Chennai Mathematical Institute

Seminars




Phase Distributions in Open Quantum Systems
Subhashish Banerjee
Raman Research Institute, Bangalore.
20-02-08


Abstract

We motivate and discuss the quantum description of phases using phase distributions in open quantum systems. Open quantum systems can be broadly classified into two categories: (A). Quantum non-demolition (QND), which involves decoherence without any dissipation and (B). Quantum dissipative systems, where decoherence is accompanied with dissipation. In the parlance of quantum information theory, the noise generated by a QND open system would be a ``phase damping channel'', while that generated by a dissipative (Lindblad) evolution would be a ``(generalized) amplitude damping channel''. A brief description of the underlying dynamics of QND as well as quantum dissipative processes is provided and their connection to quantum information processes detailed. We then provide a unified description of phases for both QND as well as dissipative systems, starting from a number of interesting initial conditions of practical relevance, using the phase distribution approach. The phase distributions conditioned on various initial system states are used to study the corresponding phase dispersion, a measure of quantum phase fluctuations and also used to discuss the `number-phase' complementarity for atomic systems.





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