Paparazzo, who was able to "spy" and film the pairing of photons, received an award in this year\'s edition of the START Programme of the Foundation for Polish Science. Michał Jachura from the Faculty of Physics of the University of Warsaw describes unknown phenomena related to the quantum nature of light. Research can be useful, among other things, in quantum cryptography, encoding information in light.
The young researcher explores the Hong-Ou-Mandel effect, also known as two-photon interference. It consists in non-distinguishable photons "connecting" into pairs. Observation and recording of experiments is possible with the detection system developed by Warsaw physicists. Michał Jachura and Radosław Chrapkiewicz from the Faculty of Physics of the University of Warsaw, using the latest generation of cameras, were the first in the world to film single photons that match in pairs.
"The Hong-Ou-Mandel effect is observed by a pair of detectors, typically avalanche photodiodes, placed in the two output arms of a plate and an electronic module that registers only those cases where both detectors have observed a photon simultaneously" - explained Jachura.
Some two-photon and multi-photon interference applications, such as quantum imaging techniques, require, however, that in addition to the binary information that the photon was registered, the spatial coordinates of the point at which the detection occurred are also known.
"Detection of photon pairs and their interference is possible with a low noise sCMOS camera equipped with an external image amplifier. In our system, information about the location of detected photons pairs is read directly from the frames recorded by the camera. With the image amplifier, each of the recorded photons is visible in the frame as a bright flash with a very high signal to noise ratio" - added Jachura.
According to the scholarship winner, the future of today\'s quantum communication protocol depends on the efficiency of methods allowing to fully characterize the quantum states of individual photons. The spatial structure of photons described by wave functions is, next to the spectral structure, the most promising information carrier during free space communication, for example, during satellite communications. Unfortunately, the exact characterization of the single-photon wave function is still a very big experimental challenge.
Jachura and his co-authors proposed an innovative method of spatial reconstruction of the wave function of an unknown photon consisting in its interference, i.e., "connecting" into a pair with a photon of known properties. This method uses the bosonic properties of photons and can also be used to reconstruct the spatial phase of a total-spin single-atom spatial wave function.
Within the framework of the START Programme, the Foundation for Polish Science awards stipends to young scientists whose high quality of scientific achievements has been recognized as outstanding by the jury of the competition. This year, three laureates received distinctions. Their stipends will be increased to the amount of PLN 36,000 each The other winners are: Dr. Joanna Kułaga-Przymus from Nicolaus Copernicus University in Toruń and Mateusz Konczal from Adam Mickiewicz University in Poznań.
More about Michał Jachura\'s research (in Polish) in PAP - Science and Scholarship in Poland - here and here.
PAP - Science and Scholarship in Poland
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