Retrodiction for optical attenuators, amplifiers, and detectors

Ottavia Jedrkiewicz, Rodney Loudon, John Jeffers

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The transformation that an attenuator makes on the state of an optical field is the time reverse of that of an amplifier. Thus predicting the output state for an amplifier is equivalent to retrodicting the input state of an attenuator. We explore the consequences of this equivalence for simple optical quantum communication channels. One counterintuitive consequence is that the mean number of photons sent into an amplifier as retrodicted from a measurement of the number of output photons does not include the contribution of the amplifier noise.
Original languageEnglish
Pages (from-to)033805-1
Number of pages33804
JournalPhysical Review A
Issue number3
Publication statusPublished - Sept 2004


  • optics
  • attenuator
  • amplifier
  • detector
  • quantum physics
  • photonics


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