Friday, March 23, 2012

1203.4977 (Gernot Schaller)

Fighting Decoherence by Feedback-controlled Dissipation    [PDF]

Gernot Schaller
Repeated closed-loop control operations acting as piecewise-constant Liouville superoperators may effectively be described by a fixed-point iteration for the density matrix. Under appropriate parameter choices, its stationary point corresponds to a pure state, which is achieved by selective dampening of undesired states. We exemplify this for a single qubit, which can be purified by tuning the measurement direction and two qubits that may be purified towards a Bell state by applying a continuous two-local measurement. The method does not require precise knowledge of decoherence channels and works for large reservoir temperatures provided measurement, processing, and control can be implemented in a continuous fashion.
View original: http://arxiv.org/abs/1203.4977

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