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Recently, it has been stated that single-world interpretations of quantum theory are logically inconsistent. The claim is derived from contradicting statements of agents in a setup combining two Wigner's-friend experiments. Those statements…

Quantum Physics · Physics 2016-11-04 Veronika Baumann , Arne Hansen , Stefan Wolf

In textbooks, ideal quantum measurements are described in terms of the tested system only by the collapse postulate and Born's rule. This level of description offers a rather flexible position for the interpretation of quantum mechanics.…

Quantum Physics · Physics 2017-09-28 Theo M. Nieuwenhuizen , Marti Perarnau-Llobet , Roger Balian

Ultimately, any explanation of quantum measurement must be extendable to relativistic quantum mechanics (RQM), since many precisely confirmed experimental results follow from quantum field theory (QFT), which is based on RQM. Certainly, the…

Quantum Physics · Physics 2025-04-08 Ed Seidewitz

We consider the problem of determining the state of a quantum system given one or more readings of the expectation value of an observable. The system is assumed to be a finite dimensional quantum control system for which we can influence…

Quantum Physics · Physics 2009-11-10 Domenico D'Alessandro

Post-inflationary boundary conditions are essential to the existence of our highly structured universe, and these can only come about through quantum mechanical state reductions - i.e., through measurements. The choice is between: An…

Quantum Physics · Physics 2007-05-23 Richard A Mould

In the measurement of a continuous observable Q, the pure components of the reduced state do, in general, depend on the initial state. For measurements which attempt to localize the measured system in a certain region R, the localized wave…

High Energy Physics - Phenomenology · Physics 2007-05-23 Kai J. Druhl

In this paper, we present a collection of results on the observability of quantum mechanical systems, in the case the output is the result of a discrete nonselective measurement. By defining an effective observable we extend previous…

Quantum Physics · Physics 2007-05-23 D. D'Alessandro , R. Romano

We describe in a qualitative way a possible picture of the Measurement Process in Quantum Mechanics, which takes into account: 1. the finite and non zero time duration T of the interaction between the observed system and the microscopic…

Quantum Physics · Physics 2018-02-20 Sergio Doplicher

We present a generic model of (non-destructive) quantum measurement. Being formulated within reversible quantum mechanics, the model illustrates a mechanism of a measurement process --- a transition of the measured system to an eigenstate…

Quantum Physics · Physics 2017-11-06 Karl-Erik Eriksson , Martin Cederwall , Kristian Lindgren , Erik Sjöqvist

The Semiotic Interpretation (SI) of QM pushes further the Von Neumann point of view that `experience only makes statements of this type: an observer has made a certain observation; and never any like this: a physical quantity has a certain…

Quantum Physics · Physics 2007-05-23 Jean Schneider

We show that the key problems of quantum measurement theory, namely the reduction of the wave packet of a microsystem and the specification of its quantum state by a macroscopic measuring instrument, may be rigorously resolved within the…

Mathematical Physics · Physics 2009-11-11 Geoffrey Sewell

In the general theory of quantum measurement, one associates a positive semidefinite operator on a $d$-dimensional Hilbert space to each of the $n$ possible outcomes of an arbitrary measurement. In the special case of a projective…

Quantum Physics · Physics 2021-11-23 Yizhou Liu , John B. DeBrota

The standard approach to quantum measurements is to assume that they lead to effectively instantaneous collapse of the quantum state. However, if we assume that we are unable to enforce at what exact moment of time the measurement occurs…

Quantum Physics · Physics 2026-03-20 Igor Prlina , Milutin Živković

During a continuous measurement, quantum systems can be described by a stochastic Schr\"odinger equation which, in the appropriate limit, reproduces the von Neumann wave-function collapse. The average behavior on the ensemble of all…

Condensed Matter · Physics 2009-10-30 Carlo Presilla , Ubaldo Tanbini

The measurement problem remains unaddressed in modern physics, with an array of proposed solutions but as of yet no agreed resolution. In this paper, we examine measurement using the Q-based, objective-field model for quantum mechanics.…

Quantum Physics · Physics 2026-01-07 Channa Hatharasinghe , Ashleigh Willis , Run Yan Teh , P. D. Drummond , M. D. Reid

The measurement problem in quantum mechanics arises from the apparent collapse of a superposition state to a definite outcome when a measurement is made. Although treating the measuring apparatus as a classical system has been a successful…

Quantum Physics · Physics 2023-08-09 Vishwas KS

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 mechanism by which an effective macroscopic description of quantum measurement in terms of discrete, probabilistic collapse events emerges from the reversible microscopic dynamics remains an enduring open question. Emerging quantum…

The measurement processes that are traditionally described within the realm of non-relativistic quantum mechanics are transcribed into the covariant framework of Cartan's space, the four-valued representation space of the restricted…

Quantum Physics · Physics 2026-01-19 J. G. Cardoso

Measurement of an observable on a quantum system involves a probabilistic collapse of the quantum state and a corresponding measurement outcome. L\"uders and von Neumann state update rules attempt to describe the above phenomenological…

Quantum Physics · Physics 2019-08-19 C. S. Sudheer Kumar , Abhishek Shukla , T. S. Mahesh