Research opens door to working quantum computer
1 min read
Research into technologies based on quantum effects that can be used to communicate and process information have resulted in a new development in which single photons can pass information between single atoms.
According to Max Planck, director at the Institute of Quantum Optics, a key element in the new system is electromagnetically induced transparency (EIT), an effect said to radically change the optical properties of an atomic medium by means of light.
EIT describes the effect that the interaction of an atomic medium with a weak laser field can be controlled and manipulated coherently with a second, strong laser field. This has been achieved by irradiating the medium with two laser beams as the action of a strong control laser causes the medium to become transparent for a weak probe laser. According to Planck, the properties derived from EIT allow the storing and retrieval of information between an atomic sample and light pulses, providing a powerful interface between photonic information and stationary atoms.
In an experiment, a single Rubidium atom was trapped inside a high finesse optical cavity in order to amplify the atom-light interaction so the atom and cavity formed a strongly coupled system. Then the transmission of laser light (the probe laser) incident on the cavity axis was measured. When there was no atom inside the cavity, the laser light was transmitted, but the presence of the atom caused the light to be reflected and the transmission dropped. With an additional control laser of very high intensity applied transverse to the cavity axis (see main picture), the single-atom EIT condition was achieved and maximum transmission was recovered.
The single atom effectively acts as a quantum optical transistor, coherently controlling the transmission of light through the cavity.
"Using EIT with a controlled number of atoms provides the possibility to manipulate many quantum properties of light fields transmitted by the cavity", said researcher, Martin Mücke. "Usually photons don't interact with each other. With this scheme we may be able to achieve a long sought goal: strong interaction between photons, mediated by a single atom. Such a set-up is a potential building block for a working quantum computer."
