2006/11/11 by Subhashish Banerjee, R Ghosh, R. Ghosh · 2 citations
Computer Science · Physics and Astronomy · #Context (archaeology) #Mechanical and Optical Resonators #Observable #Propagator #Quantum #Quantum Information and Cryptography #Quantum optics and atomic interactions #Quantum state #Quantum system #Rotation (mathematics) #quant-ph
paper · pdf · doi:10.1088/1751-8113/40/6/006
published as J. Phys. A: Math. Theo. 40, 1273 (2007) · 16 pages, no figures
arxiv created 2006/11/11 · openalex publication_date 2007/01/23 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
In the scheme of a quantum nondemolition (QND) measurement, an observable is measured without perturbing its evolution. In the context of studies of decoherence in quantum computing, we examine the 'open' quantum system of a two-level atom or, equivalently, a spin-1/2 system, in interaction with quantum reservoirs of either oscillators or spins, under the QND condition of the Hamiltonian of the system commuting with the system–reservoir interaction. For completeness, we also examine the well-known non-QND spin-Bose problem. For all these many-body systems, we use the methods of functional integration to work out the propagators. The propagators for the QND Hamiltonians are shown to be analogous to the squeezing and rotation operators, respectively, for the two kinds of baths considered. Squeezing and rotation being both phase-space area-preserving canonical transformations, this brings out an interesting connection between the energy-preserving QND Hamiltonians and the homogeneous linear canonical transformations.