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Optimal quantum-programmable projective measurement with linear optics

Research output: Contribution to journalArticle

  • Ulysse Chabaud
  • Eleni Diamanti
  • Damian Markham
  • Elham Kashefi
  • Antoine Joux

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Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalPhysical Review A
Issue number6
Publication statusPublished - 14 Dec 2018


We present a scheme for a universal device which can be programed by quantum states to approximate a chosen projective measurement to a given precision. Our scheme can be viewed as an extension of the swap test to the instance where one state is supplied many times. As such, it has many potential applications given the variety of quantum information tasks which make use of the swap test. In particular, we show that our scheme is optimal for state discrimination under the one-sided error requirement, and optimally approximates any projective measurement. Furthermore, we propose a practical implementation of our scheme with passive linear optics, which involves a simple interferometer composed only of balanced beam splitters.

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