This PDF file contains the front matter associated with SPIE Proceedings Volume 11700, including the Title Page, Copyright information, and the Table of Contents

Introduction to SPIE Photonics West OPTO conference 11700: Optical and Quantum Sensing and Precision Metrology.

Atom interferometers are quantum mechanical devices sensitive to gravitational and inertial forces, with applications in fundamental physics and inertial sensing in the field. Their performance is currently limited by the interrogation time available to freely falling atoms in Earth’s gravitational field, as well as noise due to mechanical and acoustic vibrations. Our experiment probes gravitational potentials by holding, rather than dropping, atoms. We realize an interrogation time of 20 seconds by suspending the spatially separated atomic wave packets in an optical lattice. This record coherence is enabled by the smooth lattice wave fronts, which are mode-filtered by an optical cavity. This trapped geometry suppresses phase variance due to vibrations by three to four orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. The later part of the talk describes recent progress in characterizing and reducing dephasing of the interferometer. An upgraded optical lattice interferometer experiment is currently being commissioned, with the goal of increased sensitivity to gravity.

We present an analysis of the robustness of existing analytic schemes for the implementation of an atomic fountain interferometer, and develop concepts for improving this robustness through the use of optimal control theory. For an interferometer operating in the Raman regime, we consider an implementation that manipulates the atomic momentum states with a series of Rabi pulses, and analyze how robust the population dynamics are with respect to variations in the effective pulse amplitude seen by the atoms in the atomic clouds, and variations in the initial velocity of the atoms relative to the rest frame. We then show that using rapid adiabatic passage to implement momentum transfer can significantly improve this robustness. Finally, we formulate the most general control conditions for an atomic fountain interferometer and design a functional that can be used for an ensemble optimization over the robustness landscape. We show preliminary results of optimizing the system using Krotov's method, suggesting that optimal control may be able to significantly enhance the robustness of atom interferometers.

The remarkable success of atom coherent manipulation techniques has motivated competitive research and development in precision metrology. Matter-wave inertial sensors – accelerometers, gyrometers, gravimeters – based on these techniques are all at the forefront of their respective measurement classes. Atom inertial sensors provide nowadays about the best accelerometers and gravimeters and allow, for instance, to make the most precise monitoring of gravity or to device precise tests of the weak equivalence principle (WEP). I present here some recent advances in these fields.

M Squared is developing quantum sensors for quantum gravimetry and inertial navigation. Using atom interferometry, each promises performance advantages over their classical counterparts. Each system is designed for use in the challenging operational environment of a moving platform, and incorporates active systems that compensate for the effects of environmental noise. Each sensor is presented along with a performance evaluation in laboratory settings and in field trials. An account is also given on how M Squared laser systems are being used to enable some of the world’s most advanced precision metrology experiments.

We review the concept of matter-wave assisted molecule metrology and present the most recent experiments which exploit the capability of universal matter-wave interferometers to measure forces as small as 10^-26 N via shifts of the interference fringes in the presence of well-controlled fields. This technique allows us to compare, in the same instrument, a variety of electronic and magnetic properties for a large range of atoms and molecules. We exemplify this here with precision measurements of the static polarizability of cesium atoms and the fullerenes C₆₀ and C₇₀ as well as dynamically-induced susceptibilities of tailored tripeptides. We also present measurements of magnetic properties such as the diamagnetic susceptibility of ground-state atoms and aromatic and non-aromatic hydrocarbons.

Point source atom interferometry (PSI) is an atom-optical method that measures one axis of acceleration and two axes of rotation from atom-interferometric fringe images. The number of fringes in an image can be less than or larger than one, depending on the system rotation rate and the atom interferometer's sensitivity setting. Previously used methods for analyzing the fringes, such as parametric fittings, are not suitable for a wide range of rotation rates. We introduce a new experimental method that is effective in either case. Our approach does not require prior knowledge of fringe contrast, orientation, frequency, and phase.

