Scintillation, the process of converting high-energy radiation into detectable visible light underpins technologies from medical imaging to particle physics, yet conventional scintillators are limited by the oscillator strength of their individual emission centers. Here, we propose and demonstrate quantum optical scintillators, showcasing collective scintillation under X-ray excitation, where quantum correlations between emitters accelerate their emission beyond the intrinsic individual-oscillator rate. The effect appears as a red-shifted spectral peak and an enhanced emission rate, with an average lifetime of 230 ps at 80 K, 14× faster than room-temperature spontaneous emission. Unlike UV-driven superfluorescence, each X-ray photon generates a photoelectron that excites multiple neighboring, coupled quantum dots, producing a faster rate, larger spectral shift, and broader spectrum. We characterize the temperature-dependent temporal response using a Hanbury-Brown-Twiss g(2)(τ) setup. A many-body quantum-optics theory reproduces both UV- and X-ray-driven regimes. These quantum enhancements surpass emission-rate limits and could substantially improve time-of-flight detector performance.

Photonic quantum computing has been rapidly advancing over the past decade, with measurement-based approaches emerging as particularly promising. A crucial requirement for these approaches is the generation of large-scale cluster states. In this work, we present a method to create cluster states using Photonic Time-Crystals (PTCs) — dielectric materials with their refractive index rapidly modulated in time. PTCs effectively function as a set of optical parametric oscillators and beam-splitters, producing simultaneous two-mode squeezing for many pairs of photonic modes with opposite wavevectors. We utilize this capability to propose a method for generating two-dimensional cluster states, offering important advantages over existing protocols.

The generation and control of extreme ultraviolet (XUV) radiation by high harmonic generation (HHG) have advanced ultrafast science, providing direct insights into electron dynamics on their natural time scale. Attosecond science has established the capability to resolve ultrafast quantum phenomena in matter by characterizing and controlling the classical properties of the high harmonics. Recent theoretical proposals have introduced novel schemes for generating and manipulating XUV HHG with distinct quantum features, paving the way to attosecond quantum optics. In this work, we transfer fundamental concepts in quantum optics into attosecond science. By driving the HHG process with a combination of an infrared bright squeezed vacuum (BSV, a non-classical state of light), and a strong coherent field, we imprint the quantum correlations of the input BSV onto both the ultrafast electron wavefunction and the harmonics' field. Performing in-situ HHG interferometry provides an insight into the underlying sub-cycle dynamics, revealing squeezing in the statistical properties of one of the most fundamental strong-field phenomena – field induced tunneling. Our measurement allows the reconstruction of the quantum state of the harmonics through homodyne-like tomography, resolving correlated fluctuations in the harmonic field that mirror those of the input BSV. By controlling the delay between the two driving fields, we manipulate the photon statistics of the emitted attosecond pulses with sub-cycle accuracy. The ability to measure and control quantum correlations in both electrons and XUV attosecond pulses establishes a foundation for attosecond electrodynamics, manipulating the quantum state of electrons and photons with sub-cycle precision.

We present the first observation of non-perturbative high-harmonic generation driven by nonclassical light, namely bright squeezed vacuum. Compared to classical light, bright squeezed vacuum leads to higher efficiency, different power scaling, and unique photon-number distributions.

High-harmonic generation has been driving the development of attosecond science and sources. More recently, high-harmonic generation in solids has been adopted by other communities as a method to study material properties. However, so far high-harmonic generation has only been driven by classical light, despite theoretical proposals to do so with quantum states of light. Here we observe non-perturbative high-harmonic generation in solids driven by a macroscopic quantum state of light, a bright squeezed vacuum, which we generate in a single spatiotemporal mode. The process driven by a bright squeezed vacuum is considerably more efficient in the generation of high harmonics than classical light of the same mean intensity. Due to its broad photon-number distribution, covering states from 0 to 2 x 1013 photons per pulse, and strong subcycle electric field fluctuations, a bright squeezed vacuum gives access to free carrier dynamics within a much broader range of peak intensities than accessible with classical light. High-harmonic generation has so far been driven only by classical light. Now, its driving by a bright squeezed vacuum-a quantum state of light-has been observed and shown to be more efficient than using classical light.

