# Nonclassical dynamics induced by a quantum meter

## Abstract

Conventionally, the effect of measurements on a quantum system is assumed to introduce decoherence, which renders the system classical-like. We consider here a microscopic meter, that is, an auxiliary essentially quantum system whose state is measured repeatedly, and show that it can be employed to induce transitions from classical states into inherently quantumlike states. The meter state is assumed to be lost in the environment and we derive a non-Markovian master equation for the dynamic system in the case of nondemolition coupling to the meter; this equation can be cast in the form of an (N{sub a})th-order differential equation in time, where N{sub a} is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin-(1/2) meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.

- Authors:

- Laboratoire Aime Cotton, Universite Paris-Sud, 91405 Orsay Cedex (France)
- Laser Physics and Quantum Optics, Royal Institute of Technology (KTH), 10691 Stockholm (Sweden)
- (Finland)

- Publication Date:

- OSTI Identifier:
- 20786255

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physical Review. A; Journal Volume: 72; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevA.72.062104; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 74 ATOMIC AND MOLECULAR PHYSICS; COUPLING; DIFFERENTIAL EQUATIONS; HAMILTONIANS; HARMONIC OSCILLATORS; MARKOV PROCESS; QUANTUM MECHANICS; SPIN

### Citation Formats

```
Clausen, J., Akulin, V. M., Salo, J., Materials Physics Laboratory, Helsinki University of Technology, 02015 HUT, and Stenholm, S..
```*Nonclassical dynamics induced by a quantum meter*. United States: N. p., 2005.
Web. doi:10.1103/PHYSREVA.72.0.

```
Clausen, J., Akulin, V. M., Salo, J., Materials Physics Laboratory, Helsinki University of Technology, 02015 HUT, & Stenholm, S..
```*Nonclassical dynamics induced by a quantum meter*. United States. doi:10.1103/PHYSREVA.72.0.

```
Clausen, J., Akulin, V. M., Salo, J., Materials Physics Laboratory, Helsinki University of Technology, 02015 HUT, and Stenholm, S.. Thu .
"Nonclassical dynamics induced by a quantum meter". United States.
doi:10.1103/PHYSREVA.72.0.
```

```
@article{osti_20786255,
```

title = {Nonclassical dynamics induced by a quantum meter},

author = {Clausen, J. and Akulin, V. M. and Salo, J. and Materials Physics Laboratory, Helsinki University of Technology, 02015 HUT and Stenholm, S.},

abstractNote = {Conventionally, the effect of measurements on a quantum system is assumed to introduce decoherence, which renders the system classical-like. We consider here a microscopic meter, that is, an auxiliary essentially quantum system whose state is measured repeatedly, and show that it can be employed to induce transitions from classical states into inherently quantumlike states. The meter state is assumed to be lost in the environment and we derive a non-Markovian master equation for the dynamic system in the case of nondemolition coupling to the meter; this equation can be cast in the form of an (N{sub a})th-order differential equation in time, where N{sub a} is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin-(1/2) meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.},

doi = {10.1103/PHYSREVA.72.0},

journal = {Physical Review. A},

number = 6,

volume = 72,

place = {United States},

year = {Thu Dec 15 00:00:00 EST 2005},

month = {Thu Dec 15 00:00:00 EST 2005}

}