A point source interferometer (PSI) is a device where atoms are split and recombined by applying a temporal sequence of Raman pulses. During the pulse sequence, an initially trapped cloud of cold atoms is released and allowed to expand, behaving approximately as a point source. The PSI can work as a sensitive multi-axes gyroscope that can automatically filter out the signal from accelerations. The phase shift arising from rotations is proportional to the momentum transferred to each atom from the Raman pulses. Therefore, by increasing the momentum transfer, it should be possibly to enhance the sensitivity of the PSI. Here, we investigate the degree of enhancement in sensitivity that could be achieved by augmenting the PSI with large momentum transfer (LMT) employing a sequence of many Raman pulses with alternating directions. Contrary to typical approaches used for describing a PSI, we employ a model under which the motion of the center of mass of each atom is described quantum mechanically. We show how increasing Doppler shifts lead to imperfections, thereby limiting the visibility of the signal fringes, and identify ways to suppress this effect by increasing the effective, two-photon Rabi frequencies of the Raman pulses. Considering the effect of spontaneous emission, we show that for a given value of the one-photon Rabi frequency, there is an optimum value for the number of pulses employed, beyond which the net enhancement in sensitivity begins to decrease. For a one-photon Rabi frequency of 200 MHz, for example, the peak value of the factor of enhancement in sensitivity is ~39, for a momentum transfer that is ~69 times as large as that for a conventional PSI. We also find that this peak value scales as the one-photon Rabi frequency to the power of 4/5.

Compared to light interferometers, the flux in cold-atom interferometers is low and the associated shot noise large. Sensitivities beyond these limitations require the preparation of entangled atoms in different momentum modes. Here, we demonstrate a source of entangled atoms that is compatible with state-of-the-art interferometers. Entanglement is transferred from the spin degree of freedom of a Bose-Einstein condensate to well-separated momentum modes, witnessed by a squeezing parameter of -3.1(8) dB. Entanglement-enhanced atom interferometers open up unprecedented sensitivities for quantum gradiometers or gravitational wave detectors.

We use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between 85Rb and 87Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an Eötvös parameter of [1.6 +/- 1.8 (stat) +/- 3.4 (syst)] x 10^-12, consistent with zero violation of the equivalence principle. With a resolution of up to 1.4 x 10^-11 g per shot, we demonstrate the highest sensitivity to the Eötvös parameter of any laboratory experiment.

Large mass, large splitting and long duration matter wave interferometry in unprecedented regimes is necessary for revealing the quantum nature of gravity in the laboratory, as well as for extreme sensing. In this talk I first explain these two applications along with the domain required, namely, micron sized crystals in superposed states separated by 10 microns. Then we will show how one of two principal sources of noise in the system -- noninertial acceleration noise and gravity gradient noise (Newtonian noise) can be mitigated in such systems, to enable one to create and verify superpositions in the above mentioned scales.

We report the current progress in the development of a compact, deployable cold-atom interferometry sensor platform towards atomic sensors for position, navigation, and time (PNT) applications. A simplified atomic sensor head with diffractive optics, an alignment-free optical package, and photonic-integrated-circuit (PIC) compatible laser architecture [1] are essential for its compactness and deployability. This cold-atom sensor platform can be generally applied to gravimeters, accelerometers, gyroscopes, and clocks, and the sensor platform includes significant engineering efforts in the development of grating-mirror magneto-optical traps (G-MOTs), custom titanium vacuum package with passive pumping, and silicon photonics multi-channel on-chip single sideband modulators.

Atom interferometers in which atoms are delocalized over macroscopic distances can provide excellent sensitivity for gravitational measurements. I will describe progress on the design and construction of a two-meter-tall strontium atomic fountain that aims to leverage such atom interferometers to search for new interactions beyond the standard model via tests of the gravitational inverse square law and to make a new measurement of Newton’s gravitational constant. Moreover, I will discuss progress on MAGIS-100, a 100-meter-tall atom interferometer being built at Fermilab to serve as a prototype gravitational wave detector in the 0.3 – 3 Hz range and to search for ultralight dark matter.

