Peter Daniel Johannsen

We consider hybrid systems consisting of a hole-doped semiconductor coupled to electronic states of finite-size superconductors, where the opposite sign of the masses in the two subsystems give rise to insulating gaps at subband anticrossings. Consequently, increasing the coupling strength to the superconductor can paradoxically suppress the proximity-induced superconductivity in the semiconductor by enhancing these insulating gaps. We demonstrate that the presence of such induced insulating gaps leads to a characteristic anomalous behavior of the critical supercurrent in Josephson junctions based on these hybrid structures. Our findings provide important insights for the design of robust quantum computing platforms utilizing hybrid superconductor-hole systems.

Arrays of superconducting qubits and cavities offer a promising route for realizing highly controllable artificial materials. However, many analog simulations of superconducting circuit hardware have focused on bosonic systems. Fermionic simulations, on the other hand, have largely relied on digital approaches that require non-local qubit couplings, which could limit their scalability. Here, we propose and study an alternative approach for analog fermionic quantum simulation based on arrays of coherently coupled mesoscopic Josephson junctions. These Josephson junction arrays implement an effective superlattice of Andreev bound state "atoms" that can trap individual fermionic quasiparticles and, due to their wavefunction overlap, mediate quasiparticle hoppings. By developing a Wannier function approach, we show that these Andreev bound state arrays form an all-superconducting and circuit QED-compatible platform for emulating lattice models of fermionic quasiparticles that are phase- and gate-programmable. Interestingly, we also find that the junction lattices can undergo a topological transition and host fermionic boundary modes that can be probed by conductance measurements. We hope our results will inspire the realization of artificial and possibly topological materials on Andreev bound state quantum simulators.