A quantitative comparison of amplitude versus intensity interferometry for astronomy

Manuel Bojer*, Zixin Huang, Sebastian Karl, Stefan Richter, Pieter Kok, Joachim von Zanthier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)
19 Downloads (Pure)


Astronomical imaging can be broadly classified into two types. The first type is amplitude interferometry, which includes conventional optical telescopes and very large baseline interferometry (VLBI). The second type is intensity interferometry, which relies on Hanbury Brown and Twiss-type measurements. At optical frequencies, where direct phase measurements are impossible, amplitude interferometry has an effective numerical aperture that is limited by the distance from which photons can coherently interfere. Intensity interferometry, on the other hand, correlates only photon fluxes and can thus support much larger numerical apertures, but suffers from a reduced signal due to the low average photon number per mode in thermal light. It has hitherto not been clear which method is superior under realistic conditions. Here, we give a comparative analysis of the performance of amplitude and intensity interferometry, and we relate this to the fundamental resolution limit that can be achieved in any physical measurement. Using the benchmark problem of determining the separation between two distant thermal point sources, e.g., two adjacent stars, we give a short tutorial on optimal estimation theory and apply it to stellar interferometry. We find that for very small angular separations the large baseline achievable in intensity interferometry can more than compensate for the reduced signal strength. We also explore options for practical implementations of very large baseline intensity interferometry (VLBII).

Original languageEnglish
Article number043026
Pages (from-to)1-21
Number of pages21
JournalNew Journal of Physics
Issue number4
Publication statusPublished - 1 Apr 2022

Bibliographical note

Copyright © 2022 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • (quantum) Fisher information
  • imaging astronomical objects
  • quantum metrology


Dive into the research topics of 'A quantitative comparison of amplitude versus intensity interferometry for astronomy'. Together they form a unique fingerprint.

Cite this