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Correlated photons from parametric down-coversion driven by a CW laser are used for time- and frequency-resolved spectroscopy, enabling sub-second acquisition times on biological samples and single-photon excitation of photosynthetic processes.

Waveguides—often based on total internal reflection—underpin many photonic technologies, including fibre networks for broadband communications. Now a different type of waveguide based on physical diffusion in a scattering medium is demonstrated.

Ultrafast imaging schemes can enable a diverse range of applications but require long acquisition times or raster scanning. Here, Gariepy et al. demonstrate visualization and rapid characterization of light-in-flight and laser-induced plasma formation using single-photon detector arrays.

Understanding the nature of coherent absorption is essential for exploiting it in new technologies. Here, the authors show that a metamaterial can deterministically absorb photons from a travelling wave with nearly unitary probability, down to the single-photon level.

Steady state visually evoked potentials enable EEG vision-based brain computer interfaces. We show that it is possible to encode information distributed across 100+ frequencies. We encode images and perform simple physical computing classification tasks. Connecting more than one in brain in series improves the classification capability.

The optical transmission of images through a multimode fibre remains an outstanding challenge. Here, the authors implement a method that statistically reconstructs the inverse transformation matrix for a fibre and demonstrate real-time imaging of natural scenes in full colour, high resolution and high frame rate.

Acoustic waves that carry orbital angular momentum are amplified as they pass through an absorbing disk when the rotation rate exceeds the frequency of the incident wave, thus providing an experimental demonstration of Zel’dovich amplification.

Ghost imaging allows the creation of images using light that never interacts with the object. Researchers now show that this technique can be applied to reconstruct temporal 'images' of rapidly varying, picosecond signals in telecommunication systems.

Optical non-line-of-sight imaging demands ultrafast detectors and suffers steep power loss, limiting range and practicality. Here, the authors realize a phase-sensitive synthetic-aperture ultrasound platform that exploits specular wall reflections and f-k migration to reconstruct 3D hidden scenes with 1 cm lateral resolution at meter-scale ranges, attaining performance comparable to optical approaches with low-power, eye-safe hardware.

Nonlocal, nonlinear interactions of optical beams can be described by the Newton–Schrödinger equation for quantum gravity, offering an analogue for studying gravitational phenomena.

Standard techniques for Fluorescence Lifetime Imaging Microscopy are limited by the electronics to 100’s of picoseconds time resolution. Here, the authors show how to use two-photon interference to perform fluorescence lifetime sensing with picosecond-scale resolution.

Pixelation is common in quantum imaging systems and limit the image spatial resolution. Here, the authors introduce a pixel super-resolution approach based on measuring the full spatially-resolved joint probability distribution of spatially-entangled photons, and improve pixel resolution by a factor two.

By exploiting polarization entanglement between photons, quantum holography can circumvent the need for first-order coherence that is vital to classical holography.

Hong–Ou–Mandel interference enables depth-resolved quantum imaging at very low light levels.

A convolutional network that approaches the fundamental Cramér–Rao bound is demonstrated to localize a reflective target hidden behind a dynamically fluctuating scattering medium, advancing algorithmic developments in the field of computational imaging.

By combining a single-photon time-of-flight camera with computational processing of the spatial and full temporal photon distribution data, an object embedded inside a strongly diffusive medium can be imaged over more than 80 transport mean free paths in a contactless manner on the timescale of the order of 1 s.

The evolution of modulational instability sidebands in an optical fibre are shown to provide new insights into Fermi–Pasta–Ulam–Tsingou recurrences.

In the weak field limit, boson star evolution is governed by the Newton-Schrödinger equation. Here the authors report an optical setup that provides a formal analogue of such dynamics via the interaction between vortex beams and a medium with positive thermo-optical nonlinearity.

Scientists demonstrate an experimental method that allows them to locate and track moving targets that are hidden from the direct line of sight, for example, by a wall or an obstacle, with only a few seconds acquisition time and centimetre precision.

Observing the dynamical Casimir effect, where two particles are generated from the vacuum, is challenging in the optical regime due to its purely-temporal nature. The authors demonstrate a dispersion-oscillating fibre system operating in the near-infrared regime and capable of resolving correlated photon pairs as an analogue to the dynamical Casimir effect.

Entanglement swapping in high dimensions requires large numbers of entangled photons and consequently suffers from low photon flux. Here the authors demonstrate entanglement swapping of multiple spatial modes of light simultaneously, without the need for increasing the photon numbers with dimension.

Non-line-of-sight (NLOS) imaging methods use light scattered from multiple surfaces to reconstruct images of scenes that are hidden by another object. This Perspective summarizes existing NLOS imaging techniques and discusses which directions show most promise for future developments.

Large structure in the Universe, such as galaxies, are believed to form by a process called violent relaxation, which occurs over millions of years. The authors present a nonlinear optics experiment which shows direct observation of violent relaxation, whose evolution can be related to the equations governing galaxy formation.

This Review provides an overview of the most recently developed quantum imaging systems, highlighting the nonclassical properties of sources, such as bright squeezed light, entangled photons and single-photon emitters that enable their functionality.