In 2016, scientists from the University of Warsaw created the first-ever hologram of a single light particle, adding new insights to the foundations of quantum mechanics.
Individual points of a picture in traditional photography merely register light intensity. The interference phenomenon also registers the phase of the light waves in traditional holography. A well-described, undisturbed reference wave is superimposed with another wave of the same wavelength reflected off a three-dimensional object when a hologram is generated. Interference occurs as a result of the phase variations between the two waves, resulting in a complicated pattern of lines.
The spatial structure of waveforms of light reflected from the object is then recreated by illuminating the hologram with a beam of the reference light, and so its 3D shape is recreated. Because individual photons have a continuous fluctuation, the Warsaw researchers took a novel approach to the problem: instead of employing conventional interference of electromagnetic waves, they attempted to register quantum interference, in which photon wave functions interact.
We performed a relatively simple experiment to measure and view something incredibly difficult to observe: the shape of wavefronts of a single photon.Radoslaw Chrapkiewicz
At its core, the experiment is simple: instead of looking at changing light intensity, they are measuring the changing probability of registering pairs of photons after the quantum interference.
The researchers obtained an interference image corresponding to the hologram of the unknown photon viewed from a single point in space by repeating the measurements numerous times.
Our experiment is one of the first allowing us to directly observe one of the fundamental parameters of photon’s wave function bringing us a step closer to understanding what the wave function really is.Michal Jachura
Hologram of a single photon, Radosław Chrapkiewicz, Michał Jachura, Konrad Banaszek & Wojciech Wasilewski
Published: July 2016