Clocks that are based on atomic and molecular transitions can serve as unparalleled sensors of fundamental phenomena. In particular, a clock based on vibrations in a diatomic molecule is a highly precise sensor of the interatomic force, including possible contributions from new physics. Such a clock is also of metrological interest, since vibrational states in homonuclear molecules have extremely long lifetimes. We present the technique of near-resonant magic-wavelength trapping for strontium dimers, which allows us to reach coherence times exceeding 100 ms for far-separated vibrational state superpositions. The development of the molecular clock is accelerated through state-of-the-art quantum chemistry work.

Optical lattice clocks (OLCs) are now the most stable and accurate timekeepers in the world, with fractional uncertainties equivalent to neither losing nor gaining a second over the entire age of the universe. This unprecedented level of metrological precision offers sensitivity to new physical phenomena, opening the door to exciting and unusual applications. I will give a brief overview of emerging applications of OLCs, including gravitational wave detection, tests of general relativity, and searches for physics beyond the Standard Model. I will discuss the concept and basic operating principles of the multiplexed OLC we have constructed. Finally, I will present recent experimental progress we have made towards measuring the gravitational redshift at the centimeter scale using the multiplexed OLC.

Optical clocks have achieved accuracies better than 1 part in 1018 and are now some of the best measurement devices ever made, significantly surpassing previous-generation microwave clocks in terms of stability. A significant challenge is to transition optical clocks to field environments, which requires the ruggedization and miniaturization of the atomic reference and clock laser along with their supporting lasers and electronics. In this talk, I discuss the use of a stimulated-Brillouin-scattering (SBS) laser based on a compact fiber resonator to run an optical clock, demonstrating a potential portable replacement for the bulk-cavity-stabilized lasers typically used as the stable oscillator in these systems. We achieve a short-term stability of 3.9 x 10-14 in 1 s, outperforming the best microwave clocks. I also discuss our development of integrated photonics and detectors for chip-based ion traps as a pathway towards miniaturizing the clock’s atomic reference through elimination of free-space optics for light delivery and collection.

Optical atomic clocks that operate at frequencies up to 100,000 times higher than their microwave counterparts permit better resolutions and accuracies, while also providing more leeway in environmental control for out of lab applications. Many of the precision applications of these clocks, including relativistic geodesy and tests of fundamental physics rely on the intercomparison of at least two optical clocks. Relative comparisons that include single ion clocks, however, can require close to one month of continuous averaging to achieve measurement instabilities near 1 part in 1018. The long averaging times result from limits imposed on the quantum project noise as a result of signal detection from a single ion, as well as atom probe time limitations due to laser-atom decoherence. In this talk I will describe how the phase coherent properties of an optical frequency comb can be used to enable correlated and synchronous measurement of atomic clocks as a means to improve their relative measurement instability by close to a factor of 10, and nearly 100 times speed up in averaging time over conventional measurement techniques.

We will present a new technique for determining the lifetime of long-lived optically excited states. In particular, we are able to implement cavity-enhanced QND style measurements on two optical transitions in strontium as a way of determining the linewidth of the millihertz linewidth optical transition in strontium. The observation of the direct modification of the transmitted probe light also opens the door to direct frequency comparisons between the probe light and the optical transition frequency, perhaps providing an alternative to Ramsey spectroscopy and enhanced measurement bandwidth.

Quantum engineering using photonic structures offer new capabilities for atom-photon interactions for quantum optics and atomic physics, which could eventually lead to integrated quantum devices. Despite the rapid progress in the variety of structures, coherent excitation of the motional states of atoms in a photonic waveguide using guided modes has yet to be demonstrated. Here, we use the waveguide mode of a hollow-core photonic crystal fibre to manipulate the mechanical Fock states of single atoms in a harmonic potential inside the fibre. We create a large array of Schrödinger cat states, a quintessential feature of quantum physics and a key element in quantum information processing and metrology, of approximately 15000 atoms along the fibre by entangling the electronic state with the coherent harmonic oscillator state of each individual atom. Our results provide a useful step for quantum information and simulation with a wide range of photonic waveguide systems.

