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CONSERVED QUANTITIES FOR THE DENSITY-MATRIX AND THE DEGREE OF STATISTICAL MIXING

RADMORE, PM; BARNETT, SM; STONEHAM, AM; (1990) CONSERVED QUANTITIES FOR THE DENSITY-MATRIX AND THE DEGREE OF STATISTICAL MIXING. PHYS SCRIPTA , 42 (2) 129 - 132. 10.1088/0031-8949/42/2/001. Green open access

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Abstract

We investigate the conserved quantities for a closed, N-state quantum system. A simple derivation from the equation of motion for the density matrix shows that there is an infinite number of such conserved quantities. However, only the first N of these constants of the motion are independent. These constants uniquely determine the degree of mixing in the system, which is itself conserved. We discuss the relationship between these results, the properties of Hamiltonians under unitary transformation and van Vleck's principle of spectroscopic stability.

Type: Article
Title: CONSERVED QUANTITIES FOR THE DENSITY-MATRIX AND THE DEGREE OF STATISTICAL MIXING
Open access status: An open access version is available from UCL Discovery
DOI: 10.1088/0031-8949/42/2/001
Publisher version: http://dx.doi.org/10.1088/0031-8949/42/2/001
Language: English
Additional information: Text made available to UCL Discovery by kind permission of IOP Publishing, 2012
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/184111
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