Decoherence, einselection, and the quantum origins of the. In this work, we observe the dynamical features of the quantum memory assisted entropic uncertainty relations eur for a pair of incompatible measurements in an open system characterized. Decoherence, then, results in the collapse of the quantum wave function and the settling of a particle into its observed state under classical physics, its transition from quantum to classical behavior. Pdf a decoherencefree quantum memory using trapped ions. A quantum state of an electron spin in the dot can be faithfully transfered into nuclear. Such decoherence and the necessity of using the relativistic schrodinger equation are discussed. We measured the storage time under ambient conditions and under interaction with an engineered noisy environment and. In our experiment, the coherence time of the quantum memory is limited by the decoherence due to loss of atoms, which can. The present invention is a method for reducing the rate of decoherence in quantum memory. Jul 21, 2014 quantum technologies rely on the ability to coherently transfer information encoded in quantum states along quantum channels.
Decoherence and the foundations of quantum mechanics. Elsevier physics letters a 243 1998 265269 6 july 1998 physics letters a scheme for reducing collective decoherence in quantum memory luming duan, guancan guo 1 department of physics and nonlinear science center, university of science and technology of china, hefei 230026, china received 24 march 1997. Operationinduced decoherence by nonrelativistic scattering from a quantum memory 11569 where jx,tj 1,2are scalar functions. Encoding the stored information into a decoherencefree. Decoherence and the transition from quantum to classical. Given the discussions of the previous two sections, we are finally ready to muse on the subject of decoherence in quantum gravity, emergence of time and the cosmological arrow of time, focusing on the case of dimensions. A decoherencefree quantum memory using trapped ions science.
Time evolution, according to schrodinger equation minicollapse when a result is observed by me. Maximilian schlosshauer in the 1980s, theoretical estimates showed that on macroscopic scales idecoherence occurs extremely rapidly, thus e. Over the course of the past decade, decoherence has become a ubiquitous scienti. As a result of the decoherence process in quantum computation, there is a need for techniques for restoring qubits that have decohered to their original superposition of states. Decoherencefree quantum memory using trapped ions nist. Pdf quantum coherent dynamics in single molecule systems. The importance of quantum decoherence in brain processes.
Robust quantum network memory using decoherence protected subspaces of nuclear spins andreas reiserer, norbert kalb, machiel s. Decoherence and the classical limit of quantum mechanics. Electronic spins in different environments are currently investigated as potential qubits, i. Environmental decoherence stabilizes quantum dot cellular automata enrique p. The spin bath is described by the lipkinmeshkovglick model and the bath spins are subjected to a transverse magnetic field. Decoherence effect on quantummemoryassisted entropic. However, interaction of a quantum memory with its environment destroys the stored information, a process called decoherence 4, 5. Part of the reason is that decoherence is not, in a certain sense, a truly fundamental mechanism amending quantum theory, but an applied mechanism introduced to explain collapse using ideas from statistical mechanics those density matrices and concepts of bathenvironment supplementing those of quantum mechanics. A decoherencefree quantum memory using trapped ions. Pdf we propose the generalized stochastic liouville equation to investigate the coherent dynamics in single molecule systems coupled to environments. Encoding the stored information into a decoherence free subspace, or dfs, allows the memory to. Scheme for reducing collective decoherence in quantum memory.
Quantum memory is a key element in information processing, such as optical quantum computing and quantum communication, while opening a new way for the foundation of lightatom interaction. Uncertainty principle significantly provides a bound to predict precision of measurement with regard to any two incompatible observables, and thereby plays a nontrivial role in quantum precision measurement. In the earliest discussions of quantum computing 1 the spatial variables are retained, although not in the form of the schrodinger equation. It also discusses the exacerbation of the problem through the inclusion of environmental interactions, the idea. Decoherence induced by the environment sets limits on the efficiency. In practice, it is crucial to include quantum memory decoherence for quantum repeaters that rely on twowa y communication ov er long distances as shown in 6. A quantum memory for this application needs to be highly efficient and have coherence times approaching a millisecond. Quantum memories are an integral component of quantum repeatersdevices that will allow the extension of quantum key distribution to communication ranges beyond that permissible by passive transmission. Indeed, i am surprised and gratified by how much the field has evolved over the last decade.
