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Single electron source generating individual photons for secure optical communications

Objective

The aim of this proposal is to develop a special optoelectronic nanocircuit that can produce either single photons or pulses of a fixed number of photons synchronized to a single electron generator. Operation of the nanocircuit is based on a high frequency surface acoustic wave that serves as a single electron pump for a lateral n-i-p junction. Compared with other existing approaches our single photon source will operate at higher temperatures, deliver photons at a much higher rate and can be implemented using well established processing techniques. A single photon source has for many years been a desirable device in the fields of quantum optics and quantum cryptography. Our suggested device can subsequently be used in developing practical secure optical communication channels with commercial significance. Such communication channels are likely to provide the ultimate solution to security and privacy issues of the information society. The aim of this proposal is to develop a special optoelectronic nanocircuit that can produce either single photons or pulses of a fixed number of photons synchronized to a single electron generator. Operation of the nanocircuit is based on a high frequency surface acoustic wave that serves as a single electron pump for a lateral n-i-p junction. Compared with other existing approaches our single photon source will operate at higher temperatures, deliver photons at a much higher rate and can be implemented using well established processing techniques. A single photon source has for many years been a desirable device in the fields of quantum optics and quantum cryptography. Our suggested device can subsequently be used in developing practical secure optical communication channels with commercial significance. Such communication channels are likely to provide the ultimate solution to security and privacy issues of the information society.

OBJECTIVES
The objective of the proposal is to develop a GaAs based nanoelectronic device, which generates separated single photons with high (up to GHz) repetition rate. The photons are formed by recombination of electrons and holes in a lateral n-i-p light emitting diode (LED). The best lateral n-i-p diode will be selected based on developments along independent routes. The single electron injection through a narrow one-dimensional electron channel will be driven by a surface acoustic wave (SAW), and this is the precondition of the single photon source. In order to separate the individual photons the recombination rate must be shorter than the repetition time of the electron injection. This is achieved by down-converting the electron injection rate by a GHz gate synchronously controlling an Y-branch directional electron waveguide. Luminescence from the p-region of the n-i-p diode caused by the SAW electron pumping and observation of single photon emission will be achieved.

DESCRIPTION OF WORK
The project will be in several parallel stages, since new development in MBE growth, a new lateral n-i-p diode, complicated e-beam processing, high frequency directivity of single electrons and a single photon detection scheme must be first developed. A continued theoretical support is necessary. The first stage of the work will be concerned with the preparation of a lateral n-i-p junction. We plan to use GaAs quantum well sandwiched between two AlGaAs layers in order to accommodate the electron channel. The n-i-p junction is created either by lateral variation in the modulation doping of the heterostructure or by creating a patterned back gate, which by suitable biasing may form the lateral n-i-p junction. A regrowth technique will be used for the patterned back gate. A split gate is needed to form a one-dimensional channel between the n- and p-regions. Submicron transducers and detectors for the surface acoustic wave are formed in the two regions, creating the movable periodic confinement along the channel, where each period traps a single (or precisely N) electron(s) on its way, often described in terms of moving quantum dots. A parallel approach of MBE growth with a simple back gate, without the complication of the n-i-p junction (a test wafer) will allow testing the acoustoelectric quantisation of the current and the high speed (GHz) synchronous switching of electrons between the two arms of a Y-branch directional switch. Fractional current quantisation may thus be achieved. The n-i-p light emitting diode will be tested before the complication of the single electron injection and the recombination rate and the effect on the luminescence from the p-region of an inserted MBE grown Bragg reflector will be investigated. The luminescence will be studied via an optical fibre to room temperature or directly at the low temperature. The last stage of the work will be the observation of true single photon emission from the SAWPHOTON source.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

KOEBENHAVNS UNIVERSITET
Address
Noerregade 10
1017 Copenhagen
Denmark

Participants (3)

SCUOLA NORMALE SUPERIORE
Italy
Address
Piazza Dei Cavalieri 7
56126 Pisa
THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
United Kingdom
Address
The Old Schools, Trinity Lane
CB2 1TN Cambridge
TOSHIBA RESEARCH EUROPE LIMITED
United Kingdom
Address
260 Cambridge Science Park, Milton Road
CB4 0WE Cambridge