Single-photon strong cooperativity in microwave magneto-mechanics

  1. D. Zöpfl,
  2. M.L. Juan,
  3. C. M. F. Schneider,
  4. and G. Kirchmair
The possibility to operate massive mechanical resonators in the quantum regime has become central in fundamental sciences, in particular to test the boundaries of quantum mechanics.
Optomechanics, where photons (e.g. optical, microwave) are coupled to mechanical motion, provide the tools to control mechanical motion near the fundamental quantum limits. Reaching single-photon strong coupling would allow to prepare the mechanical resonator in non-Gaussian quantum states. Yet, this regime remains challenging to achieve with massive resonators due to the small optomechanical couplings. Here we demonstrate a novel approach where a massive mechanical resonator is magnetically coupled to a microwave cavity. By improving the coupling by one order of magnitude over current microwave optomechanical systems, we achieve single-photon strong cooperativity, an important intermediate step to reach single-photon strong coupling. Such strong interaction allows for cooling the mechanical resonator with on average a single photon in the microwave cavity. Beyond tests for quantum foundations, our approach is also well suited as a quantum sensor or a microwave to optical transducer.

Bi-stability in a Mesoscopic Josephson Junction Array Resonator

  1. P.R. Muppalla,
  2. O. Gargiulo,
  3. S.I. Mirzaei,
  4. B. Prasanna Venkatesh,
  5. M.L. Juan,
  6. L. Grünhaupt,
  7. I.M. Pop,
  8. and G. Kirchmair
We present an experimental investigation of the switching dynamics of a stochastic bistability in a 1000 Josephson junctions array resonator with a resonance frequency in the GHz range.
As the device is in the regime where the anharmonicity is on the order of the linewidth, the bistability appears for a drive strength of only a few photons. We measure the dynamics of the bistability by continuously observing the jumps between the two metastable states, which occur with a rate ranging from a few Hz down to a few mHz. The switching rate strongly depends on the drive strength, pump strength and the temperature, following Kramer’s law. The interplay between nonlinearity and coupling, in this little explored regime, could provide a new resource for nondemolition measurements, single photon switches or even elements for autonomous quantum error correction.