If one has access to information about a quantum system both before and after a measurement, the usual remit of Heisenberg uncertainty relation (HUR) does not apply. Here, we theoretically and experimentally demonstrate that, in such a scenario, one can retrodict position and momentum measurements without being limited by HUR. The experiment uses a large ensemble of 10^11 atoms in a macroscopic vapor cell, and the results may be applicable for quantum state estimation and sensing, especially for sensitive magnetometers equally capable of measuring the amplitude and phase of an RF magnetic field both below the standard quantum limit.

In general, the process of spin squeezing is employed for atomic sensors that are essentially free from the effect of spontaneous emission. In the case of an atomic clock based on coherent population trapping, spontaneous emission plays a key role. Specifically, when the clock is realized in the Ramsey configuration employing a pair of pulses separated in time, it is the spontaneous emission process during the first pulse that creates the coherent population trapping, by optically pumping the atoms into the so-called dark state. We show in this talk that it is still possible to apply the process of spin squeezing to enhance the sensitivity of such a clock, by designing carefully the sequence of steps in the protocol. Specifically, we consider the approach of using the maximally entangled Schroedinger Cat states, produced via one axis twist squeezing, to achieve Heisenberg Limited sensitivity, representing an improvement in sensitivity by as much as four orders of magnitude.

Using the platform of a trapped-atom clock on a chip, we have generated spin-squeezed states and observed their time evolution on unprecedented timescales, showing that metrological spin squeezing is preserved for one second. We observe up to 8.1(9) dB of metrological squeezing in a cloud of $2times 10^4$ ultracold alkali atoms by quantum nondemolition (QND) measurement in a fiber Fabry-Perot microcavity. The experiment also reveals a surprising amplification effect in the final cavity measurement of the spin state. It results from a subtle interplay between the cavity coupling and the spin dynamics originating from cold collisions. Spin dynamics such as these are an important factor in real atomic clocks that previous proof-of-principle squeezing experiments had not been able to address. Our results open up encouraging perspectives for squeezing-enhanced atomic clocks in a metrologically relevant stability regime.

Quantum mechanics is grounded on the superposition principle, which is the source both of its tremendous success and technological power, as well as of the problems in understanding it. The reason why superpositions do not propagate from the microscopic to the macroscopic world are unclear. Spontaneous wave function collapse models have been formulated to take into account a progressive breakdown of quantum superpositions when systems are large enough; they do so by modifying the Schrödinger dynamics, and therefore they are empirically testable. Deviations are tiny, and require precision measurements. I will review the most recent tests of such models, spanning from optomechanical to underground experiments. I will conclude by presenting possible future experiments.

How can we address the idea of observers in quantum mechanics? The long-standing Wigner’s friend thought experiment provides a conceptual framework for thinking about this question. It considers the the difficulty of reconciling unitary, evolution of systems and non-unitary state update after a making observations. Following from a recent suggested protocol with two friends that share and entangled state, we prove and investigate, in a photonic experiment, a strong no-go theorem for this Wigner’s friend scenario. Specifically, if quantum mechanics applies at the scale of observers, then there are constraints on the set of assumptions: locality; no-superdeterminism; and absoluteness of observed events. We note that this new theorem places strictly stronger constraints on physical reality than Bell’s theorem.

Photonic tests of multiplicative Bell inequalities and other bounds on nonlocal correlations

The fiber Fabry-Perot microcavities (FFPs) with laser-machined mirrors developed in our group have found many applications in atomic and solid-state cavity QED experiments and beyond. Here we show how laser-machined mirror technology can be leveraged to realize a micro-ring cavity. While maintaining key advantages such as small mode cross-section and high finesse, this novel design replaces the FPP's standing wave with a running-wave field that has no blind spots, and gives access to separated clockwise and anticlockwise modes. These are crucial advantages for applications such as atomic spin squeezing for quantum-enhanced clocks and sensors.

