement, we propose an experimentally feasible scheme to realize decoherence-free quantum memory with atomic ensembles, and show one of its applications, remote transfer of unknown quantum state, based on laser manipulation of atomic ensembles, photonic state operation through optical elements, and single-photon detection with moderate efficiency. The scheme, with inherent fault-tolerance to the practical noise and imperfections, allows one to retrieve the information in the memory for further quantum information processing within the reach of current technology.

CLUSTER STATE QUANTUM COMPUTATION AND THE REPEAT-UNTIL-SUCCESS SCHEME

2008 ◽  
Vol 22 (01n02) ◽  
pp. 33-43 ◽  
Author(s):  
L. C. KWEK
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Cluster State ◽  
Entangled State ◽  
Single Qubit ◽  
Computation Process ◽  
Measurement Results ◽  
Basic Ideas ◽  
The One ◽  
Computational Basis

Cluster state computation or the one way quantum computation (1WQC) relies on an initially highly entangled state (called a cluster state) and an appropriate sequence of single qubit measurements along different directions, together with feed-forward based on the measurement results, to realize a quantum computation process. The final result of the computation is obtained by measuring the last remaining qubits in the computational basis. In this short tutorial on cluster state quantum computation, we will also describe the basic ideas of a cluster state and proceed to describe how a single qubit operation can be done on a cluster state. Recently, we proposed a repeat-until-success (RUS) scheme that could effectively be used to realize one-way quantum computer on a hybrid system of photons and atoms. We will briefly describe this RUS scheme and show how it can be used to entangled two distant stationary qubits.

scholarly journals COMPUTER QUANTISTICI: STATUS E PROSPETTIVE

2020 ◽  
Author(s):  
Lorenzo Maccone
Keyword(s):  
Quantum Information ◽  
Quantum Computation ◽  
Quantum Computer

A quantum computer is a system that is able to process quantum information. In this presentation I’ll briefly explain what is it and what are the main results of the current research in the field of quantum computation.

scholarly journals Modelling of Grover’s quantum search algorithms: implementations of Simple quantum simulators on classical computers

2020 ◽  
pp. 65-128
Author(s):  
Sergey Ulyanov ◽  
Andrey Reshetnikov ◽  
Olga Tyatyushkina
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Search Algorithm ◽  
Quantum Circuit ◽  
Unitary Matrix ◽  
Single Qubit ◽  
Simple Quantum ◽  
Grover’S Search Algorithm ◽  
The Cost ◽  
Universal Gate

Models of Grover’s search algorithm is reviewed to build the foundation for the other algorithms. Thereafter, some preliminary modifications of the original algorithms by others are stated, that increases the applicability of the search procedure. A general quantum computation on an isolated system can be represented by a unitary matrix. In order to execute such a computation on a quantum computer, it is common to decompose the unitary into a quantum circuit, i.e., a sequence of quantum gates that can be physically implemented on a given architecture. There are different universal gate sets for quantum computation. Here we choose the universal gate set consisting of CNOT and single-qubit gates. We measure the cost of a circuit by the number of CNOT gates as they are usually more difficult to implement than single qubit gates and since the number of single-qubit gates is bounded by about twice the number of CNOT’s.

scholarly journals Measurement-Based Quantum Computation

2021 ◽  
Author(s):  
Tzu-Chieh Wei
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Cluster State ◽  
Quantum Circuit ◽  
Cluster States ◽  
Local Measurements ◽  
Potential Alternative ◽  
The One ◽  
Alternative Resource ◽  
Classical Spin Models

Measurement-based quantum computation is a framework of quantum computation, where entanglement is used as a resource and local measurements on qubits are used to drive the computation. It originates from the one-way quantum computer of Raussendorf and Briegel, who introduced the so-called cluster state as the underlying entangled resource state and showed that any quantum circuit could be executed by performing only local measurement on individual qubits. The randomness in the measurement outcomes can be dealt with by adapting future measurement axes so that computation is deterministic. Subsequent works have expanded the discussions of the measurement-based quantum computation to various subjects, including the quantification of entanglement for such a measurement-based scheme, the search for other resource states beyond cluster states and computational phases of matter. In addition, the measurement-based framework also provides useful connections to the emergence of time ordering, computational complexity and classical spin models, blind quantum computation, and so on, and has given an alternative, resource-efficient approach to implement the original linear-optic quantum computation of Knill, Laflamme, and Milburn. Cluster states and a few other resource states have been created experimentally in various physical systems, and the measurement-based approach offers a potential alternative to the standard circuit approach to realize a practical quantum computer.

