This PDF file contains the front matter associated with SPIE Proceedings Volume 12447, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Quantum science and technology are attracting world-wide attention due to the impacts they will have on computing and communications which have no classical counterpart. However, quantum also impacts imaging and sensing. Leaving aside how new detection technologies can sense both single photons and measure their arrival time with pico-second precision, the quantum nature of light enables new types of imaging system, which again have no easy classical implementation. This is brief overview of the historical development of quantum imaging focuses on how the photon pairs created through spontaneous parametric down-conversion lead to unusual imaging systems. Referring to the work from across the global community and some work of my own group we will consider which of these imaging approaches might be considered truly quantum and which might have classical analogies. In all cases I will emphasize those systems which seem to offer practical advantage over traditional approaches giving performance benefits in terms of resolution, signal to noise or wavelength coverage.

The use of Rydberg atoms for radio frequency electric field sensing has emerged as a promising alternative to traditional antenna-based designs that enables all-optical readout. However, the need for atomic vapor cells comprised of dielectric materials can adversely affect the electric field distribution at the probing volume. Here we describe the effects of electric field inhomogeneity on measured optical electromagnetically induced transparency (EIT) spectra. This is accomplished using custom-designed waveguide-embedded atomic vapor cells with stub tuners that allow control of the degree of electric field inhomogeneity within the cell. We describe the resulting broadening of the measured EIT feature and the associated reduction in magnitude, which results in an overall reduced sensitivity of the resulting measurement.

Matter-wave interferometers show great a potential for improving inertial sensing. The absence of drifts recommends them for a variety of applications in geodesy, navigation, or fundamental physics. Atom interferometry offers an interesting perspective for the detection of gravitational waves in the frequency band between eLISA and Advanced LIGO. A key feature to reach the targeted sensitivities for these devices is large momentum transfer. Optical lattices are ideal tools to transfer large number of photon recoils onto atoms for interferometry. We demonstrate twin-lattice atom interferometers with up to 1632 photon recoils at a maximum splitting of 408 photon recoils. To reach these large momentum splittings while maintaining interferometric contrast, we utilize delta-kick collimated Bose-Einstein condensates generated on an atom-chip. Twin-lattice interferometers might open up new perspective for a variety of applications using compact atom interferometer geometries.

We will present our recent work on achieving a high-quality factor (Q) in microresonators operating in the longwave infrared (LWIR) range of 8 to 14 microns.1 Advances in this area have the potential to drive new developments in integrated non-linear optics and chip-based sensing, due to the availability of powerful integrated light sources such as solid-state quantum cascade lasers and strong demand for sensing applications in the LWIR atmospheric transparency window. However, until recently limitations in low-loss materials and fabrication processes have resulted in Q factors that are only several thousand. We will discuss the use of germanium as a high-quality material and heterogeneous fabrication process that produces ultra-smooth surfaces. By coupling the output of a QCL into a partially suspended Ge-on-glass waveguide, we were able to achieve an intrinsic Q of 2.5 ×10⁵. Our results demonstrate the importance and potential of using high-quality native materials for integrated photonics in the LWIR range and portends new sensor topologies.

Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the U.V. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s²S_1/2-5p²P_1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s₂¹S_0-5p¹P₁] cooling transition in neutral strontium clocks at 461 nm and the [5s²s_1/2 – 6p²P_3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.

We present a demonstration of a cold-atom optical-microwave double resonance (DR) Ramsey clock utilising an additively manufactured loop-gap-resonator cavity and grating magneto-optical trap (GMOT). The use of additive manufacturing allows for complex cavity structures, more difficult to produce with traditional machining techniques, while the GMOT architecture significantly simplifies the optical system required to trap and cool the atomic sample. In the current demonstration a single laser is used to trap < 3 × 10^{6 87}Rb atoms, cool them to below 10 µK, optically pump and read-out state populations of the atoms after microwave interrogation. A Ramsey-type interrogation scheme is employed with an empirically evaluated optimum free evolution time of 10 ms, limited by the loss of signal due to atoms falling out of the read-out beam. We demonstrate a short-term stability of < 2×10⁻¹¹τ^−1/2, in reasonable agreement with the predicted short-term stability based on the signal to noise ratio of the measured Ramsey fringes. Excellent field homogeneity of the cavity microwave field is demonstrated though Rabi oscillations, while almost complete optical pumping and good field orientation is evidenced by Zeeman spectroscopy of the ground-state hyperfine energy levels. This work is a novel approach towards more compact and portable cold-atom microwave clocks with significant potential for further miniaturization of the system.

We are investigating a method for identifying materials from a distance, even when they are obscured, using a technique called Quantum Parametric Mode Sorting and single photons detection. By scanning a segment of the material, we are able to capture data on the relationships between the peak count of photons reflected at each position and the location of that reflection. This information allows us to measure the relative reflectance of the material and the texture of its surface, which enables us to achieve a material recognition accuracy of 99%, even maintaining 89.17% when materials are obscured by a lossy and multi-scattering obscurant that causes up to 15.2 round-trip optical depth.