Quantum Sensors have been named one of the top 10 emerging technologies of the year by the World Economic Forum in 2020. This talk will highlight some of the commercial opportunities opened up by quantum sensors based on atomic probe particles. These sensors promise to offer disruptive new capabilities in sensing what is underneath the ground, which parts of the brain are active and detecting small objects in the air. I will present new prototypes and first commercial spin-offs branching out form this exciting area of quantum technologies.

Recently, we optically levitated nanoparticles in vacuum and driven them to rotate up to 300 billion rpm (5 GHz) [J. Ahn, et al. Nature Nanotechnology 15, 89 (2020)]. We demonstrated ultrasensitive torque detection with an optically levitated nanoparticle in vacuum. This system will be promising to study quantum friction and other Casimir effects. We also calculated the vacuum frictional torque on a barium strontium titanate (BST) nanosphere near a BST surface, and found the vacuum friction can be enhanced by several orders with resonant photon tunneling.

During last decades many gas sensing mechanisms, based on different physical or chemical interactions with sensitive materials, have been developed, but the problem of precise analysis of gas mixtures still remains. New sensing mechanism has been suggested that is based on an adiabatically changing electric field interacting with the rotational structure of the molecules with dipole moments. A single low frequency gas detector, that can be used for sensing of gas mixtures with high selectivity, accuracy, and sensitivity, has been theoretically demonstrated. The enhancement of the population difference between corresponding molecular levels and reached the theoretical maximum of absorption have been shown.

Quantum sensing using photons has attracted attention in recent years. In this talk, we report our two recent works on photonic quantum technologies for quantum sensing. First, we report a loss-tolerant quantum absorption measurement using quantum destructive interference in a nonlinear interferometer. Our theoretical results show that our approach surpasses the conventional quantum scheme under photon loss at the detection stage. Second, we report an adaptive quantum state estimation (AQSE) with which we can estimate an unknown quantum state with the smallest uncertainty. We show our experimental demonstrations of AQSE using photons, including a recently realized novel protocol for quantum states changing in time.

In this talk, I will give an overview of work in our group connected to quantum sensing of radio frequency photons and vibrations. In the first part of the talk, I will describe our work extending circuit QED to radio frequencies using a qubit to observe the quantisation of radio-frequency eletromagnetic fields ("radio frequency photonics"), along with cooling of the RF mode and stabilisation of non-classical quantum states of RF light. In the second part of talk, I will introduce recent work in which we have been using microwave "squid cavities" for sensing vibrations and quantised currents at radio frequencies.

The thermal-vapor-cell-based atomic radio frequency electric field (RF E-field) measurement technique has developed rapidly. At present, two types of atom-based electric field sensors: atomic electrometer [Nat. Phys. 8(11), 819-824], and atomic superhet [Nat. Phys. 16, 911–915] have been realized. Here, we discuss the most significant advantage of atomic sensors over traditional sensors: the measurement of E-fields by atomic sensors is non-demolition, while conventional sensors are passive and destructive. QND measurement characteristics of an atomic sensor can well combine with the cavity-enhanced technique; thus, the combined system, e.g., a cavity-enhanced atomic superhet, may achieve a measurement sensitivity beyond the traditional system. This powerful sensor will have important applications in many fields, including cosmology, wireless communication, and remote sensing.

In this presentation, we show the efficacy of neural networks in reducing classical resources required for quantum state estimation. The developed methods achieve near-unity fidelities in reconstructed density matrices, and outperform Stokes reconstruction in a wide variety of scenarios.

As quantum network technology is in the research and development phase, it is essential that robust quantum metrology protocols and procedures based on entanglement distribution be established. To enable that, it will be necessary to develop tools, metrics and measurement methods to characterize quantum network components, both individually, and in their interactions with classical and quantum networks. We present our efforts towards metrology of quantum networks and review a few metrology tools that are already available for quantum component characterization.

