Global control of spin qubits in SiMOS quantum dots*

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., Science Advances 7, eabg9158 (2021).

[2] H. H. Vallabhapurapu, et al., Phys. Rev. Appl. 16, 044051 (2021).

[3] E. Vahapoglu, et al., npj Quantum Information 8, 126 (2022).

[4] A. Seedhouse, et al., Physical Review B 104, 235411 (2021).

[5] I. Hansen, et al., Physical Review A 104, 062415 (2021).

[6] I. Hansen, et al., Applied Physics Reviews 9, 031409 (2022).