Manipulating single fermions with light in cQED architectures

ongoing

FERMIcQED aims at interfacing novel quantum materials with microwave light at the level of the single photon and fermion. To achieve this ambitious goal, I plan to use low-dimensional quantum conductors – such as carbon nanotubes or semiconducting nanowires – combined with state-of-the-art architectures and techniques of circuit Quantum Electrodynamics. The idea consists in isolating an individual fermionic degree of freedom within a hybrid Josephson junction – a quantum dot connected to two superconductors. Due to the superconducting proximity effect, entangled electron-hole states – called the Andreev bound states – form in the quantum dot and depend on the superconducting phase difference. By enclosing the hybrid Josephson junction inside a superconducting photonic cavity, one can couple these fermionic states to microwave light and probe their quantum properties in a well-controlled environment. Specifically, FERMIcQED will tackle three key experiments. First, we will detect the spin degree of freedom of the Andreev bound states and manipulate it coherently as a superconducting spin qubit. We will demonstrate strong coupling with cavity photons, which will enable quantum logic operations and long-range qubit interactions. Second, we will operate the hybrid Josephson junction in the topological regime in order to observe and manipulate Majorana fermions, thus implementing a topological qubit. At last, we will probe the joint entangled dynamics of bosonic and fermionic modes that coexist in hybrid Josephson junctions and simulate the spin-boson problem.