Quantum logic enables state preparation, readout and spectroscopy of otherwise difficult-to-study ions. Using the coupled harmonic motion shared between co-trapped ions, information can be transferred from the "spectroscopy" ion to the easily manipulated "logic" ion. With this technique we perform high-resolution terahertz-scale rotational spectroscopy of a single CaH+ molecular ion in pure states by leveraging a Ca+ ion as our logic ion. Entangled states between a CaH+ and a Ca+ have also been demonstrated, making molecular ions possible components of hybrid systems for quantum information processing. Because all our laser operations on the molecule are driving stimulated Raman transitions with high detuning, the technique promises to be generalizable to a wide variety of molecular ion species. Additionally, we study the systematic effects of the trap RF electric field on molecular levels and use it to obtain a measurement of the dipole moment of the charged molecule.

High-dimensional entanglement can give rise to stronger forms of nonlocal correlations compared to qubit systems. Beyond being of fundamental interest, this offers significant advantages for quantum information processing. The problem of certifying these stronger correlations, however, remains an important challenge. Here we theoretically formalise and experimentally demonstrate a notion of genuine high-dimensional quantum steering. We show that high-dimensional entanglement combined with judiciously chosen local measurements can lead to a stronger form of steering, provably impossible to obtain via entanglement in lower dimensions. Exploiting the connection between steering and incompatibility of quantum measurements, we derive two-setting inequalities for certifying the presence of genuine high-dimensional steering. We report the experimental violation of these inequalities using macro-pixel photon-pair entanglement certifying genuine high-dimensional steering in dimensions up to 15.

Thin dielectric membranes patterned with a sub-wavelength period structure can be designed to exhibit remarkable properties, including reflectivity in excess of 99.9%. When fabricated from silicon nitride, they can become superb mechanical resonators as well. In this work, we embed such photonic crystal reflectors in the bandgap of a phononic crystal, to attain ultrahigh mechanical quality factors. These hybrid devices can be incorporated into optical cavities and lasers, and offer unique new opportunities for optomechanical sensing and active-cavity optomechanics.

Magneto-gravitational traps use the repulsion of diamagnetic materials by magnetic fields combined with the Earth's gravity to create a weak trap for micrometer-scale diamagnetic particles. A single particle levitated in this trap oscillates harmonically in three dimensions and its position can be measured optically. We have previously demonstrated feedback cooling of a trapped particle using radiation pressure from a second light source, but the low frequencies of oscillation appear to make quantum behavior unreachable, at least on long time scales. We report on progress towards observing the quantum limit of the motion by optical measurements of the particle position on time scales short compared to the oscillation period of the motion, making the behavior approach that of a free particle. We also show that classical pulsed measurements on larger trapped particles can reach remarkably high precision and demonstrate the performance by using it to measure vibrations of the system.

Quantum optomechanics with acoustic waves is an emerging new area within optomechanics with significant potential to engineer and utilize quantum states at a macroscopic scale. In this talk, a Brillouin optomechanical platform will be discussed that unites several favorable properties including high mechanical frequency (~ 10 GHz), very low optical loss and absorption, and back-scatter operation, thus offering a promising route to circumvent existing experimental challenges. Using this system, we (i) observe Brillouin optomechanical strong coupling between the optical cavity field and these high-frequency mechanical vibrations, which enables optical control at a rate that exceeds the system's decay rates, and (ii) perform heralded single-phonon addition and subtraction to a mechanical thermal state, which has the counterintuitive effect of approximately doubling the mean thermal occupation. Having both capabilities provides a powerful toolkit for quantum control with phonons.

