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Non-classical mechanical states guided in a phononic waveguide


The ability to create, manipulate and detect non-classical states of light has been key for many recent achievements in quantum physics and for developing quantum technologies. Achieving the same level of control over phonons, the quanta of vibrations, could have a similar impact, in particular on the fields of quantum sensing and quantum information processing. Here we present a crucial step towards this level of control and realize a single-mode waveguide for individual phonons in a suspended silicon microstructure. We use a cavity–waveguide architecture, where the cavity is used as a source and detector for the mechanical excitations while the waveguide has a free-standing end to reflect the phonons. This enables us to observe multiple round trips of phonons between the source and the reflector. The long mechanical lifetime of almost 100 μs demonstrates the possibility of nearly lossless transmission of single phonons over, in principle, tens of centimetres. Our experiment demonstrates full on-chip control over travelling single phonons strongly confined in the directions transverse to the propagation axis, potentially enabling a time-encoded multimode quantum memory at telecommunications wavelength and advanced quantum acoustics experiments.

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Fig. 1: Phononic waveguide design.
Fig. 2: Device characterization.
Fig. 3: Non-classical travelling phonons.
Fig. 4: Time-bin-encoded phonon states.

Data availability

Source data for the plots are available on Zenodo via Source data are provided with this paper.


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We thank E. Verhagen and R. Burgwal for valuable discussions and M. Forsch for experimental support. We further acknowledge assistance from the Kavli Nanolab Delft. This work is financially supported by the European Research Council (ERC CoG Q-ECHOS, 101001005), and by the Netherlands Organization for Scientific Research (NWO/OCW), as part of the Frontiers of Nanoscience programme, as well as through Vidi (680-47-541/994) and Vrij Programma (680-92-18-04) grants. R.S. also acknowledges funding from the European Union under a Marie Skłodowska-Curie COFUND fellowship.

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Authors and Affiliations



A.Z., R.S. and S.G. devised and planned the experiment. A.Z. simulated, designed and fabricated the sample. A.Z., R.S. and N.F. built the setup and performed the measurements. All authors analysed the data and wrote the manuscript. S.G. supervised the project.

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Correspondence to Simon Gröblacher.

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Nature Physics thanks Krishna Balram and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–10 and discussion.

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Zivari, A., Stockill, R., Fiaschi, N. et al. Non-classical mechanical states guided in a phononic waveguide. Nat. Phys. 18, 789–793 (2022).

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