A team including the Director at the Max Planck Institute of Quantum Optics, Professor Gerhard Rempe along with the Head of the Quantum Dynamics Division, has observed that light can be squeezed out of a single atom, thus delivering better dynamics.
The atom interacts strongly with light within a cavity to change the wave-like characteristics of the light field, thus lowering its phase or amplitude variations when compared to those permitted for traditional electromagnetic radiation. Researchers are observing squeezed light emitted from a single atom for the first time.
The atom in the cavity turns a laser beam into light which has less amplitude and more phase fluctuations than the shot-noise limit.
Photons in light waves have a certain “graininess,” due to which slight fluctuations of the wave’s phase and amplitude are caused. When interactions are created between photons the amplitude fluctuations can be squeezed below a shot-noise level at the cost of enhancing phase fluctuations and vice versa. Single atoms are capable of initiating such interactions with light by emitting photons. A single atom’s ability to emit squeezed light was discovered 30 years ago. However, the amount of light released is very low and all attempts to realize this phenomena have failed. Complex techniques have been developed over several years at MPQ to isolate, cool and handle single atoms, which resulted in the success of this observation.
A single rubidium atom is held within a cavity made using two reflective mirrors placed within one tenth of a millimetre. The presence of a weak laser light in this cavity enables the atom to react with a single photon several times to produce an artificial molecule with the light photons. As a result, two photons can penetrate the system simultaneously and get linked.
When a laser beam that matches the excitation frequency of the atom is used, the measurements show that the phase fluctuations are controlled. When researchers use a laser light source, which is resonant with the cavity, they witness a squeezing of the amplitude. The atom present in the cavity converts a laser beam, with low amplitude and greater phase variations when compared to the shot-noise, into light. The single atom’s capability to create coherent interactions of high-strength between propagating photons paves the way for photonic quantum logic using individual emitters.