  Electromagnetic fields carry momentum, which upon reflection on matter gives
rise to the radiation pressure of photons. The radiation pressure has recently
been utilized in cavity optomechanics for controlling mechanical motions of
macroscopic objects at the quantum limit. However, because of the weakness of
the interaction, attempts so far had to use a strong coherent drive to reach
the quantum limit Therefore, the single-photon quantum regime, where even the
presence of a totally off-resonant single photon alters the quantum state of
the mechanical mode significantly, is one of the next milestones in cavity
optomechanics. Here we demonstrate an artificial realization of the radiation
pressure of microwave photons acting on phonons in a surface acoustic wave
resonator. The order-of-magnitude enhancement of the interaction strength
originates in the well-tailored strong second-order nonlinearity of a
superconducting Josephson-junction circuit. The synthetic radiation pressure
interaction adds a key element to the quantum optomechanical toolbox and can be
applied to quantum information interfaces between electromagnetic and
mechanical degrees of freedom.

Quantum Physics