A No-summoning theorem in Relativistic Quantum Theory

TL;DR

This paper introduces a no-summoning theorem in relativistic quantum theory, showing fundamental limits on retrieving unknown quantum states in Minkowski space-time, which differ from classical and non-relativistic cases.

Contribution

It establishes a new no-summoning theorem that combines no-signalling and no-cloning principles, revealing intrinsic constraints in relativistic quantum information.

Findings

Quantum states cannot be summoned in Minkowski space-time.

Classical states can be summoned arbitrarily quickly.

The theorem is rooted in fundamental principles of relativistic quantum theory.

Abstract

Alice gives Bob an unknown localized physical state at some point P. At some point Q in the causal future of P, Alice will ask Bob for the state back. Bob knows this, but does not know at which point Q until the request is made. Bob can satisfy Alice's summons, with arbitrarily short delay, for a quantum state in Galilean space-time or a classical state in Minkowski space-time. However, given an unknown quantum state in Minkowski space-time, he cannot generally fulfil her summons. This {\it no-summoning theorem} is a fundamental feature of, and intrinsic to, relativistic quantum theory. It follows from the no-signalling principle and the no-cloning theorem, but not from either alone.