Coherent optical interface for spin qubits in gate defined quantum dots

Qubit with optical interface Pascal Cerfontaine

Quantum networking would enable the connection of quantum processing nodes to increase computing power, long distance intrinsically secure communication, and the sharing of quantum resources over wide networks. Fully realizing these prospects requires local nodes with many coupled qubits connected by photonic links. Currently, qubits with good prospects for scaling to large numbers provide no optical interface, while optically addressable systems appear difficult to scale. This project aims to establish the fundamentals for quantum networks consisting of potentially scalable semiconductor spin qubits in gated GaAs quantum dots. These electrically controlled qubits have been proven viable for quantum computing, but so far have not been interfaced coherently with photons.

To achieve the latter, we plan to use a novel approach to create bound exciton states in a semiconductor structure that also hosts quantum dot qubits. These hybrid devices will make results from semiconductor quantum optics and self-assembled quantum dots applicable to gate-defined quantum dots.

Building on the capability to optically address our qubits, we plan to implement a protocol to transfer their quantum state to a photon. Eventually, we aim to integrate a photon interface into two-qubit devices to entangle separate semiconductor qubits via a photonic link, thus demonstrating a a minimal quantum network.

An important first step for this project will be the construction of a confocal microscope in a dilution refrigerator that is suitable to operate our qubits.