Correlations between entangled photons are a key ingredient for testing fundamental aspects of quantum mechanics and an invaluable resource for quantum technologies. However, scattering from a dynamic medium typically scrambles and averages out such correlations. Here we show that multiply scattered entangled photons reflected from a dynamic complex medium remain partially correlated. In experiments and full-wave simulations we observe enhanced correlations, within an angular range determined by the transport mean free path, which prevail over disorder averaging. Theoretical analysis reveals that this enhancement arises from the interference between scattering trajectories, in which the photons leave the sample and are then virtually reinjected back into it. These paths are the quantum counterpart of the paths that lead to the coherent backscattering of classical light. This work points to opportunities for entanglement transport despite dynamic multiple scattering in complex systems.
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Source data are provided with this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
Simulations performed in this work use the augmented partial factorization method implemented in software MESTI, available at https://github.com/complexphoton/MESTI.m.
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Funding: Zuckerman STEM Leadership Program, the Israel Science Foundation (grant no. 2497/21), National Science Foundation (ECCS-2146021), LABEX WIFI (Laboratory of Excellence within the French Program ‘Investments for the Future’) under references ANR-10-LABX-24 and ANR-10-IDEX-0001-02 PSL*.
The authors declare no competing interests.
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Safadi, M., Lib, O., Lin, HC. et al. Coherent backscattering of entangled photon pairs. Nat. Phys. 19, 562–568 (2023). https://doi.org/10.1038/s41567-022-01895-3