Unambiguous unitary quantum channels

  • Authors:

  • Shengjun Wu;Xuemei Chen

  • Affiliations:

  • Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, P. R. China;Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, P. R. China

  • Venue:
  • Quantum Information & Computation
  • Year:
  • 2007

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Abstract

Unambiguous unitary maps and unambiguous unitary quantum channels are introducedand some of their properties are derived. These properties ensure certain simple form forthe measurements involved in realizing an unambiguous unitary quantum channel. Errorcorrection and unambiguous error correction with nonzero probability are discussed interms of unambiguous unitary quantum channels. We not only re-derive the well-knowncondition for a set of errors to be correctable with certainty, but also obtain a necessaryand suffcient condition for the errors caused by a noisy channel to be correctable withany nonzero probability. Dense coding with a partially entangled state can also beviewed as an unambiguous unitary quantum channel when all messages are required tobe transmitted with equal probability of success, the maximal achievable probability ofsuccess is derived and the optimum protocol is also obtained.