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The states needed in a quantum computation are extremely affected by decoherence. Several methods have been proposed to control error spreading. They use two main tools: fault-tolerant constructions and concatenated quantum error correcting…

Quantum Physics · Physics 2007-05-23 Pedro J. Salas , Angel L. Sanz

We develop dynamical non-Markovian description of quantum computing in weak coupling limit, in lowest order approximation. We show that long range memory of quantum reservoir produces strong interrelation between structure of noise and…

Quantum Physics · Physics 2009-11-07 Robert Alicki , Michal Horodecki , Pawel Horodecki , Ryszard Horodecki

We study a decoherence reduction scheme that involves an intermediate measurement on the qubit in an equal superposition basis, in the general framework of all qubit-environment interactions that lead to qubit pure decoherence. We show…

Quantum Physics · Physics 2024-02-22 Bartosz Rzepkowski , Katarzyna Roszak

The dynamics of a decohering two-level system driven by a suitable control Hamiltonian is studied. The control procedure is implemented as a sequence of radiofrequency pulses that repetitively flip the state of the system, a technique that…

Quantum Physics · Physics 2009-10-31 Lorenza Viola , Seth Lloyd

We study quantum decoherence numerically in a system consisting of a relativistic quantum field theory coupled to a measuring device that is itself coupled to an environment. The measuring device and environment are treated as quantum,…

Quantum Physics · Physics 2020-10-13 Chris Nagele , Oliver Janssen , Matthew Kleban

It is difficult to evaluate the precision of quantum measurements because it is not possible to conduct a second reference measurement on the same physical system to compare the measurement outcome with a more accurate value of the measured…

Quantum Physics · Physics 2021-02-10 Holger F. Hofmann

Quantum parameter estimation has many applications, from gravitational wave detection to quantum key distribution. We present the first experimental demonstration of the time-symmetric technique of quantum smoothing. We consider both…

The quantum decoherence program has become more attractive in providing an acceptable solution for the long-standing quantum measurement problem. Decoherence by quantum entanglement happens very quickly to entangle the quantum system with…

Popular Physics · Physics 2023-01-04 Mani L. Bhaumik

Strong quantum-correlated sources are essential but delicate resources for quantum information science and engineering protocols. Decoherence and loss are the two main disruptive processes that lead to the loss of nonclassical behavior in…

We investigate the parameter estimation problem in a two-qubit system, in which each qubit is independently interacting with its Markovian environment. We study in detail the sensitivity of the estimation on the decoherence rate $\gamma$…

Quantum Physics · Physics 2014-01-14 Zheng Qiang , Yao Yao , Yong Li

Quantum systems can be used to measure various quantities in their environment with high precision. Often, however, their sensitivity is limited by the decohering effects of this same environment. Dynamical decoupling schemes are widely…

Quantum Physics · Physics 2018-07-18 David Layden , Paola Cappellaro

We utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical parameters…

It is commonly stated that decoherence in open quantum systems is due to growing entanglement with an environment. In practice, however, surprisingly often decoherence may equally well be described by random unitary dynamics without…

Quantum Physics · Physics 2009-10-29 Julius Helm , Walter T. Strunz

Aspects of coherence and decoherence are analyzed within the optical Bloch equations. By rewriting the analytic solution in an alternate form, we are able to emphasize a number of unusual features: (a) despite the Markovian nature of the…

Quantum Physics · Physics 2007-05-23 A. S. Sanz , H. Han , P. Brumer

Decoherence, resulting from unwanted interaction between a qubit and its environment, poses a serious challenge towards the development of quantum technologies. Recently, researchers have started analysing how real-time Hamiltonian learning…

Quantum Physics · Physics 2020-06-24 Eleanor Scerri , Erik M. Gauger , Cristian Bonato

Quantum metrology offers an enhanced performance in experiments such as gravitational wave-detection, magnetometry or atomic clocks frequency calibration. The enhancement, however, requires a delicate tuning of relevant quantum features…

Quantum Physics · Physics 2013-07-25 Jan Kolodynski , Rafal Demkowicz-Dobrzanski

Characterizing noisy quantum processes is important to quantum computation and communication (QCC), since quantum systems are generally open. To date, all methods of characterization of quantum dynamics (CQD), typically implemented by…

Quantum Physics · Physics 2015-01-28 S. Omkar , R. Srikanth , S. Banerjee

Quantum computers can be considered as a natural means for performing machine learning tasks for inherently quantum labeled data. Many quantum machine learning techniques have been developed for solving classification problems, such as…

Quantum Physics · Physics 2025-01-24 Andrey Kardashin , Yerassyl Balkybek , Vladimir V. Palyulin , Konstantin Antipin

The simulation of complex quantum systems on a quantum computer is studied, taking the kicked Harper model as an example. This well-studied system has a rich variety of dynamical behavior depending on parameters, displays interesting…

Quantum Physics · Physics 2007-05-23 Benjamin Levi , Bertrand Georgeot

In quantum information processing quantum operations are often processed alongside measurements which result in classical data. Due to the information gain of classical measurement outputs non-unitary dynamical processes can take place on…