Quantum bit commitment and the reality of the quantum state

TL;DR

This paper explores how relaxing certain assumptions in quantum bit commitment protocols can lead to secure schemes and argues that the security of such protocols supports the reality of the quantum state, assuming no retrocausality.

Contribution

It introduces a secure quantum bit commitment protocol that relaxes key assumptions and links protocol security to the reality of the quantum state without ontological commitments.

Findings

Relaxing assumptions prevents Alice's steering attacks.

A secure protocol is demonstrated in a teleportation setting.

Security implies the reality of the quantum state, excluding retrocausality.

Abstract

Quantum bit commitment (QBC) is insecure in the standard non-relativistic quantum cryptographic framework, essentially because Alice can exploit quantum steering to defer making her commitment. Two assumptions in this framework are that: (a) Alice knows the ensembles of evidence $E$ corresponding to either commitment; and (b) system $E$ is quantum rather than classical. Here, we show how relaxing assumption (a) or (b) can render her malicious steering operation indeterminable or inexistent, respectively. Finally, we present a secure protocol that relaxes both assumptions in a quantum teleportation setting. Without appeal to an ontological framework, we argue that the protocol's security entails the reality of the quantum state, provided retrocausality is excluded.