Arne Laucht

Associate Professor, UNSW Sydney

Title: Global control of spin qubits in SiMOS quantum dots

Abstract:

Spin qubits are contenders for scalable quantum computation due to their long coherence times, but individual spin control by frequency-selective addressing using pulsed spin resonance creates severe technical challenges for scaling up to many qubits. Besides requiring high-frequency control signals and transmission lines for every qubit, this kind of control scheme also requires each spin to have a distinguishable frequency, imposing a maximum number of spins that can be individually driven before qubit crosstalk becomes unavoidable. In this talk, I will describe how a global control field can be used for addressing all qubits simultaneously. On the engineering side, this requires the generation of a macroscopic oscillating magnetic field, which we achieve with potassium tantalate dielectric resonators [1-3]. On the qubit control side, this requires a shift in paradigm from using the bare spin to using the dressed spin as the computational state [4,5]. In my talk, I will describe how we have realized this encoding for spin qubits in SiMOS quantum dots [6]. While the encoding facilitates local addressability of the qubits, the continuous global driving field extends the qubits’ coherence times by dynamically decoupling them from the effects of background magnetic field fluctuations.

[1] E. Vahapoglu, et al., “Single-electron spin resonance in a nanoelectronic device using a global field”, Science Advances 7, eabg9158 (2021).
[2] H. H. Vallabhapurapu, et al., “Fast Coherent Control of a Nitrogen-Vacancy-Center Spin Ensemble Using a KTaO3 Dielectric Resonator at Cryogenic Temperatures”, Phys. Rev. Appl. 16, 044051 (2021).
[3] E. Vahapoglu, et al., “Coherent control of electron spin qubits in silicon using a global field”, arXiv:2107.14622 (2021).
[4] A. Seedhouse, et al., “Quantum Computation Protocol for Dressed Spins in a Global Field”, Physical Review B 104, 235411 (2021).
[5] I. Hansen, et al., “Pulse engineering of a global field for robust and universal quantum computation”, Physical Review A 104, 062415 (2021).
[6] I. Hansen, et al., “Global qubit control via implementation of the SMART protocol in silicon”, arXiv:2108.00836 (2021).