Across the globe, physicists in academia and industry alike are competing to be the first to build a scalable universal quantum computer. Amongst the multitudes of quantum computing architectures, solid-state quantum processors based on spins in silicon are emerging as a strong contender. Silicon is an ideal material to host spin qubits: it supports long coherence times [1], has excellent prospects for scaling, and is ubiquitous in the semiconductor industry. While semiconductor spin qubits were proposed over two decades ago [2], it is only within the past few years that we have learned how to fabricate and control multi-qubit devices in silicon.
In this seminar, I will describe our state-of-the-art four-qubit Si/SiGe quantum dot device [3] and explain how we have overcome major barriers to realizing large-scale quantum computing in silicon. First, I will discuss charge control and spin-state readout in the device. Then, I will describe the use of an on-chip micromagnet to mediate electrically driven spin resonance [4-5]. Using this technique, we achieve site-selective spin control with fidelities exceeding 99.9%. I will outline the operation of our three primitive two-qubit gates: the decoupled-CZ gate [4], the resonant CNOT gate [5], and the resonant SWAP gate [6]. Finally, I will discuss how these advances enable the development of large-scale quantum processors capable of complex quantum information processing.
