Quantum optical state comparison amplification of coherent states

Ugo Zanforlin, Ross J. Donaldson, Luca Mazzarella, Robert J. Collins, John Jeffers, Gerald S. Buller

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

1 Citation (Scopus)
20 Downloads (Pure)


As light propagates through a transmission media, such as an optical fiber, it experiences a length-dependent loss which can reduce the communication efficiency as the transmission distance increases. In conventional telecommunications, optical signals can be transmitted over inter-continental distances, due to deterministic all-optical amplifiers. However, quantum communications are still limited to transmission distances of typically a few 100's km since deterministic amplifiers cannot be used to amplify quantum signals. The use of deterministic amplification on a quantum signal will introduce noise that will mask the original quantum properties of the signal, introducing uncertainty or errors to any measurement. Nondeterministic methods for amplifying quantum signals via post-selection can be used instead, providing a solution to create a low noise quantum amplifier. Several methods for nondeterministic amplification have already been experimentally demonstrated. However, these devices rely on "quantum resources" which makes implementation challenging. Here we present an overview of experimental demonstrations for amplifying coherent states using a method called state comparison amplification. This is a nondeterministic protocol that performs amplification of known sets of phase-encoded coherent states using two modular stages. The outcome of each stage is recorded using single-photon detectors and time-stamped electronics to enable post-selection. State comparison amplification is a relatively simple technique, only requiring "off-the-shelf" components. The presentation will show several demonstrations of state comparison amplification including an amplifier which has high gain, fidelity, and success rate with the added advantage of being robust to channel noise and easily reconfigurable. Finally, we will discuss the effect of introducing a feedforward mechanism allowing for unsuccessful state amplifications.

Original languageEnglish
Title of host publicationQuantum Technologies 2018
EditorsJürgen Stuhler, Andrew J. Shields, Miles J. Padgett
Place of PublicationBellingham, Washington
Number of pages11
ISBN (Electronic)9781510618749
Publication statusPublished - 29 May 2018
EventQuantum Technologies 2018 - Strasbourg, France
Duration: 23 Apr 201825 Apr 2018


ConferenceQuantum Technologies 2018


  • coherent states
  • optical amplifier
  • probabilistic amplifier
  • quantum amplifier
  • quantum technologies
  • state amplification
  • state comparison


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