The Department of Physics colloquia includes internationally prominent guest speakers. They take place on Fridays during the semester and are open to anyone from the university, with students encouraged to attend.
Professor Ruth Oulton
Nanolightbulbs: a bright future for quantum technology
The “single photon source” is more than just a very “dim” source of light. The ability to trigger, precisely one, and only one, photon, would lead to a breakthrough in the field of photonic quantum technologies. By encoding information into the polarization of the photon, it can be made to carry information about its source. In this case, the source is a nanosized region of a semiconductor known as a quantum dot. By carefully controlling how the quantum dot interacts with light, an electron in the quantum dot can transfer information about its spin to the photon polarization.
This link between the spin and the photon polarization is known as “quantum entanglement”. What this means is that, when prepared in the correct way, the photon polarization and the spin are both in an undetermined state, but linked, such that when the photon polarization is measured, this may change the spin of the electron. This has important implications in building quantum networks: one may build up quantum dot spin “nodes” and link them into a network via the photonic states which travel from one node to another. This concept, while simple, is powerful: the network developed inherits unique properties from entanglement. The photons act to entangle the spin nodes together: this means that an operation on one spin affects many at the same time. These networks will use semiconductor and photonic technology to create a new way of processing information.