Impact of valley phase and splitting on readout of silicon spin qubits

TL;DR

This paper explores how valley effects influence silicon spin qubit readout, demonstrating high-fidelity measurement possibilities and proposing a triple-dot latching protocol to enhance scalability and reliability.

Contribution

It analyzes valley phase and splitting impacts on spin qubit readout, proposing methods to optimize fidelity and a novel triple-dot latching protocol for improved measurement.

Findings

High-fidelity readout achievable across phase differences

Control of valley splitting can mitigate phase effects

Triple-dot latching protocol enhances measurement fidelity

Abstract

We investigate the effect of the valley degree of freedom on Pauli-spin blockade readout of spin qubits in silicon. The valley splitting energy sets the singlet-triplet splitting and thereby constrains the detuning range. The valley phase difference controls the relative strength of the intra- and inter-valley tunnel couplings, which, in the proposed Pauli-spin blockade readout scheme, couple singlets and polarized triplets, respectively. We find that high-fidelity readout is possible for a wide range of phase differences, while taking into account experimentally observed valley splittings and tunnel couplings. We also show that the control of the valley splitting together with the optimization of the readout detuning can compensate the effect of the valley phase difference. To increase the measurement fidelity and extend the relaxation time we propose a latching protocol that requires a triple quantum dot and exploits weak long-range tunnel coupling. These opportunities are promising for scaling spin qubit systems and improving qubit readout fidelity