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Time-of-flight quantum tomography of an atom in an optical tweezer

Abstract

A single particle trapped in a harmonic potential can exhibit rich motional quantum states within its high-dimensional state space. Quantum characterization of motion is key, for example, in controlling or harnessing motion in trapped ion and atom systems or observing the quantum nature of the vibrational excitations of solid-state objects. Here we show that the direct measurement of position and momentum can be used for quantum tomography of motional states of a single trapped particle. We obtain the momentum of an atom in an optical tweezer via time-of-flight measurements, which, combined with trap harmonic evolution, grants us access to all quadrature distributions. Starting with non-classical motional states of a trapped neutral atom, we demonstrate the Wigner function negativity and coherence of non-stationary states. Our work will enable the characterization of the complex neutral atom motion that is of interest for quantum information and metrology, and for investigations of the quantum behaviour of massive levitated particles.

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Fig. 1: Tomography sequence and notation.
Fig. 2: Single-atom Fock-state preparation and imaging.
Fig. 3: Motional quantum state tomography via time-of-flight imaging and maximum likelihood estimation.

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Data availability

The data that support plots and other findings in this paper are available from the authors on reasonable request.

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Acknowledgements

We thank T. Thiele, S. Pampel and T.-W. Hsu for valuable insights and technical assistance, and K. Lehnert and A. Kaufman for input on the manuscript. We acknowledge funding from NSF grant PHYS 1734006, ONR grants N00014-17-1-2245 and N00014-21-1-2594, NSF QLCI award OMA 2016244, and the US Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator, and the Baur-SPIE Endowed Professor at JILA. W.J.D. acknowledges support from an NSF Graduate Fellowship.

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M.O.B., A.M.R., O.R.-I. and C.A.R. conceived and designed the experiments. M.O.B. and W.J.D. performed the experiments. M.O.B., S.R.M., W.J.D. and C.A.R. analysed the data. M.O.B., S.R.M., W.J.D., R.J.L.-S., A.M.R., O.R.-I. and C.A.R. contributed materials/analysis tools. M.O.B., S.R.M., W.J.D., R.J.L.-S., A.M.R., O.R.-I. and C.A.R. wrote the paper.

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Correspondence to M. O. Brown or C. A. Regal.

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Brown, M.O., Muleady, S.R., Dworschack, W.J. et al. Time-of-flight quantum tomography of an atom in an optical tweezer. Nat. Phys. 19, 569–573 (2023). https://doi.org/10.1038/s41567-022-01890-8

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