78,822 research outputs found
Evading quantum mechanics
Quantum mechanics is potentially advantageous for certain
information-processing tasks, but its probabilistic nature and requirement of
measurement back action often limit the precision of conventional classical
information-processing devices, such as sensors and atomic clocks. Here we show
that by engineering the dynamics of coupled quantum systems, it is possible to
construct a subsystem that evades the measurement back action of quantum
mechanics, at all times of interest, and obeys any classical dynamics, linear
or nonlinear, that we choose. We call such a system a quantum-mechanics-free
subsystem (QMFS). All of the observables of a QMFS are quantum-nondemolition
(QND) observables; moreover, they are dynamical QND observables, thus
demolishing the widely held belief that QND observables are constants of
motion. QMFSs point to a new strategy for designing classical
information-processing devices in regimes where quantum noise is detrimental,
unifying previous approaches that employ QND observables, back-action evasion,
and quantum noise cancellation. Potential applications include
gravitational-wave detection, optomechanical force sensing, atomic
magnetometry, and classical computing. Demonstrations of dynamical QMFSs
include the generation of broad-band squeezed light for use in interferometric
gravitational-wave detection, experiments using entangled atomic spin
ensembles, and implementations of the quantum Toffoli gate.Comment: v2: changed the title, added a figure, and made some minor update
Inseparability of Quantum Parameters
In this work, we show that 'splitting of quantum information' [6] is an
impossible task from three different but consistent principles of unitarity of
Quantum Mechanics, no-signalling condition and non increase of entanglement
under Local Operation and Classical Communication.Comment: 9 pages, Presented in Quantum Computing Back Action in IIT Kanpur
(2006). Accepted in International Journal of Theoretical Physic
Universal low-temperature properties of quantum and classical ferromagnetic chains
We identify the critical theory controlling the universal, low temperature,
macroscopic properties of both quantum and classical ferromagnetic chains. The
theory is the quantum mechanics of a single rotor. The mapping leads to an
efficient method for computing scaling functions to high accuracy.Comment: 4 pages, 2 tables and 3 Postscript figure
Quantum nonlinear dynamics of continuously measured systems
Classical dynamics is formulated as a Hamiltonian flow on phase space, while
quantum mechanics is formulated as a unitary dynamics in Hilbert space. These
different formulations have made it difficult to directly compare quantum and
classical nonlinear dynamics. Previous solutions have focussed on computing
quantities associated with a statistical ensemble such as variance or entropy.
However a more direct comparison would compare classical predictions to the
quantum for continuous simultaneous measurement of position and momentum of a
single system. In this paper we give a theory of such measurement and show that
chaotic behaviour in classical systems can be reproduced by continuously
measured quantum systems.Comment: 11 pages, REVTEX, 3 figure
Introduction to Quantum Computing for Graduate Students in Chemistry
Treball Final de Grau en Química. Codi: QU0943. Curs acadèmic: 2020/2021Aims
1- To provide an overview of the concepts of classical computation and quantum
mechanics on which quantum computing is based.
2- Introduce the basic ideas about quantum computing and expose its main
differences with classical computing.
3- To program different examples of quantum computation with 3-qubit systems, as
well as Grover's search algorithm
Power and Energy Applications Based on Quantum Computing:The Possible Potentials of Grover’s Algorithm
In quantum computing, calculations are achieved using quantum mechanics. Typically, two main phenomena of quantum mechanics (i.e., superposition and entanglement) allow quantum computing to solve some problems more efficiently than classical algorithms. The most well-known advantage of quantum computing is the speedup of some of the calculations, which have been performed before by classical applications. Scientists and engineers are attempting to use quantum computing in different fields of science, e.g., drug discovery, chemistry, computer science, etc. However, there are few attempts to use quantum computing in power and energy applications. This paper tries to highlight this gap by discussing one of the most famous quantum computing algorithms (i.e., Grover’s algorithm) and discussing the potential applications of this algorithm in power and energy systems, which can serve as one of the starting points for using Grover’s algorithm in power and energy systems
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