Materials with large optical anisotropy are sought after for polarization control, nonlinear phase matching, the realization of unconventional surface waves, among other applications in classical and quantum optics. Here, we demonstrate a bulk uniaxial crystal with atomic-scale structural modulations, Sr9/8TiS3, has a record birefringence Δn = 2.1 across a broad transparent window in the mid- to far-infrared. The excess Sr atoms, compared to stoichiometric SrTiS3, introduce additional electrons into TiS6 octahedral blocks to form highly polarizable clouds, which selectively boost the extraordinary refractive index. Structural modulation is a new tool for the engineering of refractive-index and anisotropy of quantum materials.

We will examine several mechanisms for generating single polaritons and entangled polariton pairs, including spontaneous downconversion under far-field illumination, excitation by free and tunneling electrons followed by electron post-selection, and population of complementary polariton modes by spontaneous decay of quantum emitters. Current advances in these approaches will be discussed along with the relative advantages of each of them.

Single photon emitters in 2D and nanoscale materials provide an increasingly promising framework for scalable quantum networking and photonic quantum simulation, but control of the emitter photophysics remains an obstacle to the realization of useful photonic quantum technologies. Here, we use correlative cathodoluminescence, photoluminescence, and atomic force microscopies to probe the effect of nanoscale strain gradients on strain-localized excitons in GaSe. With this understanding in hand, we describe the potential for in situ electron-beam manipulation and optical characterization of emitter photophysics.

In this study, we propose the development of a purely silicon-based photonic enhanced single photon emitter that can be optically or electrically pumped. Its design is based on an introduction of near-infrared (NIR) single photon emitting color centers in silicon photonic resonators and diodes by focused ion beams and high energy ion implantation. Color centers will deterministically be implanted in positions of guided high-Q modes to ensure an efficient optical coupling and to enhance the single photon purity, photon indistinguishability and brightness of the device. Implanted species to be tested in the experiments are C and Si that create various NIR single photon emitting centers in silicon.

Squeezing light into deep sub-wavelength volumes or even into few-nanometer gaps has led to the investigation of interesting phenomena, including strong coupling, quantum plasmonics, nonlinearity enhancement, nonlocality, and molecular junctions. Bowtie nanoantennas, as a common configuration for plasmonic nanocavity, have been extensively studied owing to their great enhancement of the localized field. The enhancement rapidly increases as the tips become sharper and the gap becomes narrower. However, every effort paid to increase the extreme sharpness and nanomete rprecision of less than 10 nm gaps result in the downfall of fabrication throughput, since it relies on the probability of achieving one satisfactory piece out of the many fabricated. Here, an intuitive “fall-to-rise” schemes are proposed and experimentally validated using cascade domino lithography (CDL) and capillary-force-induced collapse lithography(CCL). In this report, we successfully establish a controllable lithography method of making extremely sharp bowtie-shaped plasmonic nanocavity with sub-1nm radius curvature reaching the size of a gold nanocluster as well as a single-digit-nanometer gap between such sharp tips. By controlling falling mechanisms of photoresist mask structures, a facileroute to fabricate sub-10 nm plasmonic nanocavity with high yield is provided. In addition, a proof-of-concep tapplication in surface enhanced Raman spectroscopy (SERS) is demonstrated. The numerically calculated intensity enhancement is over 2.2×10^4 with the confined mode volume below 7.14×10^-6 λ^3, the measured average Raman enhancement factor is of the order of 10^6 with the calculated local Raman enhancement factor over 10^8 promising for single-molecular level sensing applications. Furthermore, such sharp plasmonic nanocavity is used to probe and control localized excitons at room temperature, which offers new strategies for active quantum nano-optical devices.Atomically thin semiconductors, WSe2, are coated on top of plasmonic nanocavity and Au tip for tip-enhanced photo luminescence (TEPL) spectroscopy is added to induce tensile strain in the nanoscale region to create robust localized exciton at the hotspot region. Such an approach provides a systematic way to control localized quantum light.This controlling mechanism of nanostructures falling opens up an unexplored gateway towards conquering the limitations of exploring the realm of plasmonics down to the sub-nanometer regime.

The concept of photonic frequency (ω) - momentum (𝑞) dispersion has been extensively studied in artificial dielectric structures such as photonic crystals and metamaterials. However, the ω−𝑞 dispersion of electrodynamic waves hosted in natural materials at the atomistic level is far less explored. Here, we develop an atomistic nonlocal electrodynamic theory of matter by combining the Maxwell Hamiltonian theory of matter with a quantum theory of atomistic polarization. We apply this theory to silicon and discover the existence of atomistic electrodynamic waves. Atomistic electrodynamic waves have sub-nano-meter effective wavelengths in the picoelectrodynamics regime. Further, we show that the atomistic optical conductivity in silicon is highly anisotropic along different momentum directions due to atomistic electronic correlations. Our findings demonstrate that the natural media host variety of yet to be discovered electromagnetic phases of matter and provide a pathway towards the discovery of rich atomic scale light-matter interaction phenomena.

