We introduce a holographic imaging concept that is conditioned on photonic entanglement. We show that entanglement-encoded phase images can be retrieved through dynamic phase disorder and in the presence of classical noise, with practical advantage over classical holography.
Holography encodes information using classical light interference with applications ranging from microscopy to data storage. Quantum entanglement enables information processing with capabilities beyond technology based on classical principles. Here we introduce a holographic imaging concept that is conditioned on the coherence, and thus the entanglement, between the qubit terms in a quantum entangled photon state. By harnessing the nonlocal properties of entanglement, we remotely reconstruct an image encoded in the phase of spatial-polarisation hyper-entangled photons. The nonlocal nature of our measurements removes the need for path overlap, resulting in insensitivity to mechanical instabilities, while polarisation encoding provides robustness against random phase disorder. Furthermore, the measurement of correlations removes the sensitivity to the presence of stray light.
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.
This study investigates quantum holography, emphasizing its capability to conduct holographic imaging without the requirement for first-order coherence—a limitation of classical physics. By harnessing quantum entanglement, where image data is embedded in the phase correlation of polarization-entangled photon pairs and spread across the transverse spatial dimension, quantum holography enhances imaging performance. This technique not only improves resolution for polarization-sensitive phase objects but also provides resilience against stochastic phase fluctuations and uncontrolled ambient light, offering significant tangible benefits compared to conventional holography. Additionally, its integration with quantum tomography enables precise analysis of multi-dimensional hyper-entangled states, advancing quantum state analysis. Although current challenges remain, such as extended acquisition times due to technological constraints, ongoing advancements in faster, more affordable sensors are expected to address these issues. As a result, quantum holography is poised to have broad applications in biological imaging, sensing, and the exploration of complex high-dimensional quantum states. These developments position quantum holography as a crucial technology in the future of quantum optical communication and information processing, driving innovation and opening new avenues in these fields.
The retrieval of the phase with single-photon states is a fundamentally and technically challenging endeavor. Here we report an experimental realization of hologram recordings with heralded single-photon illumination and continuous observation of photon statistics. Thereby, we demonstrate the basic principle of holography with single-photon states which cannot be described with the classical wave theory. Under conditions with illumination more than 200 times weaker than the noise of the detector, a hologram (interferogram) recorded with a heralded single-photon source revealed an object not visible with nonheralded illumination and slightly higher intensity. The dramatic improvement in retrieval of amplitude and phase information achieved with the heralded single-photon source can be explained by the strong suppression of noise due to the nonclassical temporal correlation between twin photons and the small coincidence time window. The method could be useful for recording and retrieving amplitude and phase information in the presence of strong noise, for covert imaging, and for imaging of photosensitive biological and material samples.