An ultra-high Q circuit optomechanical quantum memory with 2 milli-second lifetime*

Harnessing the high coherency of mechanical oscillators combined with microwave superconducting resonators makes circuit optomechanics an ideal platform to implement long-life quantum memories as a core quantum technology.

These systems are implemented by LC superconducting resonators with a mechanically compliant capacitor. The conventional design to realize circuit optomechanics enabled observation of several quantum phenomena such as ground-state cooling and entanglement of mechanical objects.  However, the low controllability in this design severely limits their scalability and properties, specifically the mechanical quality factor, which largely determines the thermal coherence time.

Here we introduce a novel design to make a flat high-stress trampoline resonator with mechanical quality factors up to 25 million. We demonstrated ground-state cooling of this resonator down to 0.2 quanta and measured the thermal decoherence rate of 60 quanta/second, corresponding to the lifetime of T1=2.3 ms in the ground state.