Operation of quantum dot spin qubits at elevated temperatures*

Quantum computers are expected to outperform conventional computers for a range of important problems, from molecular simulation to search algorithms, once they can be scaled up to large numbers of quantum bits (qubits), typically millions. Spin qubits in silicon MOS quantum dots are one of the big contenders for a scalable, solid state-based quantum computing platform. Here, the qubits are encoded as the spin states of individual electrons confined in electrostatically-gated quantum dots. The great potential of this system has been demonstrated through various experiments over the last few years, with coherence times of up to T₂=28 ms, single qubit control fidelities of 99.96%, and two-qubit control fidelities of 98%.

In my presentation, I will give an introduction to the SiMOS quantum dot spin qubits that we employ at UNSW Sydney. I will showcase some of the key experiments of the last years related to the experimental challenge of operating silicon spin qubits at temperatures above 1 K. High temperature operation is important for the integration of conventional CMOS control electronics with the qubit system, required for scaling to the millions of qubits that will be required for fault-tolerant quantum computing. In particular, I will describe the operation of a double-island single electron transistor (DISET) for charge readout. Using a DISET, we exploit the tunneling between two quantized states to achieve a highly improved insensitivity to temperature and a single-shot charge readout fidelity >99% at 8 K and a bandwidth of 100 kHz.