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The quantum theory of indirect measurements in physical systems is studied. The example of an indirect measurement of an observable represented by a self-adjoint operator $\mathcal{N}$ with finite spectrum is analysed in detail. The…

Mathematical Physics · Physics 2017-09-12 M. Ballesteros , N. Crawford , M. Fraas , J. Fröhlich , B. Schubnel

Projective measurement is used as a fundamental axiom in quantum mechanics, even though it is discontinuous and cannot predict which measured operator eigenstate will be observed in which experimental run. The probabilistic Born rule gives…

Quantum Physics · Physics 2017-08-09 Apoorva Patel , Parveen Kumar

Experimental determination of an unknown quantum state usually requires several incompatible measurements. However, it is also possible to determine the full quantum state from a single, repeated measurement. For this purpose, the quantum…

Quantum Physics · Physics 2008-03-25 Xinhua Peng , Jiangfeng Du , Dieter Suter

We consider highly inaccurate measurements made on classical stochastic and quantum systems. In the quantum case such a \e{weak} measurement preserves coherence between the system's alternatives. We demonstrate that in both cases the…

Quantum Physics · Physics 2026-03-16 D. Sokolovski , D. Alonso , S. Brouard

We suggest and describe how to analyze new types of experiments that would test a proposed model of the quantum measurement process. That model produces the Born Rule as a corollary, and so agrees with conventional quantum predictions. The…

Quantum Physics · Physics 2025-08-22 Alan Schaum

The possibility of determining the state of a quantum system after a continuous measurement of position is discussed in the framework of quantum trajectory theory. Initial lack of knowledge of the system and external noises are accounted…

Quantum Physics · Physics 2009-10-31 A. C. Doherty , S. M. Tan , A. S. Parkins , D. F. Walls

A collapse-free version of quantum theory is examined to systematically study the role of the projection postulate. This foil theory assumes "passive" measurements that do not update quantum states although measurement outcomes still occur…

Quantum Physics · Physics 2025-08-27 Vincenzo Fiorentino , Stefan Weigert

There are several theories or processes which may underlie quantum mechanics and make it deterministic. Some references are given in the main text. Any such theory, plus a number of reasonable assumptions, implies the existence of what I…

Quantum Physics · Physics 2023-04-10 L. S. Schulman

In this paper, we extend the standard formalism of quantum mechanics to a quantum theory for a total system including one internal measuring apparatus. The internality of the measuring apparatus implies that different decomposition of a…

Quantum Physics · Physics 2012-05-17 Wen-ge Wang

Quantum mechanics is an extremely successful theory that agrees with every experiment. However, the principle of linear superposition, a central tenet of the theory, apparently contradicts a commonplace observation: macroscopic objects are…

Quantum Physics · Physics 2015-03-20 Angelo Bassi , Kinjalk Lochan , Seema Satin , Tejinder P. Singh , Hendrik Ulbricht

The presence of noise in quantum computers hinders their effective operation. Even though quantum error correction can theoretically remedy this problem, its practical realization is still a challenge. Testing and benchmarking noisy,…

Quantum Physics · Physics 2023-02-15 Adrian Ortega , Orsolya Kálmán , Tamás Kiss

Throughout quantum mechanics there is statistical balance, in the collective response of an ensemble of systems to differing measurement types. Statistical balance is a core feature of quantum mechanics, underlying quantum mechanical…

Quantum Physics · Physics 2022-10-31 Brian Drummond

Measurements with randomly chosen settings determine many important properties of quantum states without the need for a shared reference frame or calibration. They naturally emerge in the context of quantum communication and quantum…

Observations or measurements taken of a quantum system (a small number of fundamental particles) are inherently random. If the state of the system depends on unknown parameters, then the distribution of the outcome depends on these…

Statistics Theory · Mathematics 2007-06-13 Richard D. Gill

Randomized measurement protocols, including classical shadows, entanglement tomography, and randomized benchmarking are powerful techniques to estimate observables, perform state tomography, or extract the entanglement properties of quantum…

Quantum Physics · Physics 2024-04-03 Jacob Bringewatt , Jonathan Kunjummen , Niklas Mueller

Self-testing refers to the possibility of characterizing an unknown quantum device based only on the observed statistics. Here we develop methods for self-testing entangled quantum measurements, a key element for quantum networks. Our…

Quantum Physics · Physics 2022-05-24 Marc-Olivier Renou , Jędrzej Kaniewski , Nicolas Brunner

In this paper we are interested to model quantum signal by statistical signal processing methods. The Gaussian distribution has been considered for the input quantum signal as Gaussian state have been proven to a type of important robust…

Quantum Physics · Physics 2023-02-17 Mouli Chakraborty , Harun Siljak , Indrakshi Dey , Nicola Marchetti

Self-testing is a method of quantum state and measurement estimation that does not rely on assumptions about the inner working of the used devices. Its experimental realization has been limited to sources producing single quantum states so…

We study the problem of quantum-state tomography under the assumption that the state of the system is close to pure. In this context, an efficient measurements that one typically formulates uniquely identify a pure state from within the set…

Quantum Physics · Physics 2016-05-11 Amir Kalev , Charles H. Baldwin , Ivan H. Deutsch

Increasingly sophisticated programmable quantum simulators and quantum computers are opening unprecedented opportunities for exploring and exploiting the properties of highly entangled complex quantum systems. The complexity of large…