Quantum teleportation, the faithful transfer of an unknown input state onto a remote quantum system, is a key component in long distance quantum communication protocols[1] and distributed quantum computing[2,3]. At the same time high frequency nano-optomechanical systems[4] hold great promise as a node in a future quantum network, operating on-chip at low-loss telecom wavelengths with long mechanical lifetimes. Recent demonstrations include entanglement between two resonators[5], a quantum memory[6] and microwave to optics transduction[7]. However, quantum teleportation of an optical input state onto a long-lived optomechanical memory is an outstanding challenge. Here we present our recent experimental progress towards the implementation of quantum teleportation of a polarization-encoded optical input state onto a pair of nanomechanical resonators. We will present recent results as well as main sources of error and possible improvements and future applications.

Levitated optomechanical systems are promising candidates for future quantum sensors due to their decoupling from the thermal environment. I will present recent results on optical and electric feedback cooling of a nanoparticle levitated in a Paul trap, as well as an approach for the efficient detection of the particle’s position based on self-homodyne; both of these topics can be understood as steps towards the quantum regime.

Levitated mechanical oscillator in high vacuum is supposed to be an ideal system for sensing weak force, and diamagnetic levitated oscillator is recently developed with typical working frequency in 1Hz to 100Hz range, especially, diamagnetic levitation is fully passive and suitable for cryogenic condition operation, we will introduce the realization of cryogenic diamagnetic levitation where ultra-low mechanical dissipation is observed, we also introduce a lens-free detection scheme that can applied to detecting oscillator of sub-millimeter size which can be used for acceleration sensing, we finally give examples of application of diamagnetic levitation to the problem of wave function collapse and dark matter particle.

TBD

Precision spectroscopy is an important tool across a wide array of applications, from communications, timing and navigation, to many emerging quantum technologies. I will talk about our groups work to enable robust operation and integration of spectroscopic techniques for laser stabilization using nanophotonics for light delivery and microfabricated vapor cells for containing atomic references. Our approach is able to span a large wavelength range, from the telecommunications band using on chip second harmonic generation to wavelengths in the blue using vapor cells containing alkaline earth atoms.

In this talk, we will present novel types of chip-scale optical frequency meteorological devices. Specifically, will demonstrate and discuss how Kerr-frequency combs interfaced with atomic vapour, micro-machined atomic diffractive elements and miniaturized ultra-stable optical cavities show a promising path towards ultra-stable and chip-scale optical frequency references.

Atomic sensors—devices that utilize individual atoms as the sensing mechanism—offer enormous prospects for high sensitivity, accuracy and immunity to environmental noise. This is because such sensors leverage quantum mechanical properties of the atom such as internal energy level splittings that do not change with time and are immune to sensor fabrication errors. While some of these sensors are now commercially available, they are still bulky instruments that must be individually assembled by hand and will not be widely disseminated in their current form. In this talk I will discuss a new architecture for quantum sensors based on miniaturized atomic beams, with applications to clocks, gyroscopes and photonic quantum devices.

We present results of the experimental investigations of noise characteristics of the self-referencing optical phase demodulator based on a bulk low-pressure acetylene cell at the wavelength 1530.37nm of P9 acetylene absorption line. The configuration is simple, does not need phase locking, and can be operated with high-etendue waves. While the intensity noise of the utilized semiconductor laser at frequency >250MHz was below the photonic noise, the demodulator resolution (i.e., the minimum detectable phase modulation amplitude) was significantly reduced by an excessive laser phase noise. To reduce the output noise, we propose and analyze different balanced detection configurations that increase the resolution to the standard quantum level.

We present experimental results on polarization ellipse self-rotation (PSR) and polarization hole burning (PHB) in the acetylene-filled hole-core photonic crystal fiber for the P5, P7, and P9 vibrational-rotational Doppler broadened (~500MHz) lines at the gas pressures 0.4-4Torr and W-scale power. The experimental values of PHB and PSR effects are in good agreement between them and with predictions of the developed semi-classic model for the acetylene molecules as the saturable rotating dipoles (gyrators) with random orientations. The maximum experimental PSR value normalized to the gas initial absorbance proved to be significantly lower than that observed in alkali-metal vapors earlier..

