Abstract
We report the experimental observation of a spatiotemporal Hong-Ou-Mandel (HOM) interference of biphoton states of extremely high Schmidt number. Two-photon interference of 1500 spatial modes and a total of more than spatiotemporal modes is evidenced by measuring momentum spatial coincidences, without any prior selection of the photons in time and space coincidence, between the pixels of the far-field images of two strongly multimode spontaneous parametric down-conversion (SPDC) beams propagating through a HOM interferometer. The outgoing SPDC beams are recorded on two separate detector arrays operating in the photon-counting regime. The properties of HOM interference are investigated both in the time and space domains. We show that the two-photon interference exhibits temporal and two-dimensional spatial HOM dips with visibilities of 60% and widths in good agreement with the spatiotemporal coherence properties of the biphoton state. Moreover, we demonstrate that maxima of momentum spatial coincidences are evidenced within each image, in correspondence with these dips.
- Received 18 February 2020
- Revised 17 April 2020
- Accepted 11 June 2020
DOI:https://doi.org/10.1103/PhysRevX.10.031031
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
In a crystal, photons of a laser beam can split into entangled pairs of lower-frequency photons that form a single quantum object. If this pair is sent to a beam splitter, they exit randomly but on the same output port, a phenomenon known as Hong-Ou-Mandel (HOM) two-photon interference. HOM interference is used in novel communication protocols, such as quantum teleportation and quantum information processing, but without spatial resolution, because of the use of single-pixel detectors. However, entanglement concerns all properties of twin photons, including their position in space and time. Here, we obtain HOM interference for thousands of spatial, as well temporal, resolution cells, resulting in a total spatiotemporal dimensionality of .
In our HOM interferometer, spatial coincidences at the output ports are imaged on two cameras operating in photon-counting mode. Since we control the indistinguishability between the photons of a pair in time, space, polarization, and wavelength, we observe and quantify HOM interference spatially and temporally at the quantum level of more than 4000 photon pairs.
Given the essential role played by two-photon HOM interference in most of the systems developed for quantum information processing, demonstrating that HOM interference can be obtained by manipulating quantum states of giant dimensionality opens the way for the development of very-high-dimensional quantum information protocols using space and time variables.