For decades, most research of high harmonic generation (HHG) considered matter as quantum but light as classical. Recently, HHG driven by quantum states of light such as bright squeezed vacuum was predicted to reach beyond the classical HHG cutoff. Moreover, in squeezed coherent illumination, it was shown that the underlying dynamics are significantly modified by the photon statistics effective force. Here we show that HHG driven by quantum light results in quantum high harmonics. We derive a formula for the quantum state of the high harmonics, when driven by arbitrary quantum light states, and then explore specific cases of experimental relevance. Specifically, for a moderately squeezed pump, HHG driven by squeezed coherent light results in squeezed high harmonics. Harmonic squeezing is optimized by syncing ionization times with the pump's squeezing phase. Beyond this regime, as pump squeezing is increased, the harmonics initially acquire squeezed thermal photon statistics, and then occupy an intricate quantum state which strongly depends on the semiclassical nonlinear response function of the interacting system. Our results pave the way for generation of squeezed extreme-ultraviolet ultrashort pulses, and more generally, quantum frequency conversion into previously inaccessible spectral ranges, which may enable ultrasensitive attosecond metrology.

We demonstrate experimentally high-speed ptychographic imaging of non-repetitive complex-valued events. Three time-resolved complex-valued frames are reconstructed from data recorded in a single camera snapshot. The temporal resolution of the microscope is determined by delays between illuminating pulses. The ability to image amplitude and phase of nonrepetitive events with ultrafast temporal resolution will open new opportunities in science and technology.

We develop a framework describing quantum noise propagation in highly spatially multimode nonlinear optical systems. We predict quantum deviations of the spatial intensity noise distribution from the spatial power distribution, and observe this effect experimentally.

We used a single-shot ptychographic microscope to image the complex-valued (intensity and phase) spatial profiles of multiple ultrashort pulses. Specifically, we present a characterization of a burst of three ultrashort pulses with three nanoseconds delays between pulses using data recorded by a single camera exposure with millisecond integration time. This scheme is promising for various applications, including characterizing spatiotemporal mode-locked or Q-switched lasers, potentially shedding light on their buildup dynamics.

Structured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields are inhomogeneous and cannot be approximated by a single plane wave. Even the interference of two plane waves, or of a single inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and additional functionalities as compared to a single plane wave. Complex wavefields with inhomogeneities in the amplitude, phase, and polarization, including topological----- structures and singularities, underpin modern nanooptics and photonics, yet they are equally important, e.g. for quantum matter waves, acoustics, water waves, etc. Structured waves are crucial in optical and electron microscopy, wave propagation and scattering, imaging, communications, quantum optics, topological and non-Hermitian wave systems, quantum condensed-matter systems, optomechanics, plasmonics and metamaterials, optical and acoustic manipulation, and so forth. This Roadmap is written collectively by prominent researchers and aims to survey the role of structured waves in various areas of wave physics. Providing background, current research, and anticipating future developments, it will be of interest to a wide cross-disciplinary audience.

We study how thermodynamic behavior in classical nonlinear optical multimode systems presents itself in quantum many-body settings, and find multimode entanglement arising in the thermalization process.

Using a single-shot ptychographic microscope, we image the complex-valued spatial profiles of ultrashort pulses of an isolated laser pulse burst. It shows that this system can film ultrafast non-repetitive complex-valued events.

For decades, most research on high harmonic generation (HHG) considered matter as quantum but light as classical, leaving the quantum-optical nature of the harmonics an open question. Here we explore the quantum properties of high harmonics. We derive a formula for the quantum state of the high harmonics, when driven by arbitrary quantum light states, and then explore specific cases of experimental relevance. Specifically, for a moderately squeezed pump, HHG driven by squeezed coherent light results in squeezed high harmonics. Harmonic squeezing is optimized by syncing ionization times with the pump's squeezing phase. Beyond this regime, as pump squeezing is increased, the harmonics initially acquire squeezed thermal photon statistics, and then occupy an intricate quantum state which strongly depends on the semi-classical nonlinear response function of the interacting system. Our results pave the way for the generation of squeezed extreme-ultraviolet ultrashort pulses, and, more generally, quantum frequency conversion into previously inaccessible spectral ranges, which may enable ultrasensitive attosecond metrology.

