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Accurate control of quantum systems requires precise measurement of the parameters that govern the dynamics, including control fields and interactions with the environment. Parameters will drift in time and experiments interleave protocols…

Quantum Physics · Physics 2020-02-11 Swarnadeep Majumder , Leonardo Andreta de Castro , Kenneth R. Brown

Any realist interpretation of quantum theory must grapple with the measurement problem and the status of state-vector collapse. In a no-collapse approach, measurement is typically modeled as a dynamical process involving decoherence. We…

Quantum Physics · Physics 2020-09-22 Jacob A. Barandes , David Kagan

The measurability by means of continuous measurements, of an observable $\A(t_0)$, at an instant, and of a time averaged observable, $\bar \A=1/T\int \A(t')dt'$, is examined for linear and in particular for non-linear quantum mechanical…

Quantum Physics · Physics 2007-05-23 Y. Aharonov , B. Reznik

Quantum metrology explores quantum effects to improve the measurement accuracy of some physical quantities beyond the classical limit. However, due to the interaction between the system and the environment, the decoherence can significantly…

Quantum Physics · Physics 2024-05-07 Cheng-Ge Liu , Cong-Wei Lu , Na-Na Zhang , Qing Ai

We provide an affirmative answer to the question posed in the title. Our argument is based on a treatment of the Schroedinger dynamics of the composite of a quantum microsystem, S, and a macroscopic measuring apparatus, I, consisting of N…

Quantum Physics · Physics 2009-11-13 Geoffrey Sewell

Quantum measurement is a physical process. A system and an apparatus interact for a certain time period (measurement time), and during this interaction, information about an observable is transferred from the system to the apparatus. In…

Quantum Physics · Physics 2016-10-31 Takayuki Miyadera

The effects of the measurement apparatus on quantum coherence are studied by considering a purely dephasing model of a qubit. The initial state is prepared from a thermal state of the whole system by performing a nonselective measurement on…

Quantum Physics · Physics 2021-12-22 Filippo Giraldi

The topic of measurement in relativistic quantum field theory is addressed in this article. Some of the long standing problems of this subject are highlighted, including the incompatibility of an instantaneous ``collapse of the…

Mathematical Physics · Physics 2024-11-21 Christopher J. Fewster , Rainer Verch

We consider the problem of a state determination for a two-level quantum system which can be in one of two nonorthogonal mixed states. It is proved that for the two independent identical systems the optimal combined measurement (which…

Quantum Physics · Physics 2007-05-23 A. E. Allahverdyan , D. B. Saakian

We address how one can empirically infer properties of quantum states generated by dynamics involving measurements. Our focus is on many-body settings where the number of measurements is extensive, making brute-force approaches based on…

Quantum Physics · Physics 2024-07-19 Max McGinley

Considering a general microscopic model for a quantum measuring apparatus comprising a quantum probe coupled to a thermal bath, we analyze the energetic resources necessary for the realization of a quantum measurement, which includes the…

Quantum Physics · Physics 2025-01-29 Camille L Latune , Cyril Elouard

We argue that measurement data in quantum physics can be rigorously interpreted only as a result of a statistical, macroscopic process, taking into account the indistinguishable character of identical particles. Quantum determinism is in…

General Physics · Physics 2025-07-22 Patrick Navez , Henni Ouerdane

We consider all pure or mixed states of a quantum many-body system which exhibit the same, arbitrary but fixed measurement outcome statistics for several commuting observables. Taking those states as initial conditions, which are then…

Statistical Mechanics · Physics 2019-04-08 B. N. Balz , J. Richter , J. Gemmer , R. Steinigeweg , P. Reimann

We consider the problem of characterizing the set of input-output correlations that can be generated by an arbitrarily given quantum measurement. Our main result is to provide a closed-form, full characterization of such a set for any qubit…

Quantum Physics · Physics 2017-06-26 Michele Dall'Arno , Sarah Brandsen , Francesco Buscemi , Vlatko Vedral

We propose a class of incompatibility measures for quantum observables based on quantifying the effect of a measurement of one observable on the statistics of the outcomes of another. Specifically, for a pair of observables $A$ and $B$ with…

Quantum Physics · Physics 2014-09-30 Prabha Mandayam , M. D. Srinivas

Measurement models (MMs) stand at the highest structural level of quantum measurement theory. MMs can be employed to construct instruments which stand at the next level. An instrument is thought of as an apparatus that is used to measure…

Quantum Physics · Physics 2023-08-22 Stan Gudder

The problem of measurement in quantum mechanics is reanalyzed within a general, strictly probabilistic framework (without reduction postulate). Based on a novel comprehensive definition of measurement the natural emergence of objective…

Quantum Physics · Physics 2007-05-23 Markus Simonius

The kind of information provided by a measurement is determined in terms of the correlation established between observables of the apparatus and the measured system. Using the framework of quantum measurement theory, necessary and…

Quantum Physics · Physics 2009-10-30 Paul Busch , Pekka Lahti

The standard quantum formalism introduced at the undergraduate level treats measurement as an instantaneous collapse. In reality however, no physical process can occur over a truly infinitesimal time interval. A more subtle investigation of…

Quantum Physics · Physics 2020-04-22 Leigh S. Martin

In an ideal quantum measurement, the wave function of a quantum system collapses to an eigenstate of the measured observable, and the corresponding eigenvalue determines the measurement outcome. If the observable commutes with the system…

Quantum Physics · Physics 2020-02-13 Dayou Yang , Andrey Grankin , Lukas M. Sieberer , Denis V. Vasilyev , Peter Zoller