Modeling and Assessment of Qubits on Silicon – MAQSi

Quantum information technologies could lead to breakthroughs in computing/simulation and cryptography. France develops an original platform for quantum information, based on the "Silicon on Insulator" (SOI) technology. Yet many aspects of the physics of silicon quantum bits (qubits) remain poorly understood, which complicates the interpretation of the experiments and the optimization of the devices. The goal of the MAQSi project is to address modeling and simulation of silicon qubits in order to i) make significant progress in the understanding of the physics of these qubits, ii) sort the existing options, and make recommendations for the design of SOI qubits, iii) demonstrate ahead of the experimental work the relevance of SOI technologies for quantum information, and identify their strengths and weaknesses, in order to promote this platform. This project gathers two theoretical groups that have unique capabilities in France on the simulation of quantum silicon devices (INAC/MEM, CNRS/IEMN), with the experimental group that is leader in quantum CMOS measurements and coordinates European projects on the fabrication and measurements of SOI qubits (INAC/PHELIQS).

We will set-up tools for the microscopic and atomic scale simulation of silicon qubits and address the following challenges in MAQSi:
- Spin manipulation and readout: We intend to achieve fast, all electrical manipulation of electron and hole qubits relying as far as possible on the intrinsic spin-orbit coupling, For that purpose, we need to make progress in the understanding of spin-orbit coupling in silicon, and to optimize the design of the qubits.
- Decoherence and variability: We will characterize the disorders that limit the reproducibility (variability) and coherence of silicon qubits.
- Two qubit gates: We will investigate exchange coupling between qubits and assess the performances of two (or more) qubit gates.

The ambition of MAQSi is to solve these issues through a tight collaboration between experimental and modeling teams, These challenges can not, indeed, be efficiently addressed from an experimental only perspective due to the costs and time scales of device fabrication and characterization. As the quantum information technologies on silicon are developing very fast, it is extremely important to complement the experimental activity with state-of-the-art modeling able to give insights into the operation of silicon qubits and bring forward new ideas.