High kinetic inductance thin films for compact readout of CMOS-compatible spin qubits

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For quantum computers to fully demonstrate their advantage over classical approaches, the number of qubits available must significantly increase beyond that currently feasible using state of the art superconducting qubits. Spin qubits can be realised using silicon transistors fabricated in a way that is compatible with the CMOS processes used to manufacture chips found in modern technologies. Through the use of this mature silicon technology a qubit density of 1010 qubits/cm2 could be possible. However, the current readout circuitry reduces this value to 103 qubits/cm2 hindering the scalability that is the main benefit of a CMOS-compatible approach. To solve this issue, a high kinetic inductance (KI) material can be incorporated as the gate electrode to both confine electrons and act as the resonator for readout. This will reduce the size of the readout circuitry as a high inductance can be achieved in a smaller area due to the KI. To achieve this goal first involves investigating multiple high KI materials to determine their applicability. The material must demonstrate low loss and correspondingly high Q-factors for fabricated resonators as this determines the sensitivity to capacitance shifts used to readout the qubit state. Also of importance is their resilience to magnetic fields (_1T for singlet-triplet and _1.5T for other implementations) which are needed for manipulation of the spin qubits. Quantum dot devices that include the chosen high KI material as the gate electrode will then be designed, fabricated and tested. An understanding of these devices will allow the development of a nanowire with multiple gates to demonstrate the scalability of this approach with the fabrication of a 4-qubit unit cell.