«Quantum computers» are expected to solve problems beyond the reach of conventional computers. In a quantum computer, the information is not simply stored as a series of « 0 » or « 1 », but as a coherent superposition of all possible states. The preparation, coherent manipulation and measurement of such quantum states is extremely challenging. One promising option for making quantum bits is to divert silicon metal-oxide-semiconductor (MOS) transistors in order to trap one or a few electrons under control gates and manipulate their spin to store quantum information. The CEA Grenoble fabricates and characterizes such devices, and models their properties.
Model for two interacting spin qubits on a 2D array.
The qubits (red « crosses ») are etched in a silicon thin film. Calculated iso-density surfaces of the electron wave functions in these qubits are plotted in yellow and orange. Coulomb and tunnel interactions between the qubits give rise to an effective exchange coupling between their spins, which can be used to transfer coherently information and program conditional operations on these spins. The tunnel coupling between neighboring qubits is controlled by the potential on the metal gates (gray).
The objective of this PhD is to model the coherent manipulation of 1D and 2D arrays of spin qubits with a combination of analytical techniques and advanced numerical simulations on realistic systems. The aim is to optimize the structural design of these arrays [qubit geometry and arrangement, choice of materials (Si, Ge...)], as well as the control strategies (gates layout for improved addressability, signal shaping for enhanced fidelity, ...). The PhD candidate will have the opportunity to develop skills in the electronic structure of materials, in the dynamics of quantum systems in the presence of Coulomb interactions and noise (decoherence), and in computational physics. This PhD project will be carried out in close collaboration with the experimental physics teams working on spin qubits at CEA and CNRS (in the frame of the European ERC Synergy project quCube), as well as with the partners of the CEA in the European quantum flagship.
This PhD can be preceded by a Master 2 internship.