Photonic Router Opens Way To Quantum Computing

Photonic Router Opens Way To Quantum Computing

17 July 2014

Researchers at the Weizmann Institute of Science in Rehovot, Israel, have developed a device able to either transmit or redirect incoming photons - practically acting as a photonic router, reports, quoting research published in the journal Science.

The device is based on a single atom connected to a fiber-coupled, chip-based microresonator. A photon originating from the right would be allowed to continue moving left, if the atom is in one state. But if it is hit by a photon that originates from the left, the atom will alter its state and reflect the photon back left.

Then, when the atom is in its reversed state, photons coming from the left would be allowed to move right. In that state, photons coming from the right will be the ones being reflected - flipping the atom back to its original state. The two states the atom toggles between are of high reflection (R ~ 65%) and of high transmission (T ~ 90%).

The atom essentially functions as a transistor for the photons, explains the Institute's quantum optics group head Barak Dayan, likening the way it interacts with photons to the way electronic transistors switch electric currents. Photons, however, have weak interaction with other particles and don't interact with each other at all, which would make them suitable for routing between quantum systems.

This way scientists can overcome one of the biggest challenges before developing quantum computers, even though in Dayan's words such devices are still a long way off. The Institute's future experiments will focus on devices that function only on photons, like quantum memory or logic gates, he says.