Microfabricated optically-pumped magnetometers (OPMs) are advancing magnetic sensing and imaging for applications in space, defense, geophysics, industrial, and biomedical applications. OPM sensors have been developed in academia and national laboratories over the last 20 years, demonstrating the capabilities of small uncooled magnetometers with performance rivaling those of low-temperature superconductors. Many cross-validation demonstrations enabled the adoption of these novel quantum magnetometers in new applications. Translating this technology into industry poses many new challenges, but also opens the door for faster adoption by putting them into the hands of the users. Two example applications are discussed: microfabricated zero-field OPMs for non-invasive functional brain imaging and microfabricated Mz scalar-vector magnetometers for integration into Cubesats for geomagnetic surveying and monitoring. Both applications pose unique challenges and take advantage of unique features of these quantum sensors.

This article serves as a brief report on the recent affairs in quantum compressive tomography, which is a class of techniques that significantly reduce the physical resources needed to uniquely reconstruct any rank-deficient quantum state, channel or measurement without any assumption about the unknown quantum object (be it the rank, sparsity, eigenbasis, etc.) of a given Hilbert-space dimension.

We experimentally investigate the nonlocal phase modulation of multi-frequency-mode twin beams via a fourwave mixing process. Two separated phase modulators interfere nonlocally to modify the beam correlations, resulting in various covariance matrices.

Quantum frequency conversion, the process of shifting the frequency of an optical quantum state while preserving quantum coherence, can be used to produce non-classical light at otherwise unapproachable wavelengths. We present experimental results based on highly efficient sum-frequency generation (SFG) between a vacuum squeezed state at 1064 nm and a tunable pump source at 850 nm ± 50 nm for the generation of bright squeezed light at 472 nm ± 4 nm. We demonstrate that the SFG process conserves part of the quantum coherence as a 4.2(±0.2) dB 1064 nm vacuum squeezed state is converted to a 1.6(±0.2) dB tunable bright blue squeezed state.

As modern optical and atomic magnetometers achieve unprecedented sensitivity and size, weight, and power (SWaP) characteristics, a variety of applications become increasingly relevant. We will present an overview of some of the commercially available sensors and discuss how they present different advantages, along with what would, in our view, be an "ideal" magnetic sensor, through an industry-led and application-motivated lens.

We analyze the full counting statistics of photons emitted by a Nitrogen Vacancy center (NV) under non-resonant laser excitation and resonant micro-wave (MW) control. This allows to build a phenomenological model which relates the relevant physical parameters with the detected fluorescence. Furthermore, we can investigate the time correlations of the emitted photons and elaborate detection and polarization protocols to optimize the energy and time resources while maximizing the system sensitivity.

NV-based magnetometry in single-crystal diamond grown by chemical vapour deposition (CVD), is now a wellestablished technology with demonstrated applications in DC and AC bulk magnetometry. The approx. 500 µm thick plates normally used offer limited contrast when attempting to measure the magnetic properties of small samples (for example biological samples or minerals) placed in proximity of the diamond magnetic sensor. Such applications would benefit from a few µm high-[NV] layer on a low luminescence substrate in order to collect the signal only from NV centres spatially close to the area of interest, allowing the formation of a magnetic image with increased resolution. It is important to ensure that the strain in the high-[NV] layer is spatially uniform and low in magnitude, to preserve the magnetic resolution and to avoid unusable regions on the magnetic sensor. Established techniques to manage strain during CVD diamond growth are not applicable for the deposition of a few µm of material; normally, the substrate would undergo extensive plasma etching to remove contaminants and polishing damage from the surface of the substrate. This is not possible for thin layers, since the etching would increase the roughness and produce NV layers with non-uniform thickness. Here, we present recent developments to obtain thin, high-[NV] layers on high purity substrates with large areas of low strain, by discussing the substrate preparation and strain characterisation before and after growth.

We describe a technique for the rapid determination of the mass of particles confined in a free-space optical dipole force trap without the need for a vacuum environment (Carlse et al., Phys. Rev. Appl. 14, 024017 (2020)). The trapping light is amplitude modulated causing the particle to be released and subsequently recaptured by the optical dipole force. The drop and restore trajectories are directly imaged using a high-speed CMOS sensor to determine the particle mass. These measurements are corroborated using the position autocorrelation function and the mean-square displacement. We also examine the prospect of extending these techniques to particles trapped in liquids.

