Friday, June 22, 2012

1206.4945 (V. Bergholm et al.)

How to Transfer between Arbitrary $n$-Qubit Quantum States by Coherent
Control and Simplest Switchable Noise on a Single Qubit
   [PDF]

V. Bergholm, T. Schulte-Herbrueggen
We explore reachable sets of open n-qubit quantum systems the coherent parts of which are under full unitary control and that have just one qubit whose unital or non-unital noise amplitudes can be modulated in time such as to provide an additional degree of incoherent control. In particular, adding bang-bang control of amplitude damping noise (non-unital) allows the dynamic system to act transitively on the entire set of density operators. This means one can transform any initial quantum state into any desired target state. Adding switchable bit-flip noise (unital), on the other hand, suffices to explore all states majorised by the initial state. We have extended our optimal control algorithm (DYNAMO package) by degrees of incoherent control so that these unprecedented reachable sets can systematically be exploited for experimental settings. Numerical results are compared to constructive analytical schemes.
View original: http://arxiv.org/abs/1206.4945

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