Flip-flop Qubits for Scalable Quantum Computing Architectures

Flip-flop qubits (FFQ) are a promising qubit type based on a mixture of nuclear and bonded electron spin states of a ³¹P atom in a spin-free ²⁸Si substrate [1]. High-fidelity one-qubit operations can be obtained by exploiting electric dipole spin resonance and two-qubit ones are created by using electric dipole interaction [1,2]. The long-range dipole-dipole interaction between FFQs could relax the usually stringent fabrication requirements for spin-based qubits, particularly for the lateral positioning of gates/donors thus moving the specs from some tens of nm to few hundreds of nm range. The simultaneous application of gates, i.e. parallel gating, is a central ingredient for quantum computation, but gate parallelism is inevitably limited by unwanted inter-qubit interactions. The effects on gate fidelities of those unwanted mutual interactions, due to multi one-qubit and multi two-qubit gates executed in parallel, is simulated in different arrays embedded in a realistic noisy environment [3]. Such information helps to infer those for logical qubits defined by a quantum error correction code, also providing insights for system scaling-up in view of long-term silicon-based quantum computers. [1] Tosi et al., Nat. Comm. 2017, 8450. [2] Ferraro et al., arXiv:2104.14341v12021. [3] Rei et al., arXiv:2110.12982.