Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2508.19978 · Quantum Science and Technology

Momentum-resolved two photon interference of weak coherent states

Fabrizio Sgobba, Francesco Di Lena, Danilo Triggiani, Deborah Katia Pallotti, Cosmo Lupo, Piergiorgio Daniele, Gennaro Fratta, Giulia Acconcia, Ivan Rech, Luigi Santamaria Amato

Published Nov 26, 2025• 0 citations
arXivHTMLPDF

Abstract

Abstract We demonstrate an experimental scheme for high-precision position measurements based on transverse-momentum-resolved two-photon interferometry with independent photons and single photon avalanche diode (SPAD) arrays. Our scheme extends the operative range of Hong–Ou–Mandel interferometry beyond its intrinsic constraints due to photons indistinguishability, paving the way to applications in high-resolution imaging. We assess the experimental results against the ultimate precision bounds as determined by quantum estimation theory. Our experiment ultimately proves that transverse-momentum resolved measurements of fourth-order correlations in the fields can be employed to overcome spatial distinguishability between independent photons. The relevance of our results extends beyond sensing and imaging towards quantum information processing, as we show that partial photon distinguishability and entanglement impurity are not necessarily a nuisance in a technique that relies on two-photon interference.

DOI
10.1088/2058-9565/ae24a7

Related papers

Ultrasensitive transverse deflection measurement with two-photon interference

Chaojie Wang, Yuning Zhang, Yuanyuan Chen +1 more

Hong-Ou-Mandel (HOM) interference is an intrinsic quantum phenomena that goes beyond the possibilities of classical physics, and enables various applications in quantum metrology. While the timing resolution of HOM-based sensor is generally investigated, the ultimate quantum sensitivity in the estimation of transverse deflection or displacement between paired photons interfering at a balanced beam splitter has been explored relatively little. Here, we present an experimental demonstration of a spatial HOM interferometry for measuring the transverse deflection of an optical beam by using transverse momentum sampling measurements. This feasible scheme suffices to achieve great precision with comparatively little technological effort, which circumvents the stringent requirement in direct imaging resolution at the diffraction limit. We can adaptively determine optimum working points using a Fisher information analysis, and demonstrate an optimized spatial HOM interferometry according to practical applications. These results may significantly facilitate the use of quantum interference for high precision spatial sensing, and pave the way to more complex quantum imaging techniques like nanoscopic microscopy.

arXiv:2504.04397•Physical Review Applied•Dec 9, 2025•0 citations

Estimation with Ultimate Quantum Precision of the Transverse Displacement between Two Photons via Two-Photon Interference Sampling Measurements

Danilo Triggiani, Vincenzo Tamma

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.

arXiv:2309.06883•Physical Review Letters•Apr 30, 2024•20 citations

Observation of two-photon interference effect with a single non-photon-number resolving detector

Heonoh Kim, Sang Min Lee, Osung Kwon +1 more

Multiphoton interference effects can be measured with a single detector when two input photons are temporally well separated when compared with the dead time of the single-photon avalanche detector. Here we experimentally demonstrate that the Hong-Ou-Mandel interference effect can be observed with a single non-photon-number resolving detector via a time-delayed coincidence measurement of successive electrical signals from the detector. The two-photon interference experiment is performed by utilizing temporally well-separated pairwise weak coherent pulses, and the interference fringes are successfully measured with high visibility in the range of the limited upper bound for the weak coherent photon source.

arXiv:1706.03588•Optics Letters•Jun 15, 2017•8 citations

Generalized quantum interference of correlated photon pairs

Heonoh Kim, Sang Min Lee, Han Seb Moon

Superposition and indistinguishablility between probability amplitudes have played an essential role in observing quantum interference effects of correlated photons. The Hong-Ou-Mandel interference and interferences of the path-entangled photon number state are of special interest in the field of quantum information technologies. However, a fully generalized two-photon quantum interferometric scheme accounting for the Hong-Ou-Mandel scheme and path-entangled photon number states has not yet been proposed. Here we report the experimental demonstrations of the generalized two-photon interferometry with both the interferometric properties of the Hong-Ou-Mandel effect and the fully unfolded version of the path-entangled photon number state using photon-pair sources, which are independently generated by spontaneous parametric down-conversion. Our experimental scheme explains two-photon interference fringes revealing single- and two-photon coherence properties in a single interferometer setup. Using the proposed interferometric measurement, it is possible to directly estimate the joint spectral intensity of a photon pair source.

