A high-fidelity heralded quantum squeezing gate


Squeezing operation is critical for continuous-variable quantum information, enabling encoding of information in phase space to a resolution otherwise forbidden by vacuum noise1. A universal squeezing gate that can squeeze arbitrary input states is particularly essential for continuous-variable quantum computation2,3. However, the fidelity of existing state-of-the-art implementations is ultimately limited due to their reliance on first synthesizing squeezed vacuum modes of unbounded energy4,5. Here, we circumvent this fundamental limitation by using a heralded squeezing gate. This allows improved gate fidelity without requiring more squeezed ancillary vacuum. For a specific target squeezing level for coherent states, we present measured fidelities higher than what would be possible using non-heralded schemes that utilize up to 15 dB (ref. 6) of best available ancilla squeezing. Our technique can be applied to non-Gaussian states and provides a promising pathway towards high-fidelity gate operations and fault-tolerant continuous-variable quantum computation.

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Fig. 1: Experimental layout of the heralded squeezing gate.
Fig. 2: Fidelity against success probability for various target squeezing values.
Fig. 3: Phase-space diagram for the squeezing gate.
Fig. 4: Improvement in fidelity over conventional techniques for a series of target squeezing values for states A–E.
Fig. 5: Fidelity as a function of filter strength and ancillary squeezing.

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.


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The research is supported by the Australian Research Council (ARC) under the Centre of Excellence for Quantum Computation and Communication Technology (CE110001027). K.L. is supported by the National Natural Science Foundation of China (grants 11674205 and 91536222). M.G. acknowledges funding from The National Research Foundation of Singapore (NRF Fellowship reference no. NRF-NRFF2016-02) and the Singapore Ministry of Education Tier 1 RG190/17. M.G. thanks the Institute of Advanced Study at NTU for funding the travel that catalysed this work. P.K.L. is an ARC Laureate Fellow.

Author information

S.M.A., J.Z., M.G., J.T. and P.K.L. conceived the experiment. S.M.A. and J.Z. developed the theoretical model. J.Z., K.L., H.J., S.M.A. and P.K.L. planned and performed the experiment. J.Z. and S.M.A. analysed the data. J.Z., S.M.A., H.J., J.T., M.G. and P.K.L. drafted the initial manuscript. All authors discussed the results and commented on the manuscript.

Correspondence to Ping Koy Lam.

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Supplementary Information

The Supplementary Information includes seven sections, Supplementary Figs. 1–7 and Supplementary Table 1.

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Zhao, J., Liu, K., Jeng, H. et al. A high-fidelity heralded quantum squeezing gate. Nat. Photonics (2020). https://doi.org/10.1038/s41566-020-0592-2

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