In one minute

Lähteenmäki, Paraoanu, Hassel and Hakonen report a dynamical Casimir experiment in their four-page author manuscript, using a superconducting microwave cavity containing a Josephson metamaterial. An array of 250 SQUIDs in a 7 mm waveguide changes the cavity’s effective electrical length when its magnetic flux is modulated. At a cavity resonance of 5.4 GHz, pumping at 10.8 GHz generates correlated microwave photon pairs whose frequencies sum to the pump frequency. Measurements near 50 mK show two-mode correlations and a symmetric, double-peaked spectrum when the cavity is detuned, agreeing with the authors’ quantum model. The external modulation supplies the emitted energy; this is not an unpowered extraction device.

Dynamical Casimir effect in a Josephson metamaterial