Hole spin qubits in Si and Ge quantum dots are promising platforms for quantum computing because of their large spin-orbit interactions, permitting efficient and ultrafast all-electric qubit control. I will present schemes to optimize the strength of these interactions in different architecture and show how to harness them to enhance the coupling of confined spins to microwave photons. Strikingly, in hole spin qubits this large spin-photon coupling can also tuned to be longitudinal, enabling high fidelity and fast two qubit gates with exact protocols that could work at high temperatures. On the other hand, spin-orbit interactions also couple the qubit to charge noise, reducing its coherence time. I will discuss ways to engineer and tune the spin-orbit interaction to enable sweet spots where the charge noise can be completely removed. Remarkably, in Si FinFETs, also the noise caused by hyperfine interactions with nuclear spins -another leading source of decoherence in spin qubits- can be suppressed at these sweet spots, greatly enhancing the coherence of these qubits, and reducing the need for expensive isotopically purified materials.
University of Basel
Quantum computation with hole spin qubits in Si and Ge quantum dots