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Quantum diffusion of microcavity solitons


Coherently pumped (Kerr) solitons in an ideal optical microcavity are expected to undergo random quantum motion that determines fundamental performance limits in applications of the soliton microcombs1. Here this random walk and its impact on Kerr soliton timing jitter are studied experimentally. The quantum limit is discerned by measuring the relative position of counter-propagating solitons2. Their relative motion features weak interactions and also presents common-mode suppression of technical noise, which typically hides the quantum fluctuations. This is in contrast to co-propagating solitons, which are found to have relative timing jitter well below the quantum limit of a single soliton on account of strong correlation of their mutual motion. Good agreement is found between theory and experiment. The results establish the fundamental limits to timing jitter in soliton microcombs and provide new insights on multisoliton physics.

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Fig. 1: CP solitons and measurement of quantum-limited motion.
Fig. 2: Measured and theoretical jitter spectral density.
Fig. 3: Relative motion of CoP soliton pairs.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

The codes used for this study are available from the corresponding author upon reasonable request.


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This work is supported by the Air Force Office of Scientific Research (FA9550-18-1-0353) and the Kavli Institute of Nanoscience. C.B. acknowledges a postdoctoral fellowship from the Resnick Institute at Caltech. The work of A.B.M. was carried out at the JPL, Caltech, under a contract with the National Aeronautics and Space Administration.

Author information




C.B., K.Ş., A.B.M., F.X.K. and K.J.V. conceived the project. C.B. ran the experiments with assistance from B.S., Z.Y. and Q.-F.Y. M.-G.S., H.W. and L.W. prepared the samples. K.Ş., A.D. and F.X.K. built the BOC. The project was supervised by K.J.V.

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Correspondence to Kerry J. Vahala.

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The authors declare no competing interests.

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Peer review information Nature Physics thanks Giovanna Tissoni and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1 and 2 and Discussion.

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Bao, C., Suh, MG., Shen, B. et al. Quantum diffusion of microcavity solitons. Nat. Phys. 17, 462–466 (2021).

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