TAU Nanocenter

While quantum key distribution (QKD) shows much potential as a solution to the looming threat that quantum computers place on today’s encryption protocols, efficient and robust systems that operate in free space are still limited. In this paper, we present a classical light analogy of QKD using spatial modes of light, which can provide a higher bit per photon rate than the more commonly used polarization state encoding.We start by demonstrating the BB84 protocol indoors, where we achieve a secure key rate of 1.55 bits per sifted photon. Then, using our outdoor environment, we propagate the signal outdoors over a distance of up to 90 m, modeling the real-world challenges of QKD in free-space applications and successfully demonstrating BB84 for dimensions 2 and 4.

Plastic contamination presents major environmental threats through its degradation into micro-sized particles that are harmful to a variety of organisms, including plants. Among terrestrial habitats, coastal dunes are likely some of the most plastic-polluted, but very few studies thus far have examined microplastic effects on wild plants native to this habitat. Moreover, current research on microplastics has limited environmental relevancy due to the common use of homogenously shaped un-weathered microplastics in exceeding concentrations. Our research examined the effects of microplastics from biodegradable and non-biodegradable origin, in their pristine (raw) and weathered form, at a concentration of 106 particles per ml, on the native coastal plant Cutandia maritima. We first synthesized engineered microplastics of high environmental relevancy from bulk plastic products. Then, we exposed C. maritima plants to …

The coronavirus disease COVID-19 is primarily transmitted through person-to-person contact, but meteorological conditions may influence its spread and severity. High levels of indoor ozone are known to inactivate the virus, yet the impact of low-level tropospheric ozone remains unclear. We thus hypothesized that tropospheric ozone, influenced by seasonal conditions, may mitigate viral spread. We studied the influence of ozone concentration, temperature, and humidity on the COVID-19 reproduction number in three large Israeli cities during 2020–2021. The effect of these parameters was also analyzed in laboratory experiments on viral inactivation. Field results show that in winter, under low temperature and low humidity, the COVID-19 reproduction number decreases with an increase in ozone concentration. In contrast, in the summer, under high temperature and high humidity, the COVID-19 reproduction …

Agriculture made the shift toward resource reuse years ago, incorporating materials such as treated wastewater and biosolids. Since then, research has documented the widespread presence of contaminants of emerging concern in agricultural systems. Chemicals such as pesticides, pharmaceuticals and poly- and -perfluoroalkyl substances (PFASs); particulate matter such as nanomaterials and microplastics; and biological agents such as antibiotic resistance genes (ARGs) and bacteria (ARB) are inadvertently introduced into arable soils where they can be taken up by crops and introduced to the food-web. Thus, concern about the presence of contaminants in agricultural environments has grown in recent years with evidence emerging linking agricultural exposure and accumulation in crops to ecosystem and human health effects. Our current assessment of risk is siloed by working within disciplines (i.e …

Nanoplastics (NPs) pose emerging risks to both the environment and human health. In this study, we use a zebrafish in vivo model to study─and compare─the physicochemical and toxicological effects of two distinct polystyrene NPs: widely used commercial polymeric nanobeads and nanoscale simulated environmental plastics (SEPs) engineered using a top-down accelerated weathering protocol. Zebrafish embryos and larvae exposed to NPs were assessed for changes in development, growth, locomotor activity, and stress and hypoxic responses. SEP─besides being more environmentally relevant than the commercial nanobeads─significantly delayed hatching and reduced body length (up to 150 μm shorter) compared to the minor effects of the nanobeads at the same concentrations. Moreover, SEPs impaired locomotor activity (40% reduction in distance traveled) and triggered a dose-dependent stress …

Quantum states of light, such as fixed photon number (Fock) states, entangled states, and squeezed states, offer important advantages with respect to classical states of light, such as coherent states and thermal states, in different areas: they enable secure communication and distribution of encryption keys, enable realization of sensors with higher sensitivity and resolution, and are considered candidates for quantum computing and simulation applications. To accommodate these applications, suitable methods for generating the quantum states are needed. Today, the quantum states are often produced by a spontaneous nonlinear process in a standard nonlinear material, followed by a series of optical elements necessary for encoding the desired state on the generated photons. In this review, we consider an alternative approach of structuring the nonlinearity of the crystal so that the desired quantum state will be …

