molecules of light

Dr. Ofer Furstenberg, who recently joined the faculty of the Department of Physics of Complex Systems at the Weizmann Institute of Science, recently reported on an experiment in which he, together with his research partners, succeeded in causing the formation of photon pairs, a kind of "molecules of light"

Particles of light, photons, do not tend to have too active a social life. A photon detector that measures the light that reaches it, for example, from a laser projector, reports individual light particles, arriving at random times that are independent of each other. But Dr. Ofer Furstenberg, who recently joined the faculty of the Department of Physics of Complex Systems at the Weizmann Institute of Science, reported not long ago on an experiment in which, together with his research partners, he succeeded in causing the formation of photon pairs, a kind of "molecules of light".

The photon pairs were, in fact, created when the laser beam passed through a thin, cold gas, which created a kind of attraction between the photons. That is, the unique properties of this medium meant that in order to reach the lowest possible energy state (to which every particle aspires), photons "should" get closer to each other, and form pairs.

In Dr. Furstenberg's laboratory, at the Weizmann Institute of Science, he plans to build two systems that will produce "molecules of light": one system will have the medium that creates the conditions for the photons to approach each other very cold, while the other system will operate at room temperature.

"Actually," says Dr. Furstenberg, "we launch two beams of laser beams. One beam is relatively powerful, and it creates a kind of tunnel in the gas of the medium. The medium in the tunnel is a billion times more transparent than the medium outside it, and we call this 'electrically induced transparency'. Next comes the weak laser beam, whose photons move slowly through the tunnel (about one millionth the speed of normal light). These photons hit the gas atoms, effectively jiggling their electrons. In this situation, the electrons of the gas atoms move very far from the nucleus of the atom. Atoms in this state are called 'Rydberg atoms', and they are thousands of times larger than atoms at rest."

When a pair of atoms in the medium gas are excited by a pair of photons of the weak laser beam, the oscillating electrons behave as a pair of antennas between which a force acts. These actual forces translate into an attraction between the photons, which causes the photon pairs to form.

This research may shed new light on the properties of light in the quantum world and on the particles of light, photons; For example, how does the effect of the forces between the photons differ from the effect of the actual forces between the particles of matter in nature. "It is possible that in this way we will discover new physical phenomena", adds Dr. Furstenberg. In the meantime, a system like the one he is building in his lab at the institute, capable of creating an "orderly train of photons", can help in efforts to measure gravitational waves through optical measurement.

personal

Dr. Ofer Furstenberg was born and raised in Rishon Lezion. During his military service in the "Talpiot" program, he studied for a bachelor's degree in physics at the Hebrew University of Jerusalem, and then went on to a master's and a master's degree at the Technion. He did his post-doctoral research at Harvard and MIT. In August 2014 he returned to Israel and joined the faculty of the Weizmann Institute of Science.