Entanglement, decoherence, and dynamics of a two-state system

Abstract

Entanglement and decoherence arguably define the central issues of concern in present day quantum information theory. Decoherence occurs when a system interacts with its environment in an irreversible way; this prevents the quantum superposition of the system + environment's wavefunction from interfering with each other. A better understanding of environment-induced destruction of coherent superposition states is needed, as well as a clear description of the degree of entanglement between the quantum system and its environment. We quantitatively establish a correspondence between entanglement, decoherence, and spin dynamics for a two-state system coupled to a bath of harmonic oscillators, resulting in the celebrated spin-boson model. Applications to solid-state and cold atomic systems are also discussed.

Keywords:

• entanglement
• decoherence
• spin-boson model
• spin dynamics

Acknowledgements

We acknowledge discussions with M. Büttiker, L. Glazman, W. Hofstetter, A. Imambekov, P.P. Orth, and D. Roosen. This work is supported by NSF through DMR-0803200 and through the Center for Quantum Information Physics (DMR-0653377), by DOE under the contract DE-FG02-08ER46541, and by YINQE.