In-situ frequency tuning of photons stored in a high Q microwave cavity

Understand

Photons are fundamental excitations of the electromagnetic field and can be captured in cavities.

• For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific "colour".
• The cavity also has a typical lifetime tau, which results in a finite linewidth delta f}.
• If the size of the cavity is changed fast compared to tau, and so that the frequency change Delta f >> delta f, then it is possible to change the "colour" of the captured photons.