Antonio Manesco | Searcharxiv

arXiv2026

Loopless multiterminal quantum circuits at odd parity

We theoretically investigate loopless multiterminal hybrid superconducting devices at odd fermion parity with time-reversal symmetry. We find that the energy-phase relationship has a double minimum corresponding to opposite windings of the superconducting phases. Spin-orbit coupling adds multi-axial spin splittings, which contrasts with two-terminal devices where spin dependence is uniaxial. Capacitive shunting localizes quantum circuit states in the wells and exponentially suppresses their splitting. For weak spin-orbit strength, the system has a four-dimensional spin-chirality low-energy subspace which can be universally controlled with electric fields only.

cond-mat.mes-hall↗

arXiv2024

Fermionic quantum computation with Cooper pair splitters

We propose a practical implementation of a universal quantum computer that uses local fermionic modes (LFM) rather than qubits. The device layout consists of quantum dots tunnel coupled by a hybrid superconducting island and a tunable capacitive coupling between the dots. We show that coherent control of Cooper pair splitting, elastic cotunneling, and Coulomb interactions allows us to implement the universal set of quantum gates defined by Bravyi and Kitaev. Due to the similarity with charge qubits, we expect charge noise to be the main source of decoherence. For this reason, we also consider an alternative design where the quantum dots have tunable coupling to the superconductor. In this second device design, we show that there is a sweetspot for which the local fermionic modes are charge neutral, making the device insensitive to charge noise effects. Finally, we compare both designs and their experimental limitations and suggest future efforts to overcome them.

cond-mat.mes-hall↗