The Cold Atom Lab (CAL) is a first of its kind quantum physics science instrument that utilizes the microgravity environment of the International Space Station (ISS) for ultra-cold atom fundamental physics experiments. CAL was installed into the US Destiny Lab of ISS by astronauts in May 2018. The CAL instrument was designed for a 3-year mission life and has limited capability to be serviced or upgraded on orbit. Due to its great success the CAL team was requested to upgrade a specific electronic circuit card that was never intended to be replaced on orbit. As such, the instrument was not designed to accommodate easy access to the circuit cards to enable replacement. Therefore, the CAL team at Jet Propulsion Lab (JPL) formed a collaborative team with experts from Marshall Space Flight Center (MSFC) and Johnson Space Center (JSC) to create a new capability for Augmented Reality (AR) to be utilized on ISS that enabled real time astronaut on orbit guidance for critical activities. For the first time ever during an Intra-Vehicular Activity (IVA) a payload developer on the ground (CAL team) was able to see the real-time astronaut perspective video stream and simultaneously direct the astronaut via voice commands as well as with virtual visual annotations in the astronaut's field of view. This AR capability enabled the complex process of accessing and replacing the circuit card and restoring the full functionality of the CAL instrument.

Since the early 20th century, molecular beam research has led to many advances in physics and chemistry, from precision molecule metrology, over tests of fundamental symmetries, and molecular quantum optics to applied mass spectrometry. All such experiments share a common interest in isolating molecules in high vacuum to eliminate any perturbing environment and to be able to probe the particle’s response to tailored optical, electrical or magnetic fields. Here we propose a scheme to explore the properties of charge-reduced or neutral biopolymers and ways to detect them without the need for post-ionization.

We analyze in details experimental measurements of high frequency laser dynamics and chaos generated by a laser diode subjected to phase-conjugate feedback realized using nonlinear wave mixing in a SPS photorefractive crystal in a CAT configuration. In addition to the typical figure of merit, ie, chaos bandwidth, the corresponding spectral flatness and permutation entropy at delay is analyzed. The experiments reveal that chaos, with a bandwidth up to 30 GHz, a spectral flatness up to 0.75, and a permutation entropy at delay of up to 0.99 can be generated. These optimized performances are observed over a large range of parameters and have not been achieved in the conventional optical feedback configuration. Interestingly, when the pump current is reduced, the chaos bandwidth is also reduced while keeping the spectral flatness and the permutation entropy. Our experimental findings are in qualitative agreement with the presented numerical simulations produced using the Lang-Kobayashi model. Such chaotic laser diodes can be used in chaotic cryptography, high-rate random number generation and optical metrology with the enhancement of lidar resolution.

We discuss recent advances towards matter-wave interference experiments with free beams of metallic and dielectric nanoparticles. They require a brilliant source, an efficient detection scheme and a coherent method to divide the de Broglie waves associated with these clusters: We describe an approach based on a magnetron sputtering source which ejects an intense cluster beam with a wide mass dispersion but a small velocity spread of Δv/v < 10%. The source is universal as it can be used with all conducting and many semiconducting or even insulating materials. Here we focus on metals and dielectrics with a low work function of the bulk and thus a low cluster ionization energy. This allows us to realize photoionization gratings as coherent matter-wave beam splitters and also to realize an efficient ionization detection scheme. These new methods are now combined in an upgraded Talbot-Lau interferometer with three 266 nm depletion gratings. We here describe the experimental boundary conditions and how to realize them in the lab. This next generation of near-field interferometers shall allow us to soon push the limits of matter-wave interference to masses up to 10⁶ amu.

We experimentally propose a technique to demonstrate an optical slow-light system using the two-wave mixing (TWM) process in a photorefractive (PR) crystal at room temperature. This technique uses the refractive index variation that occurs in the PR material at room temperature. In this paper, we show that the time delay and the bandwidth of the transmitted pulses can be easily tuned by varying both laser beam intensities and the widths of the input pulses. In addition, time delays of short light pulses are observed with modest pulse distortions at the output of the PR crystal using a pulsed laser at the nanosecond regime.

A mechanically tuned broadband Kerr frequency comb (KFC) is demonstrated in a Whispering Gallery Modes (WGM) microresonator. Due to their tiny mode volumes (V) and ultra-high Q factor ~ 10⁸, optical WGM microresonators exhibit low threshold power for nonlinear phenomena (scales as V/Q²). Here we focus on the production and mechanical tuning of a 300 nm wide Kerr Frequency Comb (KFC) in silica stretchable microspheres. The ability to tune the KFC source – and hence to lock it to a narrow atomic line – makes it suitable as the basis for a future miniature atomic clock.

