Impact of valley phase and splitting on readout of silicon spin qubits
M. L.V. Tagliaferri (Kavli institute of nanoscience Delft, TU Delft - QCD/Veldhorst Lab, TU Delft - QuTech Advanced Research Centre)
P. L. Bavdaz (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, Student TU Delft)
W. Huang (University of New South Wales)
A. S. Dzurak (University of New South Wales)
D. Culcer (University of New South Wales)
M. Veldhorst (TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Veldhorst Lab, Kavli institute of nanoscience Delft)
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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 intervalley tunnel couplings, which, in the proposed Pauli-spin blockade readout scheme, couple singlets and polarized triplets, respectively. We find that high conversion fidelity 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.