# Macroscopic Observables

@article{Poulin2004MacroscopicO, title={Macroscopic Observables}, author={D. Poulin}, journal={Physical Review A}, year={2004} }

We study macroscopic observables defined as the total value of a physical quantity over a collection of quantum systems. We show that previous results obtained for an infinite ensemble of identically prepared systems lead to incorrect conclusions for finite ensembles. In particular, exact measurement of a macroscopic observable significantly disturbs the state of any finite ensemble. However, we show how this disturbance can be made arbitrarily small when the measurements are of finite accuracy… Expand

#### 26 Citations

Robust Macroscopic Quantum Measurements in the Presence of Limited Control and Knowledge

- Physics, Medicine
- Entropy
- 2018

This paper focuses on the task of the polarization direction estimation of a system of N spins 1/2 particles and investigates the model some of us proposed in Barnea et al., 2017, based on a von Neumann pointer measurement, and shows traits of a classical measurement for an intermediate coupling strength. Expand

Coherence, asymmetry, and quantum macroscopicity

- Physics
- 2018

We investigate a measure of quantum coherence and its extension to quantify quantum macroscopicity. The coherence measure can also quantify the asymmetry of a quantum state with respect to a given… Expand

Quantum averages of weak values

- Physics
- 2005

We re-examine the status of the weak value of a quantum mechanical observable as an objective physical concept, addressing its physical interpretation and general domain of applicability. We show… Expand

Classical world arising out of quantum physics under the restriction of coarse-grained measurements.

- Physics, Medicine
- Physical review letters
- 2007

It is demonstrated that for unrestricted measurement accuracy, no classical description is possible for arbitrarily large systems and for a certain time evolution that under coarse-grained measurements, not only macrorealism but even classical Newtonian laws emerge out of the Schrödinger equation and the projection postulate. Expand

Conditions for quantum violation of macroscopic realism.

- Physics, Medicine
- Physical review letters
- 2008

There exist "nonclassical" Hamiltonians whose time evolution cannot be understood classically, although at every instant of time the quantum state appears as a classical mixture, and it is suggested that such Hamiltonians are unlikely to be realized in nature because of their high computational complexity. Expand

Quantum Models of Classical World

- Physics, Computer Science
- Entropy
- 2013

This paper has two aims: a clear explanation of all new results and a coherent and contradiction-free account of the whole quantum mechanics including all necessary changes of its current textbook version. Expand

Correlations in local measurements and entanglement in many-body systems

- Physics
- 2018

While entanglement plays an important role in characterizing quantum many-body systems, it is hardly possible to directly access many-body entanglement in real experiments. In this paper, we study… Expand

Quantum Model of Classical Mechanics: Maximum Entropy Packets

- Mathematics, Physics
- 2009

In a previous paper, a statistical method of constructing quantum models of classical properties has been described. The present paper concludes the description by turning to classical mechanics. The… Expand

Disappearance of macroscopic superpositions in perfectly isolated systems by thermalization processes

- Physics
- 2016

Schr\"odinger's illustration of an imaginary cat in a box, neither alive nor dead, leads to a question of whether and how long a macroscopic quantum superposition can exist in various situations. It… Expand

Local realism of macroscopic correlations.

- Physics, Medicine
- Physical review letters
- 2011

It is argued that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that Macroscopic measurements do not reveal properties of individual particles. Expand

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