We have decided to discontinue the publication of preprints on our preprint server as of 1 March 2024. The publication culture within mathematics has changed so much due to the rise of repositories such as ArXiV (www.arxiv.org) that we are encouraging all institute members to make their preprints available there. An institute's repository in its previous form is, therefore, unnecessary. The preprints published to date will remain available here, but we will not add any new preprints here.
MiS Preprint
76/2019
Complete Characterization of Qubit Masking
Xiao-Bin Liang, Bo Li and Shao-Ming Fei
Abstract
We study the problem of information masking through nonzero linear operators that distribute information encoded in single qubits to the correlations between two qubits.
It is shown that a nonzero linear operator can not mask any nonzero measure set of qubit states. We prove that the maximal maskable set of states on the Bloch sphere with respect to any masker is the ones on a spherical circle. Any states on a spherical circle on the Bloch sphere are maskable, which also proves the conjecture on maskable qubit states given in [Phys. Rev. Lett. 120, 230501 (2018)].
Moreover, we provide explicitly operational unitary maskers for all maskable sets. As applications, new protocols for secret sharing are introduced.