Quantum sensors based on cold atoms have enormous potential to unlock new capabilities in GPS-denied navigation, civil engineering, intelligence, and Earth observation. But operating these devices in realistic environments is currently extremely challenging, and for the most part the advantages of choosing a quantum sensor over a conventional alternative are lost in the transition from laboratory to noisy field-based environments. In this work, we demonstrate for the first time in hardware that tailored light pulses, designed and implemented in software using robust control techniques, can substantially mitigate some of the most nefarious effects in a Bragg atom interferometer. We show experimentally that embedding robust control into sensor operation can improve the signal-to-noise ratio of a state-of-the-art Bragg-pulse cold-atom interferometric sensor by a factor of 4× under ideal conditions. In the presence of laser-intensity noise that varies up to 20% from shot-to-shot, commensurate with common platform vibrations, we show experimentally that using the same robust control solutions preserves fringe visibility with minimal degradation while the utility of the primitive Gaussian pulses collapses, delivering an at least 8× improvement in phase-estimation uncertainty compared with primitive pulse schemes. Across all observations, robust control delivers better performance in a noisy environment than the native hardware performance with primitive pulses under approximately ideal conditions. Finally, building on this demonstration we present a validated theoretical concept to extend this performance improvement to compact devices using concatenated sequences of robust pulses designed to enhance the sensor’s scale factor. Time-domain simulations reveal up to 10× performance enhancement in the presence of realistic atomic-cloud effects at 102ℏk momentum separation. These results show for the first time that software-defined quantum sensor operation can deliver useful performance in environmental regimes where primitive operation is impossible, providing a pathway to augment the performance of current and next generation portable cold-atom inertial sensors in real fielded settings.

Research and engineering in the quantum domain involve long chains of activity involving theory development, hypothesis formation, experimentation, device prototyping, device testing, and many more. At each stage multiple paths become possible, and of the paths pursued, the majority will lead nowhere. Our quantum metascience approach provides a strategy which enables all stakeholders to gain an overview of those developments along these tracks, that are relevant to their specific concerns. It provides a controlled vocabulary, built out of terms that are designed to be maximally comprehensible to all groups of stakeholders and across all the sub-fields of the quantum domain. In this paper we 1) introduce our Quantum Science Organization (QSO), a not-for-profit group of quantum science and engineer volunteers and stakeholders and 2) list our QSO Charter, 3) overview our Quantum Ontology project and metascience, 4) consider approaches, including AI machine learning and the wildly investigated ChatGPT from OpenAI, 4) explain why Quantum Ontology is necessary to bridging the communications gap and accelerating progress in quantum science and engineering, 5) contrast ChatGPT to ontology-based AI, demonstrating ChatGPT inadequacies for the tasks at hand, 6) review the history of Quantum Ontology, 7) provide examples of quantum physics knowledge and application areas, and 8) preview the beta version of QSO’s global secure infrastructure for developing and providing quantum knowledge as a service (QKaaS). Five recorded presentations by the QSO are accessible via the Video Index below.

Infleqtion’s cloud-accessible quantum design platform “Albert” enables the development of sensors based on ensembles of Bose-condensed atoms. The hardware is programmed by remote users, including control of dynamically reconfigurable optical fields applied to the atoms. This “painted potential” capability enables development of sensors using a diverse set of tools, including atomtronics, Bragg interferometry, and shaken-lattice interferometry. Albert is putting the power to control quantum matter and design quantum sensors in the hands of users ranging from novice to experienced researchers. We will introduce the Albert cloud platform and explore how users can leverage the system for developing their own sensors.

Digital phase-stepping shearography is a modern precision measurement technique for quantifying microscopic displacement gradients and strains of an object surface by interferometric speckle techniques. The phase map of the displacement derivatives of a stressed object is generated using laser speckles in this technique. As a result, the strains of a deformed object can be directly mapped. Phase-stepping shearography is also very useful in industrial non-destructive testing (NDT). In conventional digital phase stepping shearography, a video camera of limited resolution is used for imaging the laser speckles. The maximum resolution of the video camera is only of the order of 5 Megapixels. This limits the spatial resolution for the generated shearograms and phase maps, and consequently, limits the maximum value of the deformations that can be successfully observed in a given situation. We improved the shearography technique and, in particular, performed advanced shearographic experiments with substantially higher spatial resolution than is now achievable. A 24 megapixel still digital image device (DSLR camera) and a Michelson-type shearing setup with an edgeclamped, center-loaded plate are used in this novel technique. Different phase-stepping algorithms were tested, and all of them produced shearograms satisfactory quality. This effectively increases the useful spatial resolution of phase-stepping shearography by roughly 5 times compared to the conventional method using video-rate cameras, and will also improve spatial resolution in many possible applications.

Modern scanning electron microscopes (SEM) have been an excellent tool to probe nature at the nanoscale. Electron beam inspection, metrology, and lithography are some of the many applications of SEMs in the semiconductor industry, material science, etc. In an SEM, the lens system is used to form a focused scanning electron probe (SEP) which scans the specimen. In this work, we report the developments in reconstruction of the wavefunction of the SEP by performing non-interferometric phase retrieval. Firstly, we have explored phase retrieval of the SEP based on defocus variation. A through-focal image series is taken by moving the specimen (Au-C) across a fixed focal plane. These images are used to reconstruct the SEP intensity distributions which serve as the input for iterative phase retrieval. We observe that the defocus variation does not provide enough information diversity causing the reconstructed phase to stagnate. Therefore, we propose an experimental setup that uses a spiral phase plate to generate an electron vortex illumination and introduce substantial information diversity between two intensity measurements. We have shown by simulation that the phase reconstructed by this technique offers a much more robust solution to the phase retrieval problem. Aberration estimation and correction, and low-dose imaging could be some of the direct applications of knowing the complete wavefunction of the SEP. Our goal is the advancement of scanning electron microscopy as a domain where we can completely characterize the beam wavefunction as it is currently possible for transmission and scanning transmission electron microscopes (TEM and STEM).