scholarly journals Quantum Mechanics and the Origin of Life

2004 ◽  
Vol 213 ◽  
pp. 237-244
Author(s):  
Paul Davies
Keyword(s):  
Quantum Mechanics ◽  
Information Processing ◽  
Quantum Information ◽  
Quantum Computation ◽  
Origin Of Life ◽  
Quantum Information Processing ◽  
Quantum Computer ◽  
The Origin Of Life ◽  
Concept Of Information

The race to build a quantum computer has led to a radical re-evaluation of the concept of information. In this paper I conjecture that life, defined as an information processing and replicating system, may be exploiting the considerable efficiency advantages offered by quantum computation, and that quantum information processing may dramatically shorten the odds for life originating from a random chemical soup. The plausibility of this conjecture rests, however, on life somehow circumventing the decoherence effects of the environment. I offer some speculations on ways in which this might happen.

scholarly journals Universal quantum computation with shutter logic

2006 ◽  
Vol 6 (6) ◽  
pp. 495-515
Author(s):  
J.C. Garcia-Escartin ◽  
P. Chamorro-Posada
Keyword(s):  
Quantum Computation ◽  
Quantum Logic ◽  
Quantum Computer ◽  
Quantum Memory ◽  
Linear Optics ◽  
Cnot Gate ◽  
Free Model ◽  
Universal Quantum

We show that universal quantum logic can be achieved using only linear optics and a quantum shutter device. With these elements, we design a quantum memory for any number of qubits and a CNOT gate which are the basis of a universal quantum computer. An interaction-free model for a quantum shutter is given.

scholarly journals Systematic distillation of composite Fibonacci anyons using one mobile quasiparticle

2012 ◽  
Vol 12 (9&10) ◽  
pp. 876-892
Author(s):  
Ben W. Reichardt
Keyword(s):  
Quantum Computation ◽  
Quantum Computer ◽  
Fault Tolerant ◽  
Success Probability ◽  
Quantum Algorithm ◽  
Systematic Construction ◽  
Topological Quantum ◽  
Universal Quantum ◽  
Measurement Devices ◽  
Topological Quantum Computation

A topological quantum computer should allow intrinsically fault-tolerant quantum computation, but there remains uncertainty about how such a computer can be implemented. It is known that topological quantum computation can be implemented with limited quasiparticle braiding capabilities, in fact using only a single mobile quasiparticle, if the system can be properly initialized by measurements. It is also known that measurements alone suffice without any braiding, provided that the measurement devices can be dynamically created and modified. We study a model in which both measurement and braiding capabilities are limited. Given the ability to pull nontrivial Fibonacci anyon pairs from the vacuum with a certain success probability, we show how to simulate universal quantum computation by braiding one quasiparticle and with only one measurement, to read out the result. The difficulty lies in initializing the system. We give a systematic construction of a family of braid sequences that initialize to arbitrary accuracy nontrivial composite anyons. Instead of using the Solovay-Kitaev theorem, the sequences are based on a quantum algorithm for convergent search.

scholarly journals CONSTRUCTING 2D AND 3D CLUSTER STATES WITH PHOTONIC MODULES

2010 ◽  
Vol 08 (01n02) ◽  
pp. 149-159 ◽  
Author(s):  
RADU IONICIOIU ◽  
WILLIAM J. MUNRO
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Computation ◽  
Large Scale ◽  
Quantum Information Processing ◽  
Quantum Repeater ◽  
Cluster States ◽  
Optical Processor ◽  
Quantum Optical ◽  
2D And 3D

Large-scale quantum information processing and distributed quantum computation require the ability to perform entangling operations on a large number of qubits. We describe a new photonic module which prepares, deterministically, photonic cluster states using an atom in a cavity as an ancilla. Based on this module, we design a network for constructing 2D cluster states and then we extend the architecture to 3D topological cluster states. Advantages of our design include a passive switching mechanism and the possibility of using global control pulses for the atoms in the cavity. The architecture described here is well-suited for integrated photonic circuits on a chip and could be used as a basis of a future quantum optical processor or in a quantum repeater node.

Sign in / Sign up

Export Citation Format

Share Document