Localized closed timelike curves can perfectly distinguish quantum states

TL;DR

This paper demonstrates that qubits on closed timelike curves can perfectly distinguish quantum states, enabling the violation of fundamental quantum limits and compromising quantum cryptography protocols.

Contribution

It introduces the use of localized closed timelike curves as a resource for perfect quantum state discrimination, revealing new implications for quantum information security.

Findings

Closed timelike curves enable perfect quantum state discrimination

They can break quantum key distribution protocols

They allow violation of the Holevo bound

Abstract

We show that qubits traveling along closed timelike curves are a resource that a party can exploit to distinguish perfectly any set of quantum states. As a result, an adversary with access to closed timelike curves can break any prepare-and-measure quantum key distribution protocol. Our result also implies that a party with access to closed timelike curves can violate the Holevo bound.