Visible light laser and optical systems are the heart of precision applications including quantum computing, atomic clocks and precision metrology. As these systems scale in terms of number of lasers, wavelengths, and optical components, their reliability, weight, size, and power consumption will push the limits of using traditional laboratoryscale lasers and optics. Visible light photonic integration is critical to overcoming these bottlenecks and to enable portable and low cost applications. Solutions must deliver low waveguide losses, low laser phase noise and high stability lasers, and key functions such as modulation and wavelength shifting, in a wafer-scale CMOS foundry compatible platform. In this talk we will cover integration of visible light photonics and key components for atom cooling, trapping and interrogation, in the ultra-low loss silicon nitride (Si3N4) waveguide platform, including ultra-narrow linewidth stabilized lasers, ultra-low loss waveguides, ultra-high Q resonators, modulators, filters, beam emitters and other components. Higher level functional integration will be covered as well as atom cooling demonstrations.

Interfacing cold atoms with nanophotonic waveguides and resonators promises stronger atom-light interactions and leads to new paradigms for quantum optics. Here, we demonstrate coupling single atoms to a nanophotonic whispering-gallery-mode resonator using two different methods. The first one is an optical guiding technique that makes use of diffracted light from a nanophotonic waveguide to direct cold atoms to the evanescent region of the resonator. The second one is an optical conveyor-belt consisting of a moving optical lattice for controlled delivery of trapped atoms. Our demonstration enables new applications with scalable light-matter interface based on cold atoms coupled to nanophotonic circuits.

Optical nanofibers – very thin, tapered optical fibers where the waist diameter is less than the propagating light wavelength – have been shown to be very useful tools for atom-light interactions. Their small size and relative ease of integration into optical fiber-based experimental setups, in addition to their minimal perturbation on magneto-optically trapped cold atoms, have ensured their adoption into cold atom physics. Here, we will discuss some recent applications of optical nanofibers to manipulate, trap, and control cold ⁸⁷Rb atoms in ground or Rydberg states. We will present some recent experimental and theoretical results related to the interactions between the atoms and the optical nanofiber field and introduce some of the limitations observed.

We measure radio frequency electromagnetic wave total scattering cross-sections and internal radio frequency electromagnetic field distributions for several novel types of MEMs atomic vapor cells, optimized for Rydberg atom-based radio frequency electric field sensing. Vapor cells that use metamaterial structures are described. The vapor cells are designed for high radio frequency transmission, uniform internal radio frequency field amplitudes, and low radar scattering cross-section. Experimental scattering data and radio frequency field amplitude maps from functioning vapor cells are presented. The total scattering cross-sections are calibrated to the total scattering cross-sections for a series of steel balls, whose scattering is quantified using Mie scattering theory. We measure across a span of radio frequencies ranging from ~1 GHz – 20 GHz. The work is important for engineering Rydberg atom-based radio frequency electric field sensors for deployment in applications such as test and measurement.

We present new modes of operation in a continuous, 3D-cooled atomic beam interferometer designed for inertial sensing. In these experiments, a moving optical molasses cooling stage provides both three-dimensional cooling and excellent dynamic control over atomic beam velocity. By modulating the atomic beam velocity, we modulate the interferometer scale factor, enabling us to extract the absolute inertial phase over many phase cycles without sacrificing short-term sensitivity. These demonstrations provide a path toward solving the longstanding challenge of limited dynamic range in spatial-domain atom interferometric inertial sensors.

We study a phase estimation protocol based on the distribution of a single squeezed state among an array of Mach-Zehnder interferometers (MZIs). The fundamental component of our scheme is the quantum circuit (QC), a linear network that optimally distributes the squeezing generated at one of its inputs among the d MZIs, where d unknown parameters θ₁, . . . , θ_d are then imprinted and the number of photons at the outputs finally measured. For any given linear combination of the parameters, we can optimize the QC and achieve sub-shot-noise sensitivity. Our parallel strategy, based on the mode-entanglement created by the QC, outperforms the rival and more common sequential strategy, in which the same unknown parameters are estimated independently. It also saturates the ultimate sensitivity bound, the quantum Cramer-Rao bound, in a relevant regime of parameters, thus constituting an optimal estimation method in that regime.