We predict and demonstrate a novel effective force exerted on matter when illuminated by light with non-classical photon-statistics. For squeezed-vacuum irradiation, the photon-statistics force stretches and squeezes matter wavefunctions, leading to emission of squeezed-vacuum harmonics.

We show that extreme-nonlinear optics transfers quantum states of light between spectral ranges. We demonstrate high harmonic generation driven by squeezed light results in squeezed harmonics, and explore the dispersion & criticality of harmonic squeezing.

We build a quantum optical theory of strongly-driven many-body systems. We find that quantum correlated emitters result in strongly nonclassical emission, opening a new path towards generating quantum light and characterizing quantum correlated matter.

High-harmonic generation (HHG) is an extreme nonlinear process in which intense pulses of light drive matter to emit high harmonics of the driving frequency, reaching the extreme ultraviolet and X-ray spectral ranges. So far, HHG has always been generated by intense laser pulses that are well described as a classical electromagnetic field. However, the role of the quantum state of light in non-perturbative interactions of intense light with matter has remained unexplored. Here we show that the defining spectral characteristics of HHG, such as the plateau and cutoff, are sensitive to the quantum state of light. While coherent and Fock light states induce the established HHG cutoff law, thermal and squeezed states substantially surpass it, extending the cutoff compared with a coherent light state of the same intensity. Shaping the quantum state of light thus enables the production of far higher harmonics. We develop the theory of extreme nonlinear optics driven by squeezed light, and more generally by arbitrary quantum states of light, introducing the quantum state of the driving field as a degree of freedom. High-harmonic generation is a source of high-frequency radiation and is typically driven by strong, but classical, laser fields. A theoretical study now shows that using quantum light states as the driver extends the spectrum of outgoing radiation in a controllable manner.

We develop a quantum-optical theory of high harmonic generation under the strong-field approximation, showing that continuum electronic trajectories and the corresponding attosecond pulses (envelope, duration & phase) strongly depend on the driving field’s photon statistics.

A key step in ultrasound image formation is digital beamforming of signals sampled by several transducer elements placed upon an array. High-resolution digital beamforming introduces the demand for sampling rates significantly higher than the signals' Nyquist rate, which greatly increases the volume of data that must be transmitted from the system's front end. In 3-D ultrasound imaging, 2-D transducer arrays rather than 1-D arrays are used, and more scan lines are needed. This implies that the amount of sampled data is vastly increased with respect to 2-D imaging. In this work, we show that a considerable reduction in data rate can be achieved by applying the ideas of Xampling and frequency domain beamforming (FDBF), leading to a sub-Nyquist sampling rate, which uses only a portion of the bandwidth of the ultrasound signals to reconstruct the image. We extend previous work on FDBF for 2-D ultrasound imaging to accommodate the geometry imposed by volumetric scanning and a 2-D grid of transducer elements. High image quality from low-rate samples is demonstrated by simulation of a phantom image composed of several small reflectors. Our technique is then applied to raw data of a heart ventricle phantom obtained by a commercial 3-D ultrasound system. We show that by performing 3-D beamforming in the frequency domain, sub-Nyquist sampling and low processing rate are achievable, while maintaining adequate image quality.

Contemporary sonography is performed by digitally beamforming signals sampled by several transducer elements placed upon an array. High-resolution digital beamforming introduces the demand for a sampling rate significantly higher than the signal's Nyquist rate, which greatly increases the volume of data that must be processed. In 3D ultrasound imaging, 2D transducer arrays rather than 1D arrays are used, and more scan-lines are needed for volumetric imaging. This implies that the amount of sampled data is vastly increased with respect to 2D imaging. In this work we show that a considerable reduction both in sampling rate and processing time can be achieved by applying the ideas of Xampling and frequency domain beamforming, leading to a sub-Nyquist sampling rate. We extend previous work on frequency domain beamforming for 2D ultrasound imaging to the geometry imposed by 3D tissues and a grid of transducer elements. This method uses only a portion of the bandwidth of the ultrasound signals to reconstruct the image. We demonstrate our results by imaging a phantom comprised of fishing wires, and show that by performing 3D beamforming in the frequency domain, a sub-Nyquist sampling rate and a low processing rate are obtained, while keeping adequate image quality.