Harvard University and MIT (Massachusetts Institute of Technology) scientists have identified a method to convert a laser beam in a controlled way into a stream of individual photons. The discovery is seen as an important step toward the development of quantum systems.
The novel method aims to create an electronic ‘gate’ through which only one photon could pass at a time. To achieve this, the team focused a laser beam through a dense cloud of rubidium atoms at 40 µK to produce an electromagnetically induced transparency (EIT) state, which makes the normally opaque cloud of atoms to be excited while letting photons pass through at slow speed. The team’s approach put the atoms in a Rydberg state, which does not allow a second photon to pass through if the first one is yet to emerge out of the cloud.
The system could form the basis of a single photon switch and also quantum logic gates where one photon could switch another photon’s direction of travel.