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Ancilla models for quantum operations: for what unitaries does the ancilla state have to be physical?

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Abstract

Any evolution described by a completely positive trace-preserving linear map can be imagined as arising from the interaction of the evolving system with an initially uncorrelated ancilla. The interaction is given by a joint unitary operator, acting on the system and the ancilla. Here we study the properties such a unitary operator must have in order to force the choice of a physical—that is, positive—state for the ancilla if the end result is to be a physical—that is, completely positive—evolution of the system.

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Authors and Affiliations

  1. Center for Quantum Information and Control, University of New Mexico, MSC07-4220, Albuquerque, NM, 87131-0001, USA

    Zhang Jiang & Carlton M. Caves

  2. Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada

    Marco Piani

  3. Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Brisbane, 4072, Australia

    Carlton M. Caves

Authors
  1. Zhang Jiang
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  2. Marco Piani
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  3. Carlton M. Caves
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Correspondence to Zhang Jiang.

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Jiang, Z., Piani, M. & Caves, C.M. Ancilla models for quantum operations: for what unitaries does the ancilla state have to be physical?. Quantum Inf Process 12, 1999–2017 (2013). https://doi.org/10.1007/s11128-012-0500-x

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  • DOI: https://doi.org/10.1007/s11128-012-0500-x

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