Triplet blockade in a Josephson junction with a double quantum dot*

Topological superconductors are promising building blocks for future quantum computers, although their experimental realization remains a challenging task. I will present our theory results [1] on a Josephson junction with a double quantum dot. In the (1,1) charge sector of the serially coupled double quantum dot, I will illustrate a magnetically induced singlet-triplet ground-state transition via triplet blockade [2]: the Josephson current carried by the triplet ground state at high magnetic field is much suppressed compared to the current carried by the singlet ground state at low magnetic field. I will provide a simple interpretation for triplet blockade, using perturbation theory [3]. I will also present experimental data showing the triplet blockade predicted by the theory. The triplet blockade mechanism could provide a coupling mechanism between spin qubits, and superconducting qubits.

[1] D. Bouman et. al., https://arxiv.org/abs/2008.04375.
[2] S. Droste et al., Journal of Physics: Condensed Matter, 24 415301 (2012).
[3] B. I. Spivak and S. A. Kivelson, Physical Review B, 43 3740 (1991).