Mechanical resonators are emerging as an important new platform for quantum science and technologies. A large number of proposals for using them to store, process and transduce quantum information motivates the development of increasingly sophisticated techniques for controlling mechanical motion in the quantum regime. By interfacing mechanical resonators with superconducting circuits, circuit quantum acoustodynamics can make a variety of important tools available for manipulating and measuring motional quantum states. Here we demonstrate the direct measurements of phonon number distribution and parity of non-classical mechanical states. We do this by operating our system in the strong dispersive regime, where a superconducting qubit can be used to spectroscopically resolve the phonon Fock states. These measurements are some of the basic building blocks for constructing acoustic quantum memories and processors. Furthermore, our results open the door for performing even more complex quantum algorithms using mechanical systems, such as quantum error correction and multimode operations.
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We thank X. Cao and A. deMello for help with the flip-chip-bonding process and J.-C. Besse for help with the qubit fabrication. We thank B. Li for providing support with the QuTiP simulations. The fabrication of devices was performed at the FIRST cleanroom of ETH Zürich and the BRNC cleanroom of IBM Zürich. M.F. acknowledge The Branco Weiss Fellowship—Society in Science, administered by the ETH Zürich.
The authors declare no competing interests.
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von Lüpke, U., Yang, Y., Bild, M. et al. Parity measurement in the strong dispersive regime of circuit quantum acoustodynamics. Nat. Phys. (2022). https://doi.org/10.1038/s41567-022-01591-2