4 years ago

Quantifying Early Time Quantum Decoherence Dynamics through Fluctuations

Quantifying Early Time Quantum Decoherence Dynamics through Fluctuations
Ignacio Franco, Bing Gu
We introduce a general but simple relation between the timescale for quantum coherence loss and the initial fluctuations of operators that couple a quantum system with a surrounding bath. The relation allows the prediction and measurement of early time decoherence dynamics for any open quantum system, through purity, without reconstructing the system’s many-body density matrix. It is applied to predict the decoherence time for basic models—the Holstein chain, spin-boson and Caldeira-Legget models—commonly employed to capture electronic, vibrational, and vibronic dynamics in molecules. Such development also offers a practical platform to test the ability of approximate quantum dynamics methods to capture decoherence. In particular, a class of mixed quantum-classical schemes for molecular dynamics where the bath is treated classically, such as Ehrenfest dynamics, are shown to correctly capture short-time decoherence when the initial conditions are sampled from the Wigner distribution. These advances provide a useful platform to develop decoherence times for molecular processes and to test approximate molecular dynamics methods.

Publisher URL: http://dx.doi.org/10.1021/acs.jpclett.7b01817

DOI: 10.1021/acs.jpclett.7b01817

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