arXiv:1503.08611•Scientific Reports•May 7, 2015•21 citations

Full-field quantum imaging with a single-photon avalanche diode camera

Hugo Defienne, Jiuxuan Zhao, Edoardo Charbon A +1 more

Single-photon avalanche diode (SPAD) arrays are essential tools in biophotonics, optical ranging and sensing, and quantum optics. However, their small number of pixels, low quantum efficiency, and small fill factor have so far hindered their use for practical imaging applications. Here, we demonstrate full-field entangled photon-pair correlation imaging using a 100-kpixel SPAD camera. By measuring photon coincidences between more than 500 million pairs of positions, we retrieve the full point spread function of the imaging system and subsequently high-resolution images of target objects illuminated by spatially entangled photon pairs. We show that our imaging approach is robust against stray light, enabling quantum imaging technologies to move beyond laboratory experiments towards real-world applications such as quantum light detection and ranging.

arXiv:2007.16037•Physical Review A•Apr 13, 2021•40 citations

On complexity in spatially resolved multi-photon interference

Miguel Ángel Gonz’alez Jaimes

Multi-photon interference is the foundation of many applications regarding quantum technologies. Notably, the interference of multiple photons, registered using resolved measurements, is related to the permanent of a matrix, a problem known to be a #P-hard task. Traditionally, achieving high-visibility interference requires a high degree of indistinguishability between the interfering photons. However, this restriction can be circumvented by observing interference in the conjugate variables. This method has been successfully demonstrated using resolved measurements in the temporal and frequency domain. In this work, we extend these approaches to the spatial degrees of freedom of light. Theoretically, we demonstrate that the joint probability of detecting two photons at different positions in the output ports (3 and 4) of a beam-splitter is indeed determined by the permanent of a matrix related to the unitary transformation described by the interferometer. From an experimental perspective, we present experimental results for spatially-resolved interference in position for photons that are distinguishable in transverse momentum. We employ a setup to perform spatially-resolved measurements on photons with an adjustable distinguishability in both the central transverse momentum variable and the lateral displacement from the optical axis. This setup provides full simultaneous tunability over the distinguishability in the spatial variables. Additionally, by varying the lateral displacement, we observe how distinguishability in the position impacts the interference pattern. Overall, our results align well with the theoretical model, reinforcing the validity of our approach. Thus, this work offers new insights into the available degrees of freedom for studying of multi-photonic interference and its applications.

