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Environment-induced decoherence presents a great challenge to realizing a quantum computer. We point out the somewhat surprising fact that decoherence can be useful, indeed necessary, for practical quantum computation, in particular, for…

Quantum Physics · Physics 2007-07-24 R. Srikanth , Subhashish Banerjee

The dynamics of open quantum system are often modeled by non-Markovian processes that account for memory effects arising from interactions with the environment. It is well-known that the memory provided by the environment can be classical…

Quantum Physics · Physics 2025-10-22 Charlotte Bäcker , Konstantin Beyer , Walter T. Strunz

We can learn (more) about the state a quantum system is in through measurements. We look at how to describe the uncertainty about a quantum system's state conditional on executing such measurements. We show that by exploiting the interplay…

Quantum Physics · Physics 2025-04-22 Keano De Vos , Gert de Cooman

A molecular MCB junction in the partially wet phase has been used to probe effects related to open quantum systems. Although the exact quantum system, environment, and coupling, are not known the nature of the experiments shows a…

Mesoscale and Nanoscale Physics · Physics 2024-12-09 C. J. Muller

We study quantum Darwinism--the redundant recording of information about the preferred states of a decohering system by its environment--for an object illuminated by a black body. In the cases of point-source and isotropic illumination, we…

Quantum Physics · Physics 2010-07-13 C. Jess Riedel , Wojciech H. Zurek

In reinforcement learning, an agent interacts sequentially with an environment to maximize a reward, receiving only partial, probabilistic feedback. This creates a fundamental exploration-exploitation trade-off: the agent must explore to…

Quantum Physics · Physics 2026-03-27 Josep Lumbreras , Ruo Cheng Huang , Yanglin Hu , Marco Fanizza , Mile Gu

The place and role of an Observer in quantum mechanics has been a subject of an ongoing debate since the theory's inception. Wigner brought this question to the fore in a celebrated scenario in which a super-Observer observes a Friend…

Quantum Physics · Physics 2020-09-14 A. Matzkin , D. Sokolovski

Why do we need quantization to describe vision? What are the quadrature operators of the electromagnetic field? Is it possible to measure them? What are the characteristic functions useful for? In this brief tutorial we provide the…

Quantum Physics · Physics 2021-10-08 Stefano Olivares

Using a master-equation approach for the description of coherent and incoherent dynamics in `artificial atoms and molecules', we present a theoretical analysis of situations where intense laser fields lead to pronounced renormalizations of…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Ulrich Hohenester , Filippo Troiani , Elisa Molinari

Quantum Darwinism attempts to explain the emergence of objective reality of the state of a quantum system in terms of redundant information about the system acquired by independent non interacting fragments of the environment. The…

Quantum Physics · Physics 2019-07-10 Nadia Milazzo , Salvatore Lorenzo , Mauro Paternostro , G. Massimo Palma

We derived quantum trajectories for a system interacting with the environment prepared in a continuous mode single photon state as the limit of discrete filtering model with an environment defined as series of independent qubits prepared…

Quantum Physics · Physics 2020-02-11 Anita Dabrowska , Gniewomir Sarbicki , Dariusz Chruscinski

An open quantum system in steady state $\hat\rho_{ss}$ can be represented by a weighted ensemble of pure states $\hat\rho_{ss}=\sum_{k}\wp_{k}\ket{\psi_k} \bra{\psi_k}$ in infinitely many ways. A physically realizable (PR) ensemble is one…

Quantum Physics · Physics 2009-11-07 H. M. Wiseman , John A. Vaccaro

It is shown that if the wave function of a quantum system undergoes an arbitrary random transformation such that the diagonal elements of the density matrix in the decoherence basis associated with a preferred observable remain constant,…

Quantum Physics · Physics 2025-04-24 Dorje C. Brody , Lane P. Hughston

Wigner's friend experiment and its modern extensions display the ambiguity of the quantum mechanical description regarding the assignment of quantum states. While the friend applies the state-update rule to the system upon observing an…

Quantum Physics · Physics 2025-10-22 Flavio Del Santo , Gonzalo Manzano , Caslav Brukner

The purpose of quantum tomography is to determine an unknown quantum state from measurement outcome statistics. There are two obvious ways to generalize this setting. First, our task need not be the determination of any possible input state…

Quantum Physics · Physics 2014-02-11 Claudio Carmeli , Teiko Heinosaari , Jussi Schultz , Alessandro Toigo

The positive operator (valued) measures (POMs) allow one to generalize the notion of observable beyond the traditional one based on projection valued measures (PVMs). Here, we argue that this generalized conception of observable enables a…

Quantum Physics · Physics 2011-01-04 Paul Busch , Gregg Jaeger

The state that an observer attributes to a quantum system depends on the information available to that observer. If two or more observers have different information about a single system, they will in general assign different states. Is…

Quantum Physics · Physics 2007-05-23 Todd A. Brun

Environment induced decoherence, and other quantum processes, have been proposed in the literature to explain the apparent spontaneous selection - out of the many mathematically eligible bases - of a privileged measurement basis that…

General Physics · Physics 2016-09-27 Hitoshi Inamori

In the modern quantum mechanics of cosmology observers are physical systems within the universe. They have no preferred role in the formulation of the theory nor in its predictions of third person probabilities of what occurs. However,…

General Relativity and Quantum Cosmology · Physics 2018-01-18 James Hartle , Thomas Hertog

The objective, classical world emerges from the underlying quantum substrate via the proliferation of redundant copies of selected information into the environment, which acts as a communication channel, transmitting that information to…

Quantum Physics · Physics 2017-03-30 Michael Zwolak , Wojciech H. Zurek