We prove tight entropic uncertainty relations for a large number of mutually unbiased measurements. In particular, we show that a bound derived from the result by Maassen and Uffink for 2 such measurements can in fact be tight for up to sqrt{d} measurements in mutually unbiased bases. We then show that using more mutually unbiased bases does not always lead to a better locking effect. We prove that the optimal bound for the accessible information using up to sqrt{d} specific mutually unbiased bases is log d/2, which is the same as can be achieved by using only two bases. Our result indicates that merely using mutually unbiased bases is not sufficient to achieve a strong locking effect, and we need to look for additional properties.
American Physical Society
Physical Review A: Atomic, Molecular and Optical Physics
Quantum Information Processing
Quantum Computing and Advanced System Research

Wehner, S.D.C, & Ballester Sanches, M.A. (2007). Entropic uncertainty relations and locking: tight bounds for mutually unbiased bases. Physical Review A: Atomic, Molecular and Optical Physics, 75, 22319–02last.