Observation of a discrete time crystal (original) (raw)

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Acknowledgements

We acknowledge discussions with M. Zaletel and D. Stamper-Kurn. This work was supported by the ARO Atomic and Molecular Physics Program, the AFOSR MURI on Quantum Measurement and Verification, the IARPA LogiQ program, the IC Postdoctoral Research Fellowship Program, the NSF Physics Frontier Center at JQI (and the PFC Seed Grant), and the Miller Institute for Basic Research in Science. A.V. was supported by the AFOSR MURI grant FA9550- 14-1-0035 and the Simons Investigator Program. N.Y.Y. acknowledges support from the LDRD Program of LBNL under US DOE Contract No. DE-AC02-05CH11231.

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Authors and Affiliations

  1. University of Maryland Department of Physics and National Institute of Standards and Technology, Joint Quantum Institute, College Park, Maryland, 20742, USA
    J. Zhang, P. W. Hess, A. Kyprianidis, P. Becker, A. Lee, J. Smith, G. Pagano & C. Monroe
  2. Department of Physics, University of California Berkeley, Berkeley, 94720, California, USA
    I.-D. Potirniche, A. Vishwanath & N. Y. Yao
  3. Department of Physics, University of Texas at Austin, Austin, 78712, Texas, USA
    A. C. Potter
  4. Department of Physics, Harvard University, Cambridge, 02138, Massachusetts, USA
    A. Vishwanath
  5. IonQ, Inc., College Park, Maryland, 20742, USA
    C. Monroe

Authors

  1. J. Zhang
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  2. P. W. Hess
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  3. A. Kyprianidis
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  4. P. Becker
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  5. A. Lee
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  6. J. Smith
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  7. G. Pagano
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  8. I.-D. Potirniche
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  9. A. C. Potter
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  10. A. Vishwanath
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  11. N. Y. Yao
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  12. C. Monroe
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Contributions

J.Z., P.W.H., A.K., P.B., A.L., J.S., G.P. and C.M. all contributed to experimental design, construction, data collection and analysis. I.-D.P., A.C.P., A.V. and N.Y.Y. all contributed to the theory for the experiment. All work was performed under the guidance of N.Y.Y. and C.M. All authors contributed to this manuscript.

Corresponding author

Correspondence toJ. Zhang.

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Competing interests

C.M. is a founding scientist of ionQ, Inc.

Additional information

Reviewer Information Nature thanks H. Haeffner and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 Experimental pulse sequence.

Bottom left, we initialize the spins via optical pumping plus a spin rotation, and then start the Floquet evolution. Each period includes the three parts of the Hamiltonian as described in the main text and Methods (top left), and is repeated for 100 times. We then perform an analysis rotation to the desired direction on the Bloch sphere, and then perform spin state detection (bottom right). Inset at top right, all pulses in the Floquet evolution are shaped with a ‘Tukey’ window. See text for detailed explanations.

Extended Data Figure 2 Build-up of a DTC.

From a to b to c, we fix the disorder instance (that is, a single sample of the random disorder realizations) and the perturbation ε, while gradually increasing the interactions (2_J_0_t_2) for different experimental runs. The temporal oscillations are synchronized with increasing interactions, and the Fourier subharmonic peak is enhanced. The top panel shows the time-traces of the individual spin magnetizations, and the bottom panel shows the Fourier spectrum.

Extended Data Figure 3 Comparing the ions’ dynamics with and without disorder.

a, Without disorder (_W_0_t_3 set to 0), the spin–spin interactions suppress the beatnote imposed by the external perturbation ε. Left, experimental data; right, exact numerics calculated under Floquet time-evolution. b, With disorder (_W_0_t_3 = π), the time crystal is more stable. Left, experimental result for a single disorder instance; right, numerical simulations. The top panels show the individual spin magnetizations as a function of time, and the bottom panels shows the Fourier transforms to the frequency domain.

Extended Data Figure 4 Finite size scaling.

Shown are subharmonic central peak heights as a function of the perturbation, for different numbers of ions, N = 10, 12, and 14. We observe a sharpening, that is, that the curvature of the slope is increasing, as the chain size grows, consistent with expectations. Each curve contains one disorder realization, which is a single sample of random instance with _W_0_t_3 = π, but the data are averaged over all the ions (yielding the error bars shown). Inset, phenomenological scaling collapse of the three curves10, with the following parameters: ε c = 0.041, v = 0.33, β = 1.9, which are critical exponents following the analysis in ref. 10. The extracted value of ε c is consistent with the interaction strength, which is fixed at 2_J_0_t_2 = 0.048 throughout this dataset.

Extended Data Figure 5 Different initial states.

Starting with the left half of the chain initialized in the opposite direction, we observe that the time crystal is still persistent in the presence of perturbations. Top left, time-dependent magnetizations for ions in the first half of the chain. Bottom left, magnetizations for the second half. Notice that the spins on the two halves oscillate with opposite phases throughout, until the end of the evolution. Right, average peak height as a function of perturbation. Inset, FFT spectrum for 2% perturbation. 2_J_0_t_2 was fixed at 0.048 throughout this dataset.

Extended Data Figure 6 A random sampling from numerical evolutions.

Shown are averages of 10 disorder instances from numerical evolution under H for 2_J_0_t_2 = 0.072. Left, an example random numerical dataset (points) and the fit to equation (3) in Methods (dashed line). Right, the normalized probability distribution (PDF) of peak fit centres ε p is shown in yellow, and a normal distribution is overlaid in red. The normal distribution is fitted using only the mean and standard deviation of the sample, showing excellent agreement with Gaussian statistics. For this value of _J_0 the mean and the standard deviation σε p = 0.006.

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Zhang, J., Hess, P., Kyprianidis, A. et al. Observation of a discrete time crystal.Nature 543, 217–220 (2017). https://doi.org/10.1038/nature21413

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