Volume 77, Number 4, February 2007
|Number of page(s)||5|
|Published online||05 February 2007|
Entropic information-disturbance tradeoff
QUIT, Quantum Information Theory Group, Dipartimento di Fisica “A. Volta”, Università di Pavia - via A. Bassi 6, I-27100 Pavia, Italy
Accepted: 14 December 2006
We show the flaws found in the customary fidelity-based definitions of disturbance in quantum measurements and evolutions. We introduce the “entropic disturbance" D and show that it adequately measures the degree of disturbance, intended essentially as an irreversible change in the state of the system. We also find that it complies with an information-disturbance tradeoff, namely the mutual information between the eigenvalues of the initial state and the measurement results is less than or equal to D.
PACS: 03.67.-a – Quantum information / 03.65.Yz – Decoherence; open systems; quantum statistical methods / 03.65.Ta – Foundations of quantum mechanics; measurement theory
© Europhysics Letters Association, 2007
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