Studying propagating acoustic waves at the single phonon level.

The project aims at studying propagating surface acoustic waves at the single phonon level. In a yet unoptimized experiment we have recently been able to show extraordinary sensitivity to mechanical waves. Using the extreme charge sensitivity of a Radio Frequency Single Electron transistor (RF-SET) and coupling charge to mechanical displacement via the piezoelectric properties of GaAs, we have demonstrated a displacement sensitivity of 30 am/vHz. We have used this to study propagating Surface Acoustic Saves (SAW) with a frequency of 1GHz on the surface of GaAs. The speed of the RF-SET has allowed us to follow SAW pulses in time as they pass the SET. Furthermore, pulses containing less than a single phonon can be detected by averaging many times. We aim at optimizing our set up and study propagation of phonons at the single phonon level. This is a long term project with the overall objective is to study quantum properties of single propagating phonons. Specifically we aim at: - Improving the sensitivity to allow single shot detection of a single phonon, i.e. without averaging. - Make beam splitters for phonons that will allow interference experiments. - Implement dual detectors that will allow correlation measurements. - Study phonons in high-Q SAW cavities. - Coupling the phonons to superconducting qubits.