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Quantum Computing, Communication, and Simulation

Quantum sensing and ghost imaging

L. Davidovich, R. L. de Matos Filho

Published Mar 8, 2023• 1 citation
Publisher

Abstract

We show that the strategy of ghost imaging can be successfully adapted to the estimation of parameters of open systems. Two entangled qubits, so that only one of them interacts with a depolarizing sample, may lead to precision in the estimation of the depolarizing parameter better than the one corresponding to sending the pair, entangled or not, through the sample. As opposed to ghost imaging, entanglement plays an essential role in this case, as does the entangling detection procedure, consisting in projecting the final state on a Bell-state basis. For isotropic depolarization, quantum advantage is obtained only when the final state, after interaction with the sample, is not entangled anymore.

DOI
10.1117/12.2655636

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Quantum ghost imaging harnesses entangled photon pairs to form images using light that never directly interacts with the object. Conventional approaches rely on pixelated detectors or spatial masks, where the resolution is fundamentally limited by the pixel size and thus bounded by the Rayleigh criterion. In this work, we present a modal approach that replaces pixel-based detection with measurements in a basis of structured modes. By reconstructing images through tailored spatial modes, we decouple resolution from the physical limitations of detectors and instead tie it to the system’s optical precision and computational control. We demonstrate that even non-orthogonal modal sets can achieve high fidelity image reconstruction by exploiting modal sparsity, significantly reducing the number of required measurements. Using phase-only approximations of Hermite-Gaussian modes, we avoid the loss associated with complex amplitude modulation while retaining high reconstruction fidelity. The result is a high-resolution, high-efficiency quantum ghost imaging technique powered by structured light, opening new possibilities for photon-efficient imaging in low-light and quantum-limited regimes, such as biological microscopy and remote sensing.
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We compare the performance of quantum imaging schemes based on spatially correlated photon pairs by formulating them as quantum multiparameter estimation problems, in which the object is characterized by transmission coefficients associated with different spatial modes. Our work focuses on standard quantum imaging techniques such as ghost imaging, two-photon imaging, and imaging with undetected photons. Specifically, we compute the quantum Fisher information matrices and show that they are saturated by Fisher information matrices corresponding to measurements in the object-mode basis, which generalize the common detection schemes employed in each imaging configuration. We find that ghost imaging and two-photon imaging generally provide higher precision for transmission estimation than imaging with undetected photons, but the latter is the only one that naturally does not couple transmission estimation across different spatial modes. These results identify which imaging protocols are best suited for specific tasks and provide practical guidelines for the design and optimization of quantum sensing technologies based on spatial correlations.