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arXiv · 1203.4977

Fighting Decoherence by Feedback-controlled Dissipation

Gernot Schaller
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Abstract

Repeated closed-loop control operations acting as piecewise-constant Liouville superoperators conditioned on the outcomes of regularly performed measurements may effectively be described by a fixed-point iteration for the density matrix. Even when all Liouville superoperators point to the completely mixed state, feedback of the measurement result may lead to a pure state, which can be interpreted as selective dampening of undesired states. Using a microscopic model, we exemplify this for a single qubit, which can be purified in an arbitrary single-qubit state by tuning the measurement direction and two qubits that may be purified towards a Bell state by applying a special 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.

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Gernot Schaller. 2012-06-12. Fighting Decoherence by Feedback-controlled Dissipation. https://doi.org/10.1103/physreva.85.062118

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