A no-summoning theorem in relativistic quantum theory

  • Authors:

  • Adrian Kent

  • Affiliations:

  • Centre for Quantum Information and Foundations, DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge, UK CB3 0WA and Perimeter Institute for Theoretical Physics, Waterloo, C ...

  • Venue:
  • Quantum Information Processing
  • Year:
  • 2013

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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 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.