New quantum research provides insight into how quantum light can be harnessed

A team of scientists from the Los Alamos National Laboratory propose that modulated quantum metasurfaces can control all properties of photonic qubits, a breakthrough that could impact the fields of quantum information, communications, detection and imaging, as well as harvesting energy and momentum. The results of their study were published yesterday in the journal Physical examination letters, published by the American Physical Society.

“People have been studying classical metasurfaces for a long time,” explains Diego Dalvit, who works in the Condensed Matter and Complex Systems group in the Theoretical Division of the Laboratory. “But we had this new idea, which was to modulate in time and space the optical properties of a quantum metasurface which allows us to manipulate, on demand, all the degrees of freedom of a single photon, which is the most basic unit of light. “

Metasurfaces are ultra-thin structures that can manipulate light in ways that are typically not seen in nature. In this case, the team developed a metasurface that looked like an array of turned crosses, which they can then manipulate with lasers or electrical pulses. They then proposed to shoot a single photon through the metasurface, where the photon splits into a superposition of multiple colors, paths, and rotational states that are all intertwined, generating what’s called quantum entanglement, which means that the single photon is able to inherit all of these different properties at once.

“When the metasurface is modulated with laser or electrical pulses, we can control the frequency of the refracted single photon, change its trajectory angle, the direction of its electric field, as well as its torsion,” says Abul Azad of the Center for Integrated Nanotechnologies in the Physics of Materials and Applications Division of the Laboratory.

By manipulating these properties, this technology could be used to encode information in photons traveling in a quantum network, from banks, quantum computers, and between Earth and satellites. Encoding of photons is particularly desirable in the field of cryptography because “spies” are unable to visualize a photon without altering its fundamental physics, which, if done, would then alert the sender and receiver that the information has been compromised.

Researchers are also working on how to extract photons from a vacuum by modulating the quantum metasurface.

“The quantum vacuum is not empty but full of ephemeral virtual photons. With the modulated quantum metasurface, we are able to efficiently extract and convert virtual photons into pairs of real photons,” explains Wilton Kort-Kamp, who works in the theoretical division of the Condensed Matter and Complex Systems Group laboratory.

Harnessing the photons that exist in a vacuum and shooting them in one direction should create propulsion in the opposite direction. Likewise, the stirring of the vacuum should create a rotational motion from the twisted photons. Structured quantum light could then one day be used to generate mechanical thrust, using only tiny amounts of energy to drive the metasurface.