Strong no-go theorem for Gaussian quantum bit commitment

TL;DR

This paper proves that unconditionally secure quantum bit commitment cannot be achieved with Gaussian states and operations, extending the no-go theorem to continuous-variable quantum protocols.

Contribution

It extends the quantum no-go theorem for bit commitment to Gaussian continuous-variable protocols, challenging a conjecture about quantum mechanics foundations.

Findings

Gaussian no-go theorem for quantum bit commitment

Incompatibility of Gaussian protocols with unconditionally secure bit commitment

Counter-example to the conjecture linking key distribution and bit commitment

Abstract

Unconditionally secure bit commitment is forbidden by quantum mechanics. We extend this no-go theorem to continuous-variable protocols where both players are restricted to use Gaussian states and operations, which is a reasonable assumption in current-state optical implementations. Our Gaussian no-go theorem also provides a natural counter-example to a conjecture that quantum mechanics can be rederived from the assumption that key distribution is allowed while bit commitment is forbidden in Nature.