Pdf we analyze decoherence of a quantum register in the absence of nonlocal operations, i. Reducing decoherence in quantum computer memory with all quantum bits coupling to the same environment luming duan and guangcan guo department of physics and nonlinear science center, university of science and technology of china, hefei, anhui 230026, peoples republic of china abstract decoherence in quantum computer memory due to the. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system. Superposition, interference and decoherence quantum theory. With regard to classical information transmission down a memory channel, it was pointed out that it can be enhanced by using entangled input states 68, and coding theorems have been recently proved for classes of memory quantum channels 9, 10. Nonmarkovianity and reservoir memory of quantum channels. Recently an ensemble of nuclear spins in a quantum dot have been proposed as a longlived quantum memory. A millisecond quantum memory for scalable quantum networks. Basics of decoherence the key idea promoted by decoherence is rather simple, although its consequences are farreaching and seem to have been overlooked for a surprisingly long time. Lenta department of electrical engineering, university of notre dame, notre dame, indiana 46556, usa. The importance of quantum decoherence in brain processes max tegmark institute for advanced study, olden lane, princeton, nj 08540. Pdf decoherence of an nqubit quantum memory carlos.
A longlived memory qubit on a low decoherence quantum bus. Decoherence, the measurement problem, and interpretations of quantum mechanics bas hensen downing college cambridge cb2 1dq, uk june 24, 2010. To give a correct quantum mechanical account of the behavior and properties of a physical system, we must include. Decoherence has been hailed as the solution to longstanding foundational problems dating back to. Aug 04, 2003 on the basis of these models, certain types of decoherence are unavoidable. This immediately led to the question of how we may ex. Specifically, section 2 analyses the claim that decoherence solves the measurement problem. These have to retain memory of their quantum state for a sufficiently long time phase memory time, tm allowing quantum operations to be performed.
Decoherence, control, and symmetry in quantum computers. Synthetic approach to determine the effect of nuclear spin. Pdf a longlived memory qubit on a lowdecoherence quantum. Us5768297a method for reducing decoherence in quantum. Robust quantumnetwork memory using decoherenceprotected. Abstract we demonstrate a decoherence free quantum memory of one qubit. Quantum decoherence is the loss of quantum coherence. We study the quantum dynamics of a single qubit coupled to a bath of interacting spins as a model for decoherence in solid state quantum memories. A quantum state of an electron spin in the dot can be. Environmental decoherence stabilizes quantumdot cellular. Recently, an ensemble of nuclear spins in a quantum dot have been proposed as a longlived quantum memory. Reducing decoherence in quantum computer memory with all.
Focus on quantum memory new journal of physics iopscience. Decoherence of an nqubit quantum memory thomas gorin,1 carlos pineda,2,3,4, and thomas h. Decoherence, control, and symmetry in quantum computers by dave morris bacon double b. This entry mainly deals with the role of decoherence in relation to the main problems and approaches in the foundations of quantum mechanics. Protecting the dynamics of coupled quantum systems from decoherence by the environment is a key challenge for solidstate quantum information processing 1,2. We demonstrate a decoherence free quantum memory of one qubit. E july 2 1999, accepted october 25 based on a calculation of neural decoherence rates, we ar. Decoherence offers a theoretical framework in which the measurement problem can be swept under the carpet pushed into a system larger than that which we can observe. Decoherence, the measurement problem, and interpretations of.
Pdf quantum memory decoherencemitigating architecture. Decoherenceprotected quantum gates for a hybrid solidstate. Imho decoherence is the simplest, most intuitive qm model most consistent with other laws of physics. The role of decoherence was recognized by a wide spectrum of practicing. A central problem in quantum computing is decoherence, in which the pure state degrades to a mixed state, with deleterious effects for the computation.
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