Rydberg atoms are highly excited atoms that have large sensitivities to external fields, lending these atoms extraordinary characteristics for fundamental high-precision spectroscopy as well as for electromagnetic-field sensing applications. Recent results on high-precision spectroscopy with cold Rydberg atoms in modulated optical lattices are presented. The discussed approach can serve as a platform for fundamental-physics studies, which include a model-insensitive measurement of the Rydberg constant and a search for wave-like dark matter. As an example for the utility of Rydberg atoms in field sensing applications, an experiment is presented in which the linear Stark effect of cold Rydberg atoms is employed to measure electric fields in cold ion clouds, demonstrating that Rydberg laser spectroscopy allows electrode-free, non-invasive plasma diagnostics.

To study the effects of atmospheric turbulence on the quality of entanglement of photons propagating from a ground station to a satellite and to verify if coincidence measurements of entangled photons can be used to back out atmospheric turbulence parameters for long-distance propagation or moderate-to-strong turbulence , we built an atmospheric turbulence simulator (ATS) in a laboratory setting. The ATS comprised of two afocal systems with a Lexitek phase wheel and a Meadowlark spatial light modulator representing discrete layers of atmospheric turbulence. The ATS could represent propagation distances on the order of 1km and could theoretically simulate Rytov variances as high as 5.16 and Fried parameters as low as 0.5cm for a 1m telescope. The design parameters, numerical simulations, and experimental setup is detailed in this proceeding.

Quantum and optical technologies are emerging as two major research frontiers that could potentially revolutionize computing, communication, and sensing for modern science and engineering. One common foundation for many emerging quantum and optical technologies are the hermiticity of the underlying Hamiltonians, which govern the phases and dynamics of the physical systems. In recent years, significant theoretical and experimental progress has been made to explore symmetry (e.g., parity-time (PT)) protected non-Hermitian physics, which showcases unique properties such as exceptional points, anomalous topological states, etc. Here we showcase two applications enabled by PT-symmetry non-Hermitian dynamics in both classical and quantum optical regions: 1) topological edge mode lasing protected by a non-Hermitian bulk in the synthetic space; 2) quantum squeezing and sensing using cold atoms with anti-PT symmetry.

Coresonant, but orthogonally polarized, whispering gallery modes can couple to each other via the optical spin-orbit interaction. This cross-polarization coupling (CPC) can result in coupled-mode-induced transparency, attenuation, or Autler-Townes splitting. By fitting observed throughput spectra to a numerical model, the CPC strength can be determined and found to agree with the theory. The throughput response to input amplitude modulation provides an independent method of measuring the CPC strength. Observation and fitting of throughput spectra of both polarizations confirms that CPC is nonreciprocal. Induced transparency and attenuation can be observed even without CPC, by utilizing mode superposition. All these effects will be reviewed.

Coupling of light from a microresonator TE mode to a coresonant TM mode will have a different strength than that of coupling from the TM mode to the TE mode. This coupling nonreciprocity, deriving from the optical spin-orbit interaction, is modeled numerically and confirmed experimentally by observing coupled-mode induced transparency and AutlerTownes splitting. By measuring the throughput spectrum in both polarizations when the input directly excites modes of only one polarization, the coupling strengths in both directions can be determined simultaneously by fitting to the numerical model. Some examples and implications are discussed here.

Collapse models describe the breakdown of the quantum superposition principle when moving from microscopic to macroscopic scales. They are among the possible solutions to the quantum measurement problem and thus describe the emergence of classical mechanics from the quantum one. Testing collapse models is equivalent to test the limits of quantum mechanics. I will provide an overview on how one can test collapse models, and which are the future theoretical and experimental challenges ahead.

Non-equilibrium thermodynamics can provide strong advantages when compared to more standard equilibrium situations. Here, we present a general framework to study its application to concrete problems, which is valid also beyond the assumption of a Gaussian dynamics. We consider two different problems: 1) the dynamics of a levitated nanoparticle undergoing the transition from an harmonic to a double-well potential; 2) the transfer of a quantum state across a double-well potential through classical and quantum protocols. In both cases, we assume that the system undergoes to decoherence and thermalisation. In case 1), we construct a numerical approach to the problem and study the non-equilibrium thermodynamics of the system. In case 2), we introduce a new figure of merit to quantify the efficiency of a state-transfer protocol and apply it to quantum and classical versions of such protocols.

Using a four-wave mixing source of intensity-squeezed light, we perform thermoreflectivity measurement of a wire to determine the wire’s temperature with sub-shot-noise precision.

Using a simple and cost-effective water-jet process, we have overcome silicon etch depth limitations to realize a 6 mm deep atomic vapor cell. We have successfully used this approach to demonstrate a two-chamber geometry by including a 25 mm meandering channel between the alkali pill chamber and main interrogation chamber. Additionally, we have recently used this approach in the fabrication of deep cut silicon cells for cold atom systems. The results will be highlighted, as well as providing an overview of our advancements on mass producible components for cold-atom systems and the amalgamation of this technology towards a fully integrated system.

