Quantum computation protocol for dressed spins in a global field

Abstract

Spin qubits are contenders for scalable quantum computation because of their long coherence times demonstrated in a variety of materials, but individual control by frequency-selective addressing using pulsed spin resonance creates severe technical challenges for scaling up to many qubits. This individual resonance control strategy requires each spin to have a distinguishable frequency, imposing a maximum number of spins that can be individually driven before qubit crosstalk becomes unavoidable. Here we describe a complete strategy for controlling a large array of spins in quantum dots dressed by an on-resonance global field, namely, a field that is constantly driving the spin qubits, to dynamically decouple from the effects of background magnetic field fluctuations. This approach---previously implemented for the control of single electron spins bound to electrons in impurities---is here harmonized with all other operations necessary for universal quantum computing with spins in quantum dots. We define the logical states as the dressed qubit states and discuss initialization and readout utilizing Pauli spin blockade, as well as single- and two-qubit control in the new basis. Finally, we critically analyze the limitations imposed by qubit variability and potential strategies to improve performance.