Figure 1

Detector design. Sketch showing a one-dimensional waveguide (gray bars) coupled to a set of three-level absorbers (squares) in arbitrary positions. The microwave field (dashed line) excites coherently the state $|0⟩$ to the upper state $|1⟩$, which decays onto a long-lived stable state. An analogous setup uses current-biased Josephson junctions, in which a washboard potential confines two metastable states that can decay into a continuum of current states.Reuse & Permissions

Figure 2

Detection efficiency when absorbers are on resonance (real $\gamma$). (Top) Absorption probability vs effective decay rate $\gamma =\Gamma v_g/V^2$ in dimensionless units for a setup with $N=1$, 2, 4, and 8 qubits either in cluster (dashed) or array (solid) regime. The error bars account for random deviations in the individual absorber properties, ${\gamma }_i$, of up to 40%. When absorbers are close together, the efficiency is limited to 50%, while in the other case there is no upper limit. (Bottom) Detection efficiency vs separation $d$ in a periodically distributed array of absorbers.Reuse & Permissions

Figure 3

(a) Maximal achievable single-photon detection efficiency as a function of the number of qubits along the microwave guide. (b) Optimal working parameters vs number of qubits.Reuse & Permissions