It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence; however, this assumption has constrained our broader understanding of coherence and overlooked the potential role of incoherence in nonlinear interactions. In this work, we study the synthesis of optical spatial coherence in second harmonic generation using quadratic nonlinear photonic crystals. We demonstrate a method where the second harmonic coherence is customized by employing quantitative phase retrieval and a complex square-root filter sequentially on fundamental frequency speckles. As a proof-of-concept, we experimentally show incoherent imaging of a smiley face transitioning from infrared to visible light. Moreover, we apply this method to produce two representative types of structured light beams in second harmonic generation: incoherent vortex and Airy beams. During the nonlinear synthesis of …

The risk of plastic pollution in the environment is extensive, affecting various matrices and organisms, as well as processes and co-transport of other contaminants. To sufficiently address this complex, multi-dimensional challenge, the span of methods and instrumentation to plastic research must be equally diverse. Quartz crystal microbalance with dissipation monitoring (QCM-D) is an acoustic sensing piezoelectric instrument that can offer unique information relating to both the extent and mechanisms of interactions of plastics in the environment. But, thus far, QCM-D has been highly underutilized and misinterpreted to study environmental plastic fate. When considering the wider breadth of plastic studies, QCM-D plastic research will help to complement current life cycle assessments of plastic fate in environmental systems. In this review, the unique applications of QCM-D pertaining to environmentally relevant …

Guiding light forms the backbone of numerous photonic circuits that allow complex, robust, and miniaturized light control. Commonly, guiding is achieved by modifying linear permittivity, resulting in a non-homogenous linear medium. Here, we propose and experimentally realize photonic circuits in a homogenous refractive index medium, where the guiding is driven entirely by nonlinear interaction, enabling dual-wavelength light beam guidance and optical control. This mechanism is analogous to spin current transport in sharp magnetic domain walls, where magnetization texture constitutes a spin-dependent potential. Using narrow custom-poled nonlinear photonic crystals, we guide frequency superposition beams that act as pseudo-spins over more than four Rayleigh lengths. We show that guiding properties depend on the relative phase between participating wavelengths, which can be optically switched on and off with an optical pump. Additionally, using two parallel-poled structures, we experimentally realize a pseudo-spin directional coupler, paving the way for numerous waveguiding hallmarks in a single nonlinear crystal and offering robust control over frequency superposition states of light. Finally, our findings show that it is possible to experimentally emulate complex, precise 2D magnetization domain wall structures, opening avenues for exploration that remain challenging in magnetic materials.

Localization phenomena during transport are typically driven by disordered scalar potentials. Here, we predict a universal pseudospin localization phenomenon induced by a disordered vectorial potential and demonstrate it experimentally in an optical analogue of a classical disordered spin-glass magnetic phase. In our system, a transverse disorder in the second-order nonlinear coupling of a nonlinear photonic crystal causes the idler-signal light beam, representing the pseudospin current, to become localized in the transverse plane. This effect depends strongly on the nonlinear coupling strength, controlled by the optical pump power, revealing its inherently nonlinear and non-perturbative nature. Furthermore, this phenomenon is marked by decaying Rabi oscillations between the idler and signal fields, linked to the disorder properties, suggesting an accompanied longitudinal decoherence effect. Our findings offer deep insights into spin transport in disordered magnetic textures and open avenues for exploring complex magnetic phases and phase transitions using nonlinear optics.