Diamond has emerged as promising platform for quantum science and technology in virtue of the unique properties of its color centers. The efficient interrogation of such centers optically and electrically remains a fundamental aspect towards quantum applications. We discuss our recent work on the silicon and nitrogen vacancy centers, where both nano-optics and electronics are taken into play. Specifically, we will focus on ultrafast single-photon emission, electroluminescence, nanoscale temperature sensing and vector magnetometry.

Next-generation biological sensors and diagnostic tools require high sensitivity and spatial resolution to be able to identify emergent biological behaviour. Correlating multiple interdependent parameters at the nanoscale could help uncover details of cellular response to external perturbations. Temperature and viscosity are key parameters of interest that relate to cellular energetics and metabolism, morphological changes, cell division and active transport. Cells respond to temperature through viscoadaptation, and a change in viscosity may in turn affect the local temperature profile. Diamond nanocrystals containing nitrogen-vacancy colour centres can harness quantum phenomena to perform a variety of sensing tasks such as measuring temperature, viscosity and external magnetic and electric field, at the nanoscale inside live cells. These quantum sensors can operate without suffering from bleaching and are unaffected by changes in local pH and local refractive index, remaining robust to fluctuations in background fluorescence. In this talk, I will present our latest results on performing nanoscale quantum sensing in living cells for reporting two parameters simultaneously: temperature and rheology. We implement a fast orbital tracking scheme on a quantum sensor formed of a 50-nm diamond nanocrystal containing an ensemble of ~200 nitrogen-vacancy centres. This enables 3D-localization beyond the diffraction limit in a dynamic intracellular environment, opening the door to quantum measurements using highly mobile nanoparticles. We demonstrate the operation of the quantum sensor in a living human cancer cell, extracting simultaneously information about the nanoscale temperature environment, the thermal and stochastic forces acting on the nanodiamond, and properties of its viscoelastic environment.

Temperature is one of the most relevant parameters for the regulation of intracellular processes. Measuring localized subcellular temperature gradients is fundamental for a deeper understanding of cell function, such as the genesis of action potentials, and cell metabolism. In this work I will review our latest progresses in NV-based thermometry ultimately leading to the first localized temperature increase detection in a firing neuronal network with precision under 0.1 K.

The development of fluorescent molecular sensors for imaging voltage changes in biological systems has revolutionized neuroscience over the past decade. However, the poor photostability of molecular voltage sensors limits recording times to a few minutes, posing problems for longitudinal studies of network evolution and disease processes. These limitations have led to the uptake of lower-resolution extracellular recording techniques such as multi-electrode arrays (MEAs) for long term neurological research. Here, we present an alternate platform for sensitive high resolution voltage imaging using fluorescent, charge-sensitive defects in a transparent diamond substrate. We demonstrate how this sensing modality can be used to image sub-millivolt signals over millisecond timescales opening new pathways for 2D and 3D neurological imaging applications.

Neurofilament light chain (NfL) is a promising biomarker for neurological disorders, but conventional detection methods are time-consuming and lack sensitivity. Quantum dots (QDs) have emerged as a promising tool for NfL detection due to their unique optical properties. Recent advances in QD-based assays for NfL detection in bodily fluids are summarized, highlighting the advantages and potential applications of QD-based NfL detection in clinical settings. Overall, QD-based NfL detection represents a promising approach for improving the diagnosis and management of neurological disorders.

Superconducting nanowire single-photon detectors (SNSPDs) are a key building block in photon-based quantum computation and communication. To realize a scalable photonic device, integration of SNSPDs on waveguides is necessary. Hereby, one of the most promising waveguide materials is lithium niobate-on-insulator (LNOI). To find the ideal superconductor growth conditions, in this case NbTiN on LNOI, we created a series of superconducting films, while varying the superconductors stoichiometry. Here, the produced SNSPDs become more sensitive at a higher nitrogen content, while for lower amounts of nitrogen the recovery time is reduced, allowing for a direct correlation of sputter conditions and SNSPD performance.

Today’s noisy intermediate-scale quantum (NISQ) era processors have reached an interesting stage in their development where over 50 qubits are routinely available for us. Traditionally these processors have used the gate-based model of quantum computation, however other useful models including quantum walks and analog approaches can be used. As we want versatility for our processors, we will show how they can be used to implement multi photon quantum walks as well digital-analog models for quantum discrimination. In particular we will introduce a model called quantum neural sensing where one can distinguish different states of matter with the measurement of only one qubit.