Spin blockade qubit in a superconducting junction

The authors interpret a recent pioneering experiment (Zgirski M. et al., Phys. Rev. Lett., 106 (2011) 257003) on quasiparticle manipulation in a superconducting break junction in terms of spin blockade drawing analogy with spin qubits. They propose a novel qubit design that exploits the spin state of two trapped quasiparticles. They detail the coherent control of all four spin states by resonant quantum manipulation and compute the corresponding Rabi frequencies. The read-out technique is based on the spin blockade that inhibits quasiparticle recombination in triplet states. The authors provide extensive microscopic estimations of the parameters of their model.