Guiding light forms the backbone of numerous photonic circuits that allow complex, robust, and miniaturized light control. Commonly, guiding is achieved by modifying linear permittivity, resulting in a non-homogenous linear medium. Here, we propose and experimentally realize photonic circuits in a homogenous refractive index medium, where the guiding is driven entirely by nonlinear interaction, enabling dual-wavelength light beam guidance and optical control. This mechanism is analogous to spin current transport in sharp magnetic domain walls, where magnetization texture constitutes a spin-dependent potential. Using narrow custom-poled nonlinear photonic crystals, we guide frequency superposition beams that act as pseudo-spins over more than four Rayleigh lengths. We show that guiding properties depend on the relative phase between participating wavelengths, which can be optically switched on and off with an optical pump. Additionally, using two parallel-poled structures, we experimentally realize a pseudo-spin directional coupler, paving the way for numerous waveguiding hallmarks in a single nonlinear crystal and offering robust control over frequency superposition states of light. Finally, our findings show that it is possible to experimentally emulate complex, precise 2D magnetization domain wall structures, opening avenues for exploration that remain challenging in magnetic materials.

In this perspective article, we discuss the analogy between spin transport in magnetization texture and the nonlinear process of sum frequency generation, where the signal and idler complex amplitudes represent the two-dimensional spinor, while the nonlinear coupling represents the material magnetization. This analogy unveils new nonlinear optical effects in both spatial and temporal domains, including the analog of the famous Stern–Gerlach effect, the topological Hall effect in magnetic skyrmion structures, and the transverse localization of spin currents in a disordered magnetic spin-glass phase. Moreover, it enables us to realize new all-optical devices that manipulate superposition states of the signal and idler. Examples include a pump-controlled spin valve, which can either reflect or transmit the signal-idler waves when they are in-phase, and a spin waveguide that guides only in-phase signal-idler waves.

Localization phenomena during transport are typically driven by disordered scalar potentials. Here, we predict a universal pseudospin localization phenomenon induced by a disordered vectorial potential and demonstrate it experimentally in an optical analogue of a classical disordered spin-glass magnetic phase. In our system, a transverse disorder in the second-order nonlinear coupling of a nonlinear photonic crystal causes the idler-signal light beam, representing the pseudospin current, to become localized in the transverse plane. This effect depends strongly on the nonlinear coupling strength, controlled by the optical pump power, revealing its inherently nonlinear and non-perturbative nature. Furthermore, this phenomenon is marked by decaying Rabi oscillations between the idler and signal fields, linked to the disorder properties, suggesting an accompanied longitudinal decoherence effect. Our findings offer deep insights into spin transport in disordered magnetic textures and open avenues for exploring complex magnetic phases and phase transitions using nonlinear optics.

Nanoparticles with diverse characteristics are difficult to quantify at low concentrations in the water environment (106–109 particles mL−1 for nanoplastics originating from the breakdown of plastic debris) for the evaluation of effective treatment methods. This study examines the sensitivity, or limit of detection (LOD), of laser‐induced breakdown detection (LIBD) for the counting of nanoparticles, including nanoplastics. For polystyrene (PS) standards with sizes of 20−400 nm, LIBD shows relatively low LODs (for example, 2 × 106 particles mL−1 for 100 nm particles) compared with turbidity monitoring, UV–vis spectroscopy (both 6 × 108 particles mL−1), and nanoparticle tracking analysis (2 × 107 particles mL−1). For nanoplastics (PS, polypropylene, and polyethylene terephthalate), the detection limits are 104 − 105 particles mL−1, one to two orders of magnitude lower than the PS standards. LIBD can quantify …

We demonstrated experimentally direct femtosecond writing of ferroelectric domains in lithium niobate on insulator. The fabricated ferroelectric domain structures were characterized using Cherenkov second harmonic microscopy and piezoresponse force microscopy. We also experimentally explored the far-field second harmonic generation from the laser-induced ferroelectric domain structures. This study opens the door for direct laser writing of lithium niobate-based integrated photonic circuits, which typically require on-chip frequency conversion and wavefront control.

