Toward Vibration Measurement via Frequency-Entangled Two-Photon Interferometry

Spencer J. Johnson, Colin P. Lualdi, Andrew P. Conrad, Nathan T. Arnold, Michael Vayninger, Paul G. Kwiat

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


We present progress toward measuring nanometer-scale vibrations via a frequency-entangled two-photon interferometer. Unlike classical interference, two-photon – or Hong-Ou-Mandel – interference allows for optical metrology with resilience against imbalanced loss, dispersion, and optical background. However, the resolution of traditional degenerate frequency two-photon interference is limited by the photons’ bandwidths, requiring large bandwidths or long integration times to achieve nanometer-scale resolution. We have implemented a two-photon interferometer utilizing highly non-degenerate frequency-entangled photon pairs at 810 nm and 1550 nm, drastically increasing measurement sensitivity while retaining the advantages of two-photon interference. This enhancement comes via a beat note with frequency proportional to the photon detuning of 177 THz. The resulting measurement saturates the quantum Cramér-Rao bound, maximizing the information extracted per photon. We have demonstrated a measurement resolution of 2.3 nm with fewer than 18,000 detected photon pairs, orders of magnitude better than previous results. By reflecting one photon from the pair off a target surface, we may use our system to study small-scale vibrations.

Original languageEnglish (US)
Title of host publicationQuantum Sensing, Imaging, and Precision Metrology
EditorsJacob Scheuer, Selim M. Shahriar
ISBN (Electronic)9781510659995
StatePublished - 2023
EventQuantum Sensing, Imaging, and Precision Metrology 2023 - San Francisco, United States
Duration: Jan 28 2023Feb 2 2023

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceQuantum Sensing, Imaging, and Precision Metrology 2023
Country/TerritoryUnited States
CitySan Francisco


  • Frequency entanglement
  • precision sensing
  • two-photon interference

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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