Abstract: An optical data retrieval system configured to retrieve data from a data storage medium, including: a source of n path-entangled photons, where n is an integer of at least 2; a detector system configured to determine if n photons have been received; and a mechanism to direct photons from the source to the data storage medium and to the detector system.

Abstract: An optical system including: a photon source; first directing elements configured to direct photons to follow a first path through the optical system; second directing elements configured to direct photons to follow a second path through the optical system, wherein the second path is the reverse of the first path, photons travelling through the first path having a different polarization to those travelling through the second path; and a mechanism varying the relative phase shift between photons following the first path and photons following the second path.

Abstract: A photon source comprising a quantum dot comprising a confined conduction band energy level capable of being populated with at least one carrier and a confined valence band energy level capable of being populated by at least one carrier is provided, the source further comprises supply means for intermittently supplying at least one carrier to the energy levels to create an exciton in the quantum dot, wherein the supply means are configured to regulate the supply of carriers such that as the exciton decays either a single photon or a plurality of single photons each having different distinct energies are emitted during a predetermined time interval. The source is configured to be able to enhance the production of a desired type of exciton and can also be configured to exploit the use of higher order excitons such as biexcitons.

Abstract: A photon source for emitting entangled photons, the source comprising: at least one quantum dot having a degenerate exciton level; and exciton creation means to create a biexciton or higher order exciton within the at least one quantum dot.

Abstract: A photon source includes a photon source body including quantum dots, a non-insulating layer overlying and in contact with the quantum dots, and an electrical contact that allows electrically activated emission of radiation from at least one of the quantum dots. An active region is defined within the photon source body such that emission is only collected from a dot or a limited number of dots within the active region.

Abstract: A photon source for emitting entangled photons, the source comprising:

Abstract: A photon source comprising a photon source body, said photon source body comprising a plurality of quantum dots and at least one electrical contact, configured to allow electrically activated emission of radiation from at least one of the quantum dots, the photon source further comprising means for defining an active region within said photon source body such that emission is only collected from a dot or a limited number of dots within said active area.

Abstract: A photon source comprising a quantum dot comprising a confined conduction band energy level capable of being populated with at least one carrier and a confined valence band energy level capable of being populated by at least one carrier is provided, the source further comprises supply means for intermittently supplying at least one carrier to the energy levels to create an exciton in the quantum dot, wherein the supply means are configured to regulate the supply of carriers such that as the exciton decays either a single photon or a plurality of single photons each having different distinct energies are emitted during a predetermined time interval. The source is configured to be able to enhance the production of a desired type of exciton and can also be configured to exploit the use of higher order excitons such as biexcitons.