Solid State Quantum Information

Quantum Dot Devices for Quantum Information Technology

speaker: Andrew Shields (Toshiba Research Europe Ltd)

abstract: We review progress on generating single photons and entangled pairs from semiconductor quantum dots. A semiconductor p-i-n junction containing a single quantum dot forms an LED for single photons. We demonstrate a design of single photon LED with high photon collection efficiency, in which an oxide annulus is used to restrict the drive current to a single dot and to also confine the optical mode to the vicinity of the dot. This electrically driven device displays a strong Purcell effect, allowing drive frequencies of 0.5GHz. Indistinguishable single photons may be generated through control of the electrical injection pulses to reduce the effect of dephasing in the quantum dot. Triggered entangled photon pairs may also be generated from the biexciton cascade of a single dot and demonstrate an entangled pair source with a fidelity to the expected Bell state of 91.4%. We show also that the phase of the generated entangled state may be controlled. This arises due to the coherent evolution of the intermediate entangled excitonphoton state of the biexciton cascade.

timetable:
Fri 5 Dec, 11:00 - 11:30, Sala Stemmi
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