SAW driven source of polarised single photons (WP3-2)

Host: Cambridge University, Cambridge (UCAM)
Supervisor: C.J.B. Ford, Co-supervisor: C. Bäuerle (CNRS).

Cambridge

Antonio Rubino

I obtained my Bachelor degree in Physics from the University of Salerno in 2013 working on Superconducting Nanowire Single-Photon detectors (SNSPDs) based on high temperature superconductors.
In July 2015, I completed a master degree in Physics at the same University, with a thesis on quantum optics at single-photon level. For the latter, I performed most of the experimental activity at Single Quantum BV and at Delft University of Technology, with Erasmus funding. I studied the single-photon emission and two photon interference from a nanowire quantum dot, the improvement of SNSPDs based on NbTiN and cold filters for the blackbody radiation.
Currently, I am an ESR at Cambridge University, in the “Semiconductors physics group”, and my research is focused on polarized single-photon sources based on sound acoustic waves devices.

Objectives

In this project we will build on recent advances in which we transported single electrons back and forth between two quantum dots using SAWs.24 For a single-photon source (SPS), and then for electron-spin to photon-polarisation conversion, a SAW needs to transport a stream of single electrons into a region of holes. UCAM has developed devices in which both electrons and holes can be induced in an undoped GaAs/AlGaAs well by gates to form a lateral n-p junction. A SAW drags electrons across the junction. A ZnO layer will be deposited to enhance the SAW amplitude (comparing techniques with PDI/TWENTE).

Quantised SAW-driven current between electron and hole regions will be studied and UCAM’s new 300 mK scanning optical microscope will be used to detect light emission as each electron recombines with a hole in a high-density hole gas. Single photons should be emitted with a high repetition rate (ultimately e.g. 3GHz, though initially only 0.01% will be collected) and low jitter (<100ps). Devices for spin-polarising electrons, developed in WP3-3 at CNRS, will be adapted so that a SAW pulse transfers a spin-polarised electron to the hole gas, emitting a photon with circular polarisation matching the electron’s spin if it travels along the spin-quantisation axis. ESR will discuss results with theorists (WP3-4). To increase directionality and efficiency, later devices will use Bragg mirrors below and above the emitter (developed at PDI in WP3-1 and already used by TREL), keeping compatibility with induced devices. The strong similarities with WP1-1 (using Si at TWENTE) will be exploited.

Expected Results

ESR12-UCAM1 will fabricate SAW devices, learning the many fabrication techniques associated with optical and e-beam lithography and also characterisation methods (SEM, AFM, XRD). The ESR will learn RF electrical techniques and will make ultra-low current measurements of their devices to confirm quantised acousto-electric current, in cryostats at 4K and 300mK. The ESR will look for single photons using techniques learned at CHALMERS and PDI and photon-timing detectors and electronics loaned by TREL. They will incorporate spin-polarisation techniques learned at CNRS to design devices to convert electron spin to photon polarisation.   

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