In interferometry, spectroscopy, and holography, HeNe lasers or semiconductor lasers with external wavelength stabilization have been widely used to achieve the required narrow linewidth at 633 nm. Semiconductor lasers utilizing wavelength selective grating fabricated on semiconductor chip enable the miniaturization of laser systems while also providing numerous advantages such as low energy consumption, reliability and tunability by temperature and injection current. Moreover, DBR gratings reduce the complexity of the laser system compared to external cavity solutions where integration of multiple components is required. DBR gratings on semiconductor surface are fabricated without epitaxial regrowth step that could degrade the performance and lifetime of the device. In addition, low-order surface gratings are providing higher reflectivity than high-order gratings which could lead to a decreased emission linewidth and the output power. To this end, at red emission region low-order gratings require a small pitch, which in combination with the required etching depth for surface gratings leads to high aspect ratio gratings. In this work, Modulight demonstrates the fabrication of high aspect ratio low-order DBR surface gratings to optimize the device performance. DBR gratings are fabricated by electron beam lithography (EBL) method to achieve the required tight pitch patterns. EBL gratings are etched to AlGaAs or AlInP cladding layer using inductively coupled plasma reactive ion etching (ICP-RIE) to produce the desired high aspect ratio structures with smooth vertical side profiles. These two cladding materials are compared based on the etching profiles and device performance.

Accelerometers are key sensors in many fields and applications such as precision metrology, gravimetry measurements, gravitational wave observatories, and navigation where position and attitude need to be determined accurately. A combination of six accelerometers provides all the necessary information to estimate position and orientation of a rigid body and thus serves as an inertial navigation system for autonomous navigation. Fusedsilica based mechanical resonators paired with laser interferometric read-outs enable compact high-accuracy accelerometers. In this talk, we will present a wide-band accelerometer based on a double resonator with two test masses of different sizes in a single frame. One of the resonators has a resonance frequency of about 50 Hz, while the other is optimized for lower frequencies and has a nominal frequency of about 10 Hz. The combination of the two resonators allows for excellent long-term precision while maintaining good measurement bandwidth. We will show the experimental characterization in air and in vacuum of the double-resonator using a heterodyne laser interferometer and a fiber interferometer and its expected performance as an inertial sensor.

Here we report on our recent experimental efforts towards the design, fabrication and characterization of various metasurface structures that would allow spatial and temporal control of photon emission from atomic ensembles, as well as state preparation of solid state and atomic quantum emitters. The emphasis is placed on the development of two distinct categories of structures: (i) Micro- and meso-scale free-space self-polarizing confocal cavities formed by dielectric metasurfaces. (ii) flat hyper-gratings fabricated on the surface of a diamond, which would make the radiation pattern from NV centers in the diamond to be highly directional so that the emitted photons can be collected with high efficiency.

Nonlinear interferometers based on correlated photon pairs allow mid-infrared spectroscopy by measuring only near-infrared photons with a silicon-based detector, which offers higher detectivities than mid-infrared detectors. Here, we use the nonlinear interferometer not only to determine the transmission of a sample but also for spectral analysis – analogue to classical Fourier transform infrared (FTIR) spectrometers. The Quantum FTIR analyzes the absorption of gas mixtures with high spectral resolution over a broad mid-infrared wavelength range. Improved emission rates of the photon pair source yield sensitivities similar to a classical FTIR despite an extremely low light exposure on the sample.

High temporal resolution detection for time-correlated single-photon counting (TCSPC) is critical for a broad range of applications, such as sensing, bio-imaging and quantum information. To harness non-classical advantages, high temporal resolution TCSPC is necessary to capture the unique properties of quantum entanglement, in which the precise time delays between two photons are used to reconstruct the biphoton distribution. However, current state-of-the art, high-resolution TCSPC systems, such as superconducting nanowires, have large footprints and require cryogenic cooling to liquid helium temperatures. They are not well equipped to be conveniently mounted on a satellite or transported within a health care facility. Small footprint, simple, low energy consuming single photon detection systems are therefore needed in order for high temporal resolution TCSPC applications to move beyond the research laboratory. In this direction, we demonstrate a proof-of-concept experiment for improving the temporal resolution of single-photon and biphoton detection schemes that is simple, fiber-based, and readily chip integrable. The principle relies on electrooptic gating of fast single-photon and biphoton signals using a high-speed RF pulse which drives an electro optic intensity modulator. As such, the instrument response function (IRF) of the detection scheme takes on the temporal profile of the electro-optic gate. Experimentally, we improve the IRF of our detection scheme from ~1.54 ns to <100 ps, allowing high resolution detection of ultrafast single photon TCSPC signals as well as to observe nonlocal dispersion cancellation effects in ultrafast biphoton distributions. This technique could allow for practical and simplified access to rapid temporal dynamics at the single photon scale.

