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An Operational Approach to Quantum State Reduction

Masanao Ozawa

Published Jan 1, 1997• 30 citations
OpenAlex

Abstract

An operational approach to quantum state reduction, the state change of the measured system caused by a measurement of an observable conditional upon the outcome of measurement, is founded without assuming the projection postulate in any stages of the measuring process. Whereas the conventional formula assumes that the probe measurement satisfies the projection postulate, a new formula for determining the state reduction shows that the state reduction does not depend on how the probe observable is measured, or in particular does not depend on whether the probe measurement satisfies the projection postulate or not, contrary to the longstanding attempts in showing how the macroscopic nature of probe detection provokes state reduction. 1.

Related papers

Quantum State Reduction: An Operational Approach

Ozawa, M

A rigorous theory of quantum state reduction, the state change of the measured system caused by a measurement conditional upon the outcome of measurement, is developed fully within quantum mechanics without leading to the vicious circle relative to the von Neumann chain. For the basis of the theory, the local measurement theorem provides the joint probability distribution for the outcomes of local successive measurements on a noninteracting entangled system without assuming the projection postulate, and the quantum Bayes principle enables us to determine operationally the quantum state from a given information on the outcome of measurement.

•Jan 1, 1998•12 citations

Quantum State Reduction: An Operational Approach

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A rigorous theory of quantum state reduction, the state change of the measured system caused by a measurement conditional upon the outcome of measurement, is developed fully within quantum mechanics without leading to the vicious circle relative to the von Neumann chain. For the basis of the theory, the local measurement theorem provides the joint probability distribution for the outcomes of local successive measurements on a noninteracting entangled system without assuming the projection postulate, and the quantum Bayes principle enables us to determine operationally the quantum state from a given information on the outcome of measurement.

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Objective state reduction from microscopic irreversibility

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A realistic model of a projective quantum measurement is presented that provides a physical justification for the collapse postulate without invoking the macroscopic nature of a detector. The analysis adopts a minimally realist interpretation of the formalism, in which objective reality is ascribed only to quantum states associated with definite, empirically accessible physical properties. It is shown that objective state reduction arises from an irreversible microscopic process, enforced by appropriate boundary conditions, while the subsequent amplification stage merely reveals, at the macroscopic scale, the randomly selected measurement outcome.

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The Problem of Measurement and the Theory of Quantum State Reduction

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A new approach to the problem of measurement in quantum mechanics is proposed. In this approach, the process of measurement is described in the Heisenberg picture and divided into two stages. The first stage is to transduce the measured observable to the probe observable. The second stage is to amplify the probe observable to the macroscopic meter observable. Quantum state reduction is derived, based on the quantum Bayes principle, from the object-apparatus interaction in the first stage. The dynamical process of the second stage is described as a quantum amplification with infinite gain based on nonstandard analysis.

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Previous work has shown that the problem of measurement in quantum mechanics is not correctly seen as one of understanding some allegedly univocal process of measurement in nature which corresponds to the projection postulate. The present paper introduces a new perspective by showing that how we are to understand the nature of the change of quantum mechanical state on measurement depends very sensitively on the interpretation of the state function, and by showing how attention to this dependence can greatly sharpen the problems and relations between them. In particular, the problems take a form resembling their traditional formulation only on an inexact value interpretation, according to which the state function attributes inexact values of quantities to systems. On other interpretations we can apply (with various drawbacks) the subensemble idea, according to which a discontinuous change of quantum mechanical description results on measurement simply because we need a new state function to describe a new object.

Philosophy of Science•Sep 1, 1984•6 citations

The Measurement Problem Dissolved: Why Definite Outcomes Require No Collapse Postulate

Marcus Schmieke

The quantum measurement problem—why and how the deterministic, unitary evolution of quantum states gives rise to definite, stochastic outcomes—has remained unresolved since the inception of quantum mechanics. This paper proposes that wave function reduction is not a separate physical process requiring its own postulate, but an instance of Level-0 projection within the Quantum Blueprint Formalism (QBF). The QBF Level-0 framework describes the constrained transition from a pre-coherent space M_s of distinction configurations to a coherence manifold M_Θ of macroscopic order parameters, governed by three admissibility conditions: local compatibility (A1), preserved Heisenberg structure (A2), and bounded compression (A3). We demonstrate that quantum state reduction exhibits the same formal structure: it is a constrained projection from Hilbert space (possibility space) to eigenstate space (actuality space), subject to conditions structurally isomorphic to (A1)–(A3).