•Jan 30, 2025•0 citations
Abstract We demonstrate an experimental scheme for high-precision position measurements based on transverse-momentum-resolved two-photon interferometry with independent photons and single photon avalanche diode (SPAD) arrays. Our scheme extends the operative range of Hong–Ou–Mandel interferometry beyond its intrinsic constraints due to photons indistinguishability, paving the way to applications in high-resolution imaging. We assess the experimental results against the ultimate precision bounds as determined by quantum estimation theory. Our experiment ultimately proves that transverse-momentum resolved measurements of fourth-order correlations in the fields can be employed to overcome spatial distinguishability between independent photons. The relevance of our results extends beyond sensing and imaging towards quantum information processing, as we show that partial photon distinguishability and entanglement impurity are not necessarily a nuisance in a technique that relies on two-photon interference.
Hong-Ou-Mandel (HOM) interference is an intrinsic quantum phenomena that goes beyond the possibilities of classical physics, and enables various applications in quantum metrology. While the timing resolution of HOM-based sensor is generally investigated, the ultimate quantum sensitivity in the estimation of transverse deflection or displacement between paired photons interfering at a balanced beam splitter has been explored relatively little. Here, we present an experimental demonstration of a spatial HOM interferometry for measuring the transverse deflection of an optical beam by using transverse momentum sampling measurements. This feasible scheme suffices to achieve great precision with comparatively little technological effort, which circumvents the stringent requirement in direct imaging resolution at the diffraction limit. We can adaptively determine optimum working points using a Fisher information analysis, and demonstrate an optimized spatial HOM interferometry according to practical applications. These results may significantly facilitate the use of quantum interference for high precision spatial sensing, and pave the way to more complex quantum imaging techniques like nanoscopic microscopy.
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.
Multiphoton interference effects can be measured with a single detector when two input photons are temporally well separated when compared with the dead time of the single-photon avalanche detector. Here we experimentally demonstrate that the Hong-Ou-Mandel interference effect can be observed with a single non-photon-number resolving detector via a time-delayed coincidence measurement of successive electrical signals from the detector. The two-photon interference experiment is performed by utilizing temporally well-separated pairwise weak coherent pulses, and the interference fringes are successfully measured with high visibility in the range of the limited upper bound for the weak coherent photon source.
Superposition and indistinguishablility between probability amplitudes have played an essential role in observing quantum interference effects of correlated photons. The Hong-Ou-Mandel interference and interferences of the path-entangled photon number state are of special interest in the field of quantum information technologies. However, a fully generalized two-photon quantum interferometric scheme accounting for the Hong-Ou-Mandel scheme and path-entangled photon number states has not yet been proposed. Here we report the experimental demonstrations of the generalized two-photon interferometry with both the interferometric properties of the Hong-Ou-Mandel effect and the fully unfolded version of the path-entangled photon number state using photon-pair sources, which are independently generated by spontaneous parametric down-conversion. Our experimental scheme explains two-photon interference fringes revealing single- and two-photon coherence properties in a single interferometer setup. Using the proposed interferometric measurement, it is possible to directly estimate the joint spectral intensity of a photon pair source.
Single-photon avalanche diode (SPAD) arrays are essential tools in biophotonics, optical ranging and sensing, and quantum optics. However, their small number of pixels, low quantum efficiency, and small fill factor have so far hindered their use for practical imaging applications. Here, we demonstrate full-field entangled photon-pair correlation imaging using a 100-kpixel SPAD camera. By measuring photon coincidences between more than 500 million pairs of positions, we retrieve the full point spread function of the imaging system and subsequently high-resolution images of target objects illuminated by spatially entangled photon pairs. We show that our imaging approach is robust against stray light, enabling quantum imaging technologies to move beyond laboratory experiments towards real-world applications such as quantum light detection and ranging.
Multi-photon interference is the foundation of many applications regarding quantum technologies. Notably, the interference of multiple photons, registered using resolved measurements, is related to the permanent of a matrix, a problem known to be a #P-hard task. Traditionally, achieving high-visibility interference requires a high degree of indistinguishability between the interfering photons. However, this restriction can be circumvented by observing interference in the conjugate variables. This method has been successfully demonstrated using resolved measurements in the temporal and frequency domain. In this work, we extend these approaches to the spatial degrees of freedom of light. Theoretically, we demonstrate that the joint probability of detecting two photons at different positions in the output ports (3 and 4) of a beam-splitter is indeed determined by the permanent of a matrix related to the unitary transformation described by the interferometer. From an experimental perspective, we present experimental results for spatially-resolved interference in position for photons that are distinguishable in transverse momentum. We employ a setup to perform spatially-resolved measurements on photons with an adjustable distinguishability in both the central transverse momentum variable and the lateral displacement from the optical axis. This setup provides full simultaneous tunability over the distinguishability in the spatial variables. Additionally, by varying the lateral displacement, we observe how distinguishability in the position impacts the interference pattern. Overall, our results align well with the theoretical model, reinforcing the validity of our approach. Thus, this work offers new insights into the available degrees of freedom for studying of multi-photonic interference and its applications.