Unambiguous discrimination between mixed quantum states based on programmable quantum state discriminators

TL;DR

This paper investigates the limits of unambiguous programmable discrimination of mixed quantum states, proving the non-existence of a universal discriminator with certain registers and proposing an alternative approach that improves success probability in specific cases.

Contribution

It establishes the non-existence of a universal unambiguous programmable discriminator with two program and one data register for mixed states and introduces an alternative method that enhances discrimination success.

Findings

Universal discriminator with two program and one data register does not exist.

Proposed method improves success probability when reaching the upper bound.

The approach outperforms traditional methods in certain special cases.

Abstract

We discuss the problem of designing an unambiguous programmable discriminator for mixed quantum states. We prove that there does not exist such a universal unambiguous programmable discriminator for mixed quantum states that has two program registers and one data register. However, we find that we can use the idea of programmable discriminator to unambiguously discriminate mixed quantum states. The research shows that by using such an idea, when the success probability for discrimination reaches the upper bound, the success probability is better than what we do not use the idea to do, except for some special cases.