Universal discriminator for completely unknown optical qubits

TL;DR

This paper introduces an optical setup capable of unambiguously discriminating any pair of unknown single photon polarization qubits using linear optics and non-linear elements, achieving optimal discrimination without prior knowledge.

Contribution

The paper presents a novel experimental scheme that can perfectly discriminate any two unknown polarization qubits using a combination of linear and non-linear optical components.

Findings

Achieves unambiguous discrimination of unknown qubits

Uses optical CNOT gates and Kerr non-linearities

Provides a deterministic processing method

Abstract

We propose an experimental setup that is capable of unambiguously discriminating any pair of linearly independent single photon polarization qubits, about which we don't have any knowledge except that an extra pair of these unknown states are provided as the reference. This setup, which is constructed with optical CNOT gates, weak cross Kerr non-linearities, Bell state analysers and other linear optical elements, transforms the unknown triple photon input states to the corresponding single photon states to be deterministically processed by linear optics circuit. The optimal discrimination of the unknown states is achieved by this setup.