Properties of local quantum operations with shared entanglement

  • Authors:
  • Gus Gutoski

  • Affiliations:
  • Institute for Quantum Computing and School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada

  • Venue:
  • Quantum Information & Computation
  • Year:
  • 2009

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Abstract

Multi-party local quantum operations with shared quantum entanglement or sharedclassical randomness are studied. The following facts are established:• There is a ball of local operations with shared randomness lying within the spacespanned by the no-signaling operations and centred at the completely noisy channel.• The existence of the ball of local operations with shared randomness is employedto prove that the weak membership problem for local operations with sharedentanglement is strongly NP-hard.• Local operations with shared entanglement are characterized in terms of linearfunctionals that are "completely" positive on a certain cone K of separable Hermitianoperators, under a natural notion of complete positivity appropriate tothat cone. Local operations with shared randomness (but not entanglement) arealso characterized in terms of linear functionals that are merely positive on thatsame cone K.• Existing characterizations of no-signaling operations are generalized to the multipartysetting and recast in terms of the Choi-Jamio lkowski representation forquantum super-operators. It is noted that the standard nonlocal box is an exampleof a no-signaling operation that is separable, yet cannot be implemented by localoperations with shared entanglement.