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arXiv:2112.12102 · Physical Review Applied

Ultimate Quantum Sensitivity in the Estimation of the Delay between two Interfering Photons through Frequency-Resolving Sampling

Danilo Triggiani, Giorgos Psaroudis, Vincenzo Tamma

Published Apr 24, 2023• 26 citations
arXivHTMLPDF

Abstract

We demonstrate the ultimate sensitivity allowed by quantum physics in the estimation of the time delay between two photons by measuring their interference at a beam splitter through frequency-resolving sampling measurements. This sensitivity can be increased quadratically by decreasing the photonic temporal bandwidth even at values smaller than the time delay when standard two-photon interferometers become inoperable and without adapting the path of the reference photon, nor the need of time-resolving detectors with an unfeasible high resolution. Applications can range from the more feasible imaging of nanostructures, including biological samples, and nanomaterial surfaces to quantum enhanced estimation based on frequency-resolved boson sampling in optical networks.

DOI
10.1103/physrevapplied.19.044068

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Optical sensing schemes based on two-photon interference offer a powerful platform for precision metrology, but are usually limited by a trade-off between dynamic range and measurement precision. Here, we overcome this limitation by resolving the frequency of two photons impinging on a beam splitter and combining these measurements with a new estimation strategy. This increases the usable dynamic range by up to a factor of 20 compared with conventional frequency nonresolved schemes. We implement the method with independent photon pair sources and characterize its performance in the presence of finite-resolution frequency-resolved detectors, which approach the quantum limit in the lossless regime. Our approach enables scan-free, nanometer resolution depth sensing over millimeter scale distances, with potential applications in biological and nanomaterial imaging.
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We present a quantum sensing scheme achieving the ultimate quantum sensitivity in the estimation of the transverse displacement between two photons interfering at a balanced beam splitter, based on transverse-momentum sampling measurements at the output. This scheme can possibly lead to enhanced high-precision nanoscopic techniques, such as superresolved single-molecule localization microscopy with quantum dots, by circumventing the requirements in standard direct imaging of camera resolution at the diffraction limit, and of highly magnifying objectives. Interestingly, we show that our interferometric technique achieves the ultimate spatial precision in nature irrespectively of the overlap of the two displaced photonic wave packets, while its precision is only reduced of a constant factor for photons differing in any nonspatial degrees of freedom. This opens a new research paradigm based on the interface between spatially resolved quantum interference and quantum-enhanced spatial sensitivity.
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Abstract A two-photon interfering technique based on polarization-resolved measurements is presented for the simultaneous estimation with maximum quantum sensitivity of multiple parameters associated with the polarization state of two interfering photonic qubits. This estimation is achieved by exploiting a novel interferometric technique based on polarization-resolved two-photon interference. The experimental feasibility and accuracy of this technique is shown, even when a limited number of sampling measurements is employed. This work is relevant for the development of quantum technologies with photonic qubits and sheds light on the physics at the interface between multiphoton interference, boson sampling, multi-parameter quantum sensing, and quantum information processing.