Figure 1

(a) Quantum circuit simulating the single Anderson or Kondo impurity model. The big square boxes are superconducting islands, connected by crossed squares which are Josephson junctions. A selected pair of islands is capacitively coupled and represents a magnetic impurity. The Josephson energy for tunneling between junctions are $J$ for the main lattice and $t$ around the impurity. (b) Two occupation states for the impurity representing a pseudospin state. (c) Energy levels of the impurity and a neighboring site. $n_{0\uparrow },n_{0\downarrow }$ and $N_r$ represent the number of pairs of the two islands in the impurity and the rest of the circuit. By external voltages, $-ϵ∕2$, and the capacitive coupling, $U\sim 1∕C$, it becomes favorable to have a single pair in the impurity.Reuse & Permissions

Figure 2

(a) Circuit for a two-channel single impurity Kondo system. Each half of the circuit is associated to a different channel. An extra junction with a negative sign, $t^{\prime }\simeq -J_K$, is a quantum interference element that prevents hopping between channels. (b) Circuit for a 1D Kondo lattice.Reuse & Permissions