A generalized unknown qubit discriminator

TL;DR

This paper presents a quantum state discriminator capable of unambiguously distinguishing between two unknown qubits using multiple copies, achieving optimal performance with different measurement strategies depending on input probabilities, and simplifying to von Neumann measurements with large program registers.

Contribution

It introduces a generalized discriminator for unknown qubits that optimizes measurement strategies based on input probabilities and register size, advancing quantum state discrimination techniques.

Findings

Achieves optimal unambiguous discrimination with von Neumann and POVM measurements.

Performance varies with input preparation probabilities.

Large program registers allow reduction to von Neumann measurements.

Abstract

We discuss a state discriminator that unambiguously distinguishes between two quantum registers prepared with multiple copies of two unknown qubits. This device achieves the optimal performance by von Neumann measurement and general POVM in different ranges of the input preparation probabilities, respectively, and in the limit of very large program registers the optimal measurement reduces to only von Neumann measurements.