Inductively-Protected Andreev Spin Qubit 

Qubits use quantum superpositions to encode and process quantum information. However, unlike conventional bits, this makes them extremely susceptible to environmental fluctuations, leading to decoherence and relaxation. This has motivated the search for protected qubits that minimize sensitivity to these perturbations, extend coherence times, and improve the scalability of quantum processors.

Here, we present a new Inductively Protected-Andreev-spin qubit design based on a superconductor–semiconductor hybrid platform [1,2]. We extend the idea to an inductively shunted junction qubit with a well-defined quantum dot Josephson junction, which leads to a spin-split doublet ground state. The addition of an inductor (E_L​) provides the potential landscape to tune the system into a sweet spot, gaining phase-noise protection and enabling the separation of spin states of the quantum dot into two different minima (double-well potential), controlled by the ratio between the Josephson and inductive energies (E_J/E_L).