### QuMat seminar

## Decoherence of a silicon spin qubit under the action of a single charge fluctuator Speaker: Christophe Delerue – University of Lille, CNRS, Université Polytechnique Hauts-de-France |

Abstract:

Silicon is the semiconductor material in which most of today’s components and integrated circuits are manufactured by the microelectronics industry. It is therefore at the heart of the technologies that have revolutionized information processing and communications. Against this backdrop, many teams around the world are looking to exploit these microelectronic technologies to build future quantum computers and simulators. One strategy being widely pursued is to design qubits within silicon nanotransistors in which the intrinsic magnetic moment (spin) of a single electron (or hole) carries the quantum information. One of the many challenges posed by the development of these quantum technologies is to maintain the quantum coherence of the spin for as long as possible, while at the same time providing the means to manipulate this same spin efficiently and in a controlled manner. These two injunctions are in fact partly contradictory.

To illustrate this, we have carried out numerical modelling of a spin qubit based on a silicon nanowire transistor very close to what is technologically developed at CEA LETI in Grenoble [1]. This qubit is assumed to be perturbed by a single charge fluctuating randomly in its close vicinity. Despite its simplicity, this model is characterized by a very rich physics, which I will present in this talk. In particular, I will illustrate two distinct behaviors of the spin dynamics, depending on whether its Larmor frequency is larger or smaller than the characteristic frequency of the fluctuator. I will also show the limitations of the “two-level” model universally used to describe qubits.

[1] B. Shalak, C. Delerue, Y.M. Niquet, Phys. Rev. B 107, 125415 (2023).