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Charge control in semiconductor quantum-dot arrays
and prospects for large-scale integration

Amphi A: 30 people max
Visio link: soon

The second quantum revolution is underway with the promise of harnessing the full potential of quantum mechanics to develop new technologies. Among these innovations, the field of quantum information theory proposes a new paradigm to perform computation, outside of the classical computing framework based on 0/1 bit of information. Quantum computing offers a way to solve physics and computational problems that cannot be solved in a reasonable time by classical computers by introducing quantum-bits (qubits) and quantum logic gates. However, quantum computers are prone to errors, requiring them to encode information from a single logical into multiple physical qubits. Thus, a universal quantum computer outperforming today’s supercomputers involves the control of millions of qubits, far from the dozens of qubits in current systems. In this context, spin qubits in quantum-dot (QD) arrays are a good candidate thanks to their compatibility with standard semiconductor manufacturing.

In this thesis, we focus on the charge control of electrons inside arrays of quantum-dots. On the one hand, we demonstrate remote charge sensing in a CMOS nanowire, using an embedded single-lead quantum-dot (SLQD) electrometer. A unique electrode operates each QD, and the device is fabricated on a silicon-on-insulator 300-mm industry-standard fabrication line. We develop different detection schemes to compensate for the device’s strong capacitive couplings due to its dense packing. Consequently, we control the different double quantum-dots in a 2×2 QD array and probe the Coulomb disorder inside the structure.

On the other hand, we demonstrate a scalable QD array formed by shared control gates with row/column addressing in a GaAs/AlGaAs heterostructure. Like classical integrated circuits, large-scale quantum-dot arrays must rely on shared controls to reduce the number of interconnects to √N, with N the number of QDs. Here, we show the charge control of electrons in a scalable 2×2 QD array isolated from the reservoirs. We characterize the array using the constant interaction model and assess its scalability. To conclude, these two experiments path the way towards charge controls in large-scale semiconductor QD arrays.

Thesis Director: Tristan MEUNIER