The Single-Photon Router

Understand

We have embedded an artificial atom, a superconducting "transmon" qubit, in an open transmission line and investigated the strong scattering of incident microwave photons ($\sim6$ GHz).

• When an input coherent state, with an average photon number $N\ll1$ is on resonance with the artificial atom, we observe extinction of up to 90% in the forward propagating field.
• We use two-tone spectroscopy to study scattering from excited states and we observe electromagnetically induced transparency (EIT).
• We then use EIT to make a single-photon router, where we can control to what output port an incoming signal is delivered.