Control over the joint spectral amplitude of a photon pair has proved highly desirable for many quantum applications, since it contains the spectral quantum correlations, and has crucial effects on the indistinguishability of photons, as well as promising emerging applications involving complex quantum functions and frequency encoding of qudits. Until today, this has been achieved by engineering a single degree of freedom, either by custom poling nonlinear crystal or by shaping the pump pulse. We present a combined approach where two degrees of freedom, the phase-matching function, and the pump spectrum, are controlled. This approach enables the two-dimensional control of the joint spectral amplitude, generating a variety of spectrally encoded quantum states - including frequency uncorrelated states, frequency-bin Bell states, and biphoton qudit states. In addition, the joint spectral amplitude is controlled by photon bunching and anti-bunching, reflecting the symmetry of the phase-matching function.

Plastic pollution, a widespread environmental challenge, significantly impacts marine ecosystems. The degradation of plastic under environmental conditions results in the generation of microplastic (MP; <5 mm) fragments, frequently ingested by marine life, including filter-feeders such as ascidians (Chordata, Ascidiacea). These organisms are integral to benthic-pelagic coupling, transporting MP from the water column through marine food web.Here, we explored the effect of filtration and digestion by the solitary ascidian Styela plicata on the composition of MP in the water column and on the sinking rates of faecal matter, focusing on differences between two distinct plastics, polystyrene (PS) and the biodegradable polylactic acid (PLA). The ascidians efficiently removed 2–5 μm particles within 2 h of filtration. Following digestion and secretion process, PS concentrations in water increased while PLA concentration …

We demonstrated experimentally direct femtosecond writing of ferroelectric domains in lithium niobate on insulator. The fabricated ferroelectric domain structures were characterized using Cherenkov second harmonic microscopy and piezoresponse force microscopy. We also experimentally explored the far-field second harmonic generation from the laser-induced ferroelectric domain structures. This study opens the door for direct laser writing of lithium niobate-based integrated photonic circuits, which typically require on-chip frequency conversion and wavefront control.

In spontaneous parametric down-conversion, the spectral correlations between the signal and the idler are expressed by the joint spectral amplitude (JSA) function. However, in the standard coincidence measurements, the phase information of the JSA is lost, and only the square of the absolute value of the JSA is recorded, thus preventing full characterization of the biphoton state. Here, we present an experimental technique to investigate the interference of biphoton joint spectral amplitudes, unlocking new avenues in quantum photonics research. Our method explores phase-dependent phenomena within entangled biphoton spectra. This is achieved by simultaneously pumping two structured nonlinear photonic crystals and observing their interference, which reveals previously inaccessible effects with direct intensity measurements. We demonstrate the versatility of our technique by analyzing two types of joint …

In spontaneous parametric down-conversion, the spectral correlations between the signal and the idler are expressed by the joint spectral amplitude (JSA) function. However, in the standard coincidence measurements, the phase information of the JSA is lost, and only the square of the absolute value of the JSA is recorded, thus preventing full characterization of the biphoton state. Here, we present an experimental technique to investigate the interference of biphoton joint spectral amplitudes, unlocking new avenues in quantum photonics research. Our method explores phase-dependent phenomena within entangled biphoton spectra. This is achieved by simultaneously pumping two structured nonlinear photonic crystals and observing their interference, which reveals previously inaccessible effects with direct intensity measurements. We demonstrate the versatility of our technique by analyzing two types of joint …

Quantum metrology leverages quantum correlations for enhanced parameter estimation. Recently, structured light enabled increased resolution and sensitivity in quantum metrology systems. However, lossy and complex setups impacting photon flux hinder true quantum advantage while using high dimensional structured light. We introduce a straightforward mechanical rotation quantum sensing mechanism, employing high-dimensional structured light and use it with a high-flux (45 000 coincidence counts per second) N00N state source with N= 2. The system utilizes two opposite spiral phase plates with topological charge of up to ℓ= 16 that converts mechanical rotation into wavefront phase shifts and exhibit a 16-fold enhanced super-resolution and 25-fold enhanced sensitivity between different topological charges, while retaining the acquisition times, and with negligible change in coincidence count. Furthermore …