The article (READ HERE) discusses the Hanbury Brown-Twiss (HBT) effect, which is crucial for intensity interferometry and quantum optics. Traditionally, the HBT effect is observed at only one frequency at a time, which limits its applications. The authors of the article present a new spectrometer capable of detecting the HBT effect across multiple frequencies simultaneously. Specifically, they observed the HBT effect at five different frequencies of the neon spectrum. This technology has significant potential for both classical and quantum applications.
"This is a completely new way of measuring distances between cosmic objects with very high precision, enabled by quantum-assisted techniques that we are developing in our group. It is a great achievement for our team because we have measured something that opens the way to phase-sensitive intensity interferometry for a broadband spectrum. This could potentially improve astrometric accuracy by orders of magnitude, which would have a significant impact on astrophysics and cosmology," explains Sergei Kulkov, one of the main authors of the article from the CAPADS laboratory at FNSPE.
The research was conducted in collaboration with prestigious institutions such as Brookhaven National Laboratory in the USA and EPFL University in Switzerland. This topic has already gained wider scientific recognition, and based on its success, the CAPADS laboratory has now received funding from the Czech Science Foundation (GA ČR) under the Junior Star project, led by Peter Švihra since January 2025.
"What we have measured is the first step towards successful intensity interferometry using time-precise detectors. Sergei played a key role, but overall, about a quarter of our CAPADS team was involved in the work," concludes the head of the scientific group, Peter Švihra.
An intensity interferometer is a type of device that uses the Hanbury Brown-Twiss effect. In astronomy, such an interferometer is commonly used to determine the apparent angular diameter of a radio source or star. If the distance to the object can be determined using parallax or another method, the physical diameter of the star can be inferred.
Modern advanced intensity interferometers are being developed on the island of La Palma in Spain, in Chile (based on the Cherenkov Telescope Array system), and at the Observatoire de la Côte d'Azur in France. In quantum optics, some devices that utilize correlation and anti-correlation effects in photon beams may be referred to as intensity interferometers, although this term is usually reserved for astronomical observatories.
For context: Intensity interferometry is capable of achieving a resolution on the order of milliarcseconds (mas), while quantum-assisted methods can achieve ~10–100 microarcseconds (μas) for bright stars.
More reading:
Inter-pixel cross-talk as background to two-photon interference effects in SPAD arrays - IOPscience