Summary

"Quantum computers" may soon be able to solve problems beyond the reach of conventional computers. Such computers no longer manipulate electrons as particles, but as waves that maintain phase relationships and can interfere. The preparation, coherent manipulation and "reading" of quantum states is extremely challenging. One promising option for making quantum bits (qubits) is to store electrons in silicon quantum dots and manipulate their spin. The CEA-Grenoble fabricates and characterizes such devices, and develops appropriate tools for their modeling. The objective of this Master training is to contribute to the design of 2D arrays of qubits on silicon through numerical simulations at the nanoscale. The impact of the layout of these arrays, of their dimensions, and of the choice of materials on the physics of the qubits will, in particular, be investigated. The outcome of these simulations will be used as guidelines for the design and integration of 2D arrays of qubits at CEA/LETI. This Master training will, therefore, be tightly connected to the ongoing experimental activity on silicon qubits at CEA and CNRS in Grenoble.

Full description of the subject

The electronic properties of the arrays of qubits will be computed with the “TB_Sim” code. This code is a platform for the modeling of the structural and electronic properties of semiconductor nanostructures. It has been used in the past few years on a variety of problems dealing with spin qubits on silicon. The goal of this master training is to get a better understanding of the properties of the 2D arrays of silicon qubits proposed in the ERC Synergy project “quCube” lead by Maud Vinet (CEA/LETI), Silvano de Franceschi (CEA/IRIG) and Tristan Meunier (CNRS/Néel). These arrays feature two layers of quantum dots one on top of each other, the top one being used to store quantum information, and the bottom one for readout purposes. The Coulomb and tunnel interactions between the dots in the top layer (exchange coupling) and between the top and bottom layer are extremely complex. The choice of layout, dimensions and materials in these arrays is expected to play a critical role that calls for a careful investigation. The numerical simulations will help uncover the main trends and build models for the physics of these arrays. They will be used to set guidelines for the design and integration of these arrays at CEA/LETI.

Requested skills 

Quantum physics/Taste for numerical modeling.