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Applied Physics Letters

Scanning biphoton phase imaging with enhanced signal-to-noise ratio for quantum holography

Jing Gao, Jing Wang, Wen-Zheng Zhu, Shuang‐Yin Huang, Zi-Mo Cheng, Shu-Tian Xue, Li-Ping Yang, Zhi-Cheng Ren, Xi‐Lin Wang, Hui‐Tian Wang

Published May 4, 2026• 0 citations
Publisher

Abstract

Biphoton phase imaging via two-photon coincidence detection is essential for quantum holography and related quantum imaging applications. Although camera-based methods have been predominantly used in previous studies, we here introduce a two-dimensional scanning method for biphoton phase imaging in quantum holography, which leverages a high-efficiency single-photon detector, improving signal-to-noise ratio (SNR). Using this platform, we obtained a quantum holographic phase image with an SNR above 19 and experimentally verified the noise-resilient nature of quantum holography under scanning-based detection. By using the brighter quantum sources, our method offers an efficient route toward faster two-photon coincidence imaging, which is expected to facilitate broader applications of quantum imaging in noisy environments.

DOI
10.1063/5.0325971

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Biphoton phase imaging via two-photon coincidence detection is essential for quantum holography and related quantum imaging applications. Although camera-based methods have been predominantly used in previous studies, we here introduce a two-dimensional scanning method for biphoton phase imaging in quantum holography, which leverages a high-efficiency single-photon detector, improving signal-to-noise ratio (SNR). Using this platform, we obtained a quantum holographic phase image with an SNR above 19 and experimentally verified the noise-resilient nature of quantum holography under scanning-based detection. By using the brighter quantum sources, our method offers an efficient route toward faster two-photon coincidence imaging, which is expected to facilitate broader applications of quantum imaging in noisy environments.
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Single-photon-sensitive cameras can now be used as massively parallel coincidence counters for entangled photon pairs. This enables measurement of biphoton joint probability distributions with orders-of-magnitude greater dimensionality and faster acquisition speeds than traditional raster scanning of point detectors; to date, however, there has been no general formula available to optimize data collection. Here we analyze the dependence of such measurements on count rate, detector noise properties, and threshold levels. We derive expressions for the biphoton joint probability distribution and its signal-to-noise ratio (SNR), valid beyond the low-count regime up to detector saturation. The analysis gives operating parameters for global optimum SNR that may be specified prior to measurement. We find excellent agreement with experimental measurements within the range of validity and discuss discrepancies with the theoretical model for high thresholds. This work enables optimized measurement of the biphoton joint probability distribution in high-dimensional joint Hilbert spaces.
Abstract High-dimensional biphoton states are promising resources for quantum applications, ranging from high-dimensional quantum communications to quantum imaging. A pivotal task is fully characterizing these states, which is generally time-consuming and not scalable when projective measurement approaches are adopted; however, new advances in coincidence imaging technologies allow for overcoming these limitations by parallelizing multiple measurements. Here we introduce biphoton digital holography, in analogy to off-axis digital holography, where coincidence imaging of the superposition of an unknown state with a reference state is used to perform quantum state tomography. We apply this approach to single photons emitted by spontaneous parametric down-conversion in a nonlinear crystal when the pump photons possess various quantum states. The proposed reconstruction technique allows for a more efficient (three orders of magnitude faster) and reliable (an average fidelity of 87%) characterization of states in arbitrary spatial modes bases, compared with previously performed experiments. Multiphoton digital holography may pave the route toward efficient and accurate computational ghost imaging and high-dimensional quantum information processing.
Quantum imaging with undetected light has recently emerged as a technique in which quantum correlations and nonlinear interferometry are combined to decouple illumination and detection paths. This approach has been more recently extended and combined with digital phase-shifting holography and off-axis holography to extract both the amplitude and phase information of a sample relying on single-photon interference. Despite these advantages, implementing the technique in real-world scenarios where the observed system is subject to environmental noise and dynamic variations remains challenging. The primary limitation lies in the inability of quantum imaging systems to retrieve object information in real time under high-noise conditions. Here, we experimentally demonstrate real-time amplitude and phase imaging in noisy environments, building upon our previous implementation of quantum off-axis holography. Our results demonstrate real-time imaging at acquisition rates up to 4~Hz, even when the noise level exceeds the signal by an order of magnitude.
Quantum imaging usually refers to imaging that takes advantage of quantum entanglement to obtain results beyond the classically achievable limits [1]. Various complex experimental setups are used to obtain quantum images, and even more complex experimental setups are used when the goal is to record and retrieve the phase information of the object. Classical holography offers the possibility to record and retrieve phase information from a hologram [2]. However, in low-light conditions, a major challenge is to record images with a high signal-to-noise ratio. Classical schemes [3]–[5], of course, do not aim to demonstrate the quantum properties of the experiments, and quantum schemes [6]–[8] rely on complex preparation of the light beam and do not necessarily provide an advantage for holographic imaging. To date, no simple quantum scheme with quantum advantage has been developed for low-light holographic imaging.