Counting of phonons

Simon Gröblacher co-authors a Hanbury Brown and Twiss type experiment with phonons performed at Caltech, which was recently published in the renowned journal Nature. Pioneering photon counting experiments, such as the intensity interferometry performed by Hanbury Brown and Twiss to measure the angular width of visible stars, have played a critical role in our understanding of the full quantum nature of light. Over the last years the field of optomechanics, where a mechanical oscillator is coupled to light via the radiation-pressure force, has emerged as a leading candidate to observe complex quantum phenomena in truly macroscopic, massive systems.

Here we use an optical probe and single-photon detection to study the acoustic emission and absorption processes in a silicon nano-mechanical resonator, and perform a measurement similar to that used by Hanbury Brown and Twiss to measure correlations in the emitted phonons as the resonator undergoes a parametric instability formally equivalent to that of a laser. With straightforward improvements to this method, a variety of quantum state engineering tasks using mechanical resonators can be enabled, including the generation and heralding of single-phonon Fock states and the quantum entanglement of remote mechanical elements.

Figure: Finite element simulation of the nanobeam structure used to measure the phonon statistics of a mechanical oscillator using a Hanbury Brown and Twiss type experiment.

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