Critique of protective measurements

Dass, N. D. Hari; Qureshi, Tabish

doi:10.1103/physreva.59.2590

Cited by 33 publications

(51 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…II E of Ref. [4]). A spin-1 2 particle travels through a uniform magnetic field of unknown direction and magnitude.…”

Section: Measurement Modelmentioning

confidence: 99%

“…In a protective measurement [1][2][3][4][5], the quantum system interacts weakly with a measuring apparatus via an interaction Hamiltonian given bŷ…”

Section: Measurement Modelmentioning

confidence: 99%

“…This paradigmatic and experimentally relevant model was first studied in Refs. [1,4], but those studies merely demonstrated one basic feature of protective measurement, namely, how information about the expectation value becomes encoded in the shift of the apparatus pointer. The studies only considered in the limit of an infinitesimally weak inhomogeneous magnetic field applied for an infinite amount of time (and infinitely rapidly turned on and off), without attending to the crucial issue of state disturbance.…”

Section: Introductionmentioning

confidence: 99%

“…Besides being an important and unusual instance of a quantum measurement, protective measurement offers the possibility of successively carrying out measurements of expectation values of different observables while the system is likely to remain in its initial quantum state. This state may then be reconstructed from the measured expectation values with in principle arbitrarily high fidelity [1][2][3][4]. In this way, protective measurement may provide a route toward state tomography of single quantum systems.…”

Section: Introductionmentioning

confidence: 99%

“…Protective measurement [1][2][3][4][5][6] is a scheme for measuring expectation values of a quantum system in a way that makes this state disturbance arbitrarily small. For such a measurement to obtain, the system is coupled weakly to the apparatus, and the initial state of the system is required to be in a nondegenerate eigenstate of its Hamiltonian.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Analysis of quantum-state disturbance in a protective measurement of a spin-1/2 particle

Schlosshauer

2015

Phys. Rev. A

View full text Add to dashboard Cite

A distinguishing feature of protective measurement is the possibility of obtaining information about expectation values while making the disturbance of the initial state arbitrarily small. Quantifying this state disturbance is of paramount importance. Here we derive exact and perturbative expressions for the state disturbance and the faithfulness of the measurement outcome in a model describing a spin-1 2 particle protectively measured by an inhomogeneous magnetic field. We determine constraints on the experimentally required field strengths from bounds imposed on the allowable state disturbance. We also demonstrate that the protective measurement may produce an incorrect result even when the particle's spin state is unaffected by the measurement, and show that successive measurements using multiple magnetic fields produce the same state disturbance as a single measurement involving a superposition of these fields. Our results supply comprehensive understanding of a paradigmatic model for protective measurement, may aid the experimental implementation of the measurement scheme, and illustrate fundamental properties of protective measurements.Journal reference: Phys. Rev. A 92, 062116 (2015),

show abstract

“…II E of Ref. [4]). A spin-1 2 particle travels through a uniform magnetic field of unknown direction and magnitude.…”

Section: Measurement Modelmentioning

confidence: 99%

“…In a protective measurement [1][2][3][4][5], the quantum system interacts weakly with a measuring apparatus via an interaction Hamiltonian given bŷ…”

Section: Measurement Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Analysis of quantum-state disturbance in a protective measurement of a spin-1/2 particle

Schlosshauer

2015

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

Bibliography

2001

Quantum Measurement of a Single System

View full text Add to dashboard Cite

Meaning of the wave function

Gao

2011

Int J of Quantum Chemistry

View full text Add to dashboard Cite

We investigate the meaning of the wave function by analyzing the mass and charge density distributions of a quantum system. According to protective measurement, a charged quantum system has mass and charge density distributing in space, proportional to the modulus square of its wave function. In a realistic interpretation, the wave function of a quantum system can be taken as a description of either a physical field or the ergodic motion of a particle. If the wave function is a physical field, then the mass and charge density will be distributed throughout space at a given time for a charged quantum system, and thus there will exist gravitational and electrostatic self-interactions of its wave function. This not only violates the superposition principle of quantum mechanics but also contradicts experimental observations. Thus the wave function cannot be a description of a physical field but a description of the ergodic motion of a particle. For the later there is only a localized particle with mass and charge at every instant, and thus there will not exist any self-interaction for the wave function. It is further argued that the classical ergodic models, which assume continuous motion of particles, cannot be consistent with quantum mechanics. Based on the negative result, we suggest that the wave function is a description of the quantum motion of particles, which is random and discontinuous in nature. On this interpretation, the modulus square of the wave function not only gives the density of probability of the particle being found in certain locations, but also gives the density of objective probability of the particle being there. We show that this new interpretation of the wave function provides a natural realistic alternative to the orthodox interpretation, and its implications for other realistic interpretations of quantum mechanics are also briefly discussed.Comment: 22 page

show abstract

Critique of protective measurements

Cited by 33 publications

References 19 publications

Analysis of quantum-state disturbance in a protective measurement of a spin-1/2 particle

Analysis of quantum-state disturbance in a protective measurement of a spin-1/2 particle

Bibliography

Meaning of the wave function

Contact Info

Product

Resources

About