The Fermi problem with artificial atoms in circuit QED

Understand

We propose a feasible experimental test of a 1-D version of the Fermi problem using superconducting qubits.

• We give an explicit non-perturbative proof of strict causality in this model, showing that the probability of excitation of a two-level artificial atom with a dipolar coupling to a quantum field is completely independent of the other qubit until signals from it may arrive.
• We explain why this is in perfect agreement with the existence of nonlocal correlations and previous results which were used to claim apparent causality problems for Fermi's two-atom system.