Information-disturbance tradeoff in sending Direction information via antiparallel quantum spin

TL;DR

This paper derives the optimal tradeoff between information gain and disturbance when sending direction information using antiparallel quantum spins, providing bounds relevant for quantum communication security.

Contribution

It establishes the optimal information-disturbance tradeoff bound for antiparallel spins and identifies measurements that achieve this bound.

Findings

Derived the optimal tradeoff bound for antiparallel spins

Identified quantum measurements that attain the bound

Compared bounds for antiparallel and parallel spins

Abstract

For sending unknown direction information, antiparallel spins contains more direction information than parallel spins(Gisin and Popescu, 1999, \textit{Phys. Rev. Lett.} 83, 432).In this paper, the optimal information-disturbance tradeoff bound for antiparallel spins is derived. The quantum measurements which attain the optimal tradeoff bound are obtained. This result can be of practical relevance for posing some general limits on Eve's eavesdropping process. Finally, we also present a comparison between the bound for antiparallel spins and the bound for parallel spins.