Volume 77, Number 4, February 2007
Article Number 40002
Number of page(s) 5
Section General
Published online 05 February 2007
EPL, 77 (2007) 40002
DOI: 10.1209/0295-5075/77/40002

Entropic information-disturbance tradeoff

L. Maccone

QUIT, Quantum Information Theory Group, Dipartimento di Fisica "A. Volta", Università di Pavia - via A. Bassi 6, I-27100 Pavia, Italy

received 19 September 2006; accepted in final form 14 December 2006; published February 2007
published online 5 February 2007

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.

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