•Feb 11, 2026•0 citations
An operational approach to quantum state reduction, the state change of the measured system caused by a measurement of an observable conditional upon the outcome of measurement, is founded without assuming the projection postulate in any stages of the measuring process. Whereas the conventional formula assumes that the probe measurement satisfies the projection postulate, a new formula for determining the state reduction shows that the state reduction does not depend on how the probe observable is measured, or in particular does not depend on whether the probe measurement satisfies the projection postulate or not, contrary to the longstanding attempts in showing how the macroscopic nature of probe detection provokes state reduction. 1.
A rigorous theory of quantum state reduction, the state change of the measured system caused by a measurement conditional upon the outcome of measurement, is developed fully within quantum mechanics without leading to the vicious circle relative to the von Neumann chain. For the basis of the theory, the local measurement theorem provides the joint probability distribution for the outcomes of local successive measurements on a noninteracting entangled system without assuming the projection postulate, and the quantum Bayes principle enables us to determine operationally the quantum state from a given information on the outcome of measurement.
A rigorous theory of quantum state reduction, the state change of the measured system caused by a measurement conditional upon the outcome of measurement, is developed fully within quantum mechanics without leading to the vicious circle relative to the von Neumann chain. For the basis of the theory, the local measurement theorem provides the joint probability distribution for the outcomes of local successive measurements on a noninteracting entangled system without assuming the projection postulate, and the quantum Bayes principle enables us to determine operationally the quantum state from a given information on the outcome of measurement.
A realistic model of a projective quantum measurement is presented that provides a physical justification for the collapse postulate without invoking the macroscopic nature of a detector. The analysis adopts a minimally realist interpretation of the formalism, in which objective reality is ascribed only to quantum states associated with definite, empirically accessible physical properties. It is shown that objective state reduction arises from an irreversible microscopic process, enforced by appropriate boundary conditions, while the subsequent amplification stage merely reveals, at the macroscopic scale, the randomly selected measurement outcome.
A new approach to the problem of measurement in quantum mechanics is proposed. In this approach, the process of measurement is described in the Heisenberg picture and divided into two stages. The first stage is to transduce the measured observable to the probe observable. The second stage is to amplify the probe observable to the macroscopic meter observable. Quantum state reduction is derived, based on the quantum Bayes principle, from the object-apparatus interaction in the first stage. The dynamical process of the second stage is described as a quantum amplification with infinite gain based on nonstandard analysis.
Previous work has shown that the problem of measurement in quantum mechanics is not correctly seen as one of understanding some allegedly univocal process of measurement in nature which corresponds to the projection postulate. The present paper introduces a new perspective by showing that how we are to understand the nature of the change of quantum mechanical state on measurement depends very sensitively on the interpretation of the state function, and by showing how attention to this dependence can greatly sharpen the problems and relations between them. In particular, the problems take a form resembling their traditional formulation only on an inexact value interpretation, according to which the state function attributes inexact values of quantities to systems. On other interpretations we can apply (with various drawbacks) the subensemble idea, according to which a discontinuous change of quantum mechanical description results on measurement simply because we need a new state function to describe a new object.
The quantum measurement problem—why and how the deterministic, unitary evolution of quantum states gives rise to definite, stochastic outcomes—has remained unresolved since the inception of quantum mechanics. This paper proposes that wave function reduction is not a separate physical process requiring its own postulate, but an instance of Level-0 projection within the Quantum Blueprint Formalism (QBF). The QBF Level-0 framework describes the constrained transition from a pre-coherent space M_s of distinction configurations to a coherence manifold M_Θ of macroscopic order parameters, governed by three admissibility conditions: local compatibility (A1), preserved Heisenberg structure (A2), and bounded compression (A3). We demonstrate that quantum state reduction exhibits the same formal structure: it is a constrained projection from Hilbert space (possibility space) to eigenstate space (actuality space), subject to conditions structurally isomorphic to (A1)–(A3).