We present progress toward measuring nanometer-scale vibrations via a frequency-entangled two-photon interferometer. Unlike classical interference, two-photon – or Hong-Ou-Mandel – interference allows for optical metrology with resilience against imbalanced loss, dispersion, and optical background. However, the resolution of traditional degenerate frequency two-photon interference is limited by the photons’ bandwidths, requiring large bandwidths or long integration times to achieve nanometer-scale resolution. We have implemented a twophoton interferometer utilizing highly non-degenerate frequency-entangled photon pairs at 810 nm and 1550 nm, drastically increasing measurement sensitivity while retaining the advantages of two-photon interference. This enhancement comes via a beat note with frequency proportional to the photon detuning of 177 THz. The resulting measurement saturates the quantum Cram´er-Rao bound, maximizing the information extracted per photon. We have demonstrated a measurement resolution of 2.3 nm with fewer than 18,000 detected photon pairs, orders of magnitude better than previous results. By reflecting one photon from the pair off a target surface, we may use our system to study small-scale vibrations.

Advancements in silicon photonics technology have resulted in significant progress toward tactical-grade chip-scale optical gyroscopes for applications such as inertial navigation for a range of self-driving vehicles. Our first generation of gyro, reported a year ago, was a resonant ring gyro fabricated with an ultra-low-loss silicon-nitride waveguide in a racetrack shape with a perimeter of 37 mm and a finesse of 1270. When the laser frequency was tuned to interrogate the resonance with the lowest backscattering coefficient, and balanced detection was implemented to reduce common noise in the two output signals, the angular random walk (ARW) was measured to be 80 deg/h/√Hz, and the gyro output was dominated by backscattering noise. The second-generation reported here utilizes a longer ring to further reduce backscattering noise. The ring resonator is a circular spiral with 33 turns, a length of 1.2 m, and a finesse of 29. When interrogated with a narrow-linewidth laser like the racetrack gyro, it has a measured ARW of 210 deg/h/√Hz dominated by laser-frequency noise. The ARW is higher than that of the racetrack gyro because the balanced detection was not as effective (13.2 dB of common noise rejection compared to 18 dB in the racetrack gyro). Tests in a vacuum indicate that environmental fluctuations do not contribute to the noise, and that most of the measured drift (3,500 deg/h) has an optical and/or electronic origin. We also report the noise performance of the racetrack gyro interrogated in a Sagnac interferometer probed with broadband light. This configuration was inspired by a recent publication from Shanghai Jiao Tong University that reports a resonant fiber optic gyroscope interrogated with broadband light with a measured ARW that meets tactical-grade requirements. The advantages of this interrogation technique are that it eliminates the need to stabilize the resonator, it reduces the component count, and by making use of incoherent light, it reduces the backscattering noise. The measured ARW of the racetrack gyro interrogated with broadband light was dominated by excess noise at large detected powers, and it was a factor of ~900 larger than the ARW of the same racetrack gyro interrogated with the laser. The reason for this increase in ARW is that the advantage of having a high-finesse resonator is lost when the ring is interrogated with broadband light, and the sensitivity is reduced by a factor of the finesse compared to the same ring resonator interrogated with a laser. This reduction in sensitivity is demonstrated experimentally. Achieving tactical-grade requirements will require returning to a laser interrogation, improving the balanced detection scheme to achieve a noise cancellation of 25 dB or better, and optimizing the laser linewidth to minimize both laser frequency noise and backscattering noise.

In the QuantERA project QURAMAN (Quantum Raman) are we aiming for a combination of breakthroughs and improvements of existing components and already existing setups for building a commercial quantum Raman microscope. By combining the project partners’ expertise and skills in quantum optics, nonlinear optics, Raman spectroscopy and medical device design we will develop the next-generation Raman microscope for bio-imaging with quantum-enhanced sensitivity. The background knowledge and idea behind the QuRAMAN project is described in our recent publications (Optica 7, 470-475 (2020)). Where we have demonstrated that the use of continuous wave (CW) squeezed light can improve the SNR of weak Raman signals. However, to beat the performance of state-of-the-art SRS microscopes by means of squeezed light, one must employ amplitude squeezed picosecond pulses in a strongly focusing configuration (using an objective with a numerical aperture above unity). This will enable the imaging of weak Raman features and will push the Raman technology beyond the state of the art by applying pulsed amplitude squeezed light for signal enhancement.

Modern instruments for imaging biological samples often use high-power lasers or fluorescent dyes that can disturb sensitive processes within living organisms such as plants. Additionally, many interesting plant processes have absorption bands within the near-infrared (NIR), a spectral region hard to efficiently and cost-effectively detect using current camera technology. We present a quantum ghost imaging (QGI) protocol using a proprietary time and space-resolving photon-counting visible camera, NCam, and a highly nondegenerate source of entangled photon pairs. The combination of these two technologies allows for low-noise, high-resolution non-destructive imaging in the NIR, while using a camera sensitive for visible wavelengths.