The protocol of quantum reading refers to the quantum enhanced retrieval of information from an optical memory, whose generic cell stores a bit of information in two possible lossy channels. In the following we analyze the case of a particular class of optical receiver, based on photon counting measurement, since they can be particularly simple in view of real applications. We show that a quantum advantage is achievable when a transmitter based on two-mode squeezed vacuum (TMSV) states is combined with a photon counting receiver, and we experimentally confirm it. In this paper, after introducing some theoretical background, we focus on the experimental realisation, describing the data collection and the data analysis in detail.

Phase conjugation is an nonlinear effect that results from the four-wave-mixing process. This peculiar effect, in analogy to a mirror, reflects an incident beam in a way that the reflection constitutes the time-reversal of the original beam. By combining the phase conjugate mirror with ordinary mirrors, a special resonator, called phase conjugate resonator (PCR), is constructed. The phase conjugate resonator has been used in a wide range of applications, including phase aberration correction, image transmission, holography, and phase sensing using interferometers. Here, we explore theoretically the properties of phase conjugate mirror by investigating its action upon a variety of quantum states. In addition, we analyze the input-output relations of a phase conjugate resonator. Experimental results are reported that faithfully verify PCR's enhanced stability as compared to normal resonators. Furthermore, we observe a linewidth narrowing effect that is only present in the phase conjugate resonator.

We measured the temporal modes of non-classical light with sub-picosecond resolution by utilizing time-lenses and time-stretch schemes. We obtained the temporal modes by analyzing both the intensity distribution and the phase distribution of spontaneous four-wave mixing process in highly nonlinear fibers. This research may lead to identification and characterization of unknown quantum processes with lower noise than before.

The propagation of quantum field interacting with a single two-level atom has been studied. Using the Gaussian quantum mode functions, we calculate evolution of the quantum state that includes atomic and field variable. We demonstrated the phase and group velocities of the single photon propagation that can be of great importance for long quantum communications. The results can be used for controlling quantum field propagation, and for design of optical elements such as a quantum prism and a quantum lens.

The resolution limit of standard imaging techniques is expressed by the Rayleigh criterion, which states that two point-like sources are difficult to resolve if their transverse separation is smaller that the Rayleigh length. While the criterion is useful in the case of direct detection imaging, other measurement techniques may not be subject to this limitation. Here we consider the use of imaging to estimate the distance between two incoherent point sources. In this framework, the Rayleigh criterion manifests itself through the so-called Rayleigh curse. The latter expresses the fact that the statistical error in the estimation increases for sub-wavelength separation. Here we show that, in the regime of weak signals, a structured measurement obtained by concatenating a linear interferometer with on-off photo-detection is immune to the Rayleigh curse. In this way we clarify the relation between imaging and interferometry, and establish the optimality of linear interferometry for an arbitrary number of incoherent sources.

State-of-the-art microscopes use intense lasers that can severely disturb biological processes, function and viability. This introduces hard limits on performance that only quantum photon correlations can overcome. Here we demonstrate this absolute quantum advantage, achieving signal-to-noise beyond the photodamage-free capacity of conventional microscopy. We achieve this in a coherent Raman microscope, which we use to image molecular bonds within a cell with both quantum-enhanced contrast and sub-wavelength resolution. This allows the observation of nanoscale biological structures that would otherwise not be resolved. Coherent Raman microscopes allow highly selective biomolecular finger-printing in unlabelled specimens, but photodamage is a major roadblock for many applications. By showing that this roadblock can be overcome, our work provides a path towards order-of-magnitude improvements in both sensitivity and imaging speed.

The imaging technique presented here demonstrates the feasibility of a novel approach to allow in-vivo imaging at extreme spectral ranges with enhanced resolution and ~ms acquisition times. This technique is based on the concept of induced coherence, which in a summarized way allows illuminating the sample with the desired light of an extreme spectral range whereas capturing its image on the camera with visible light. This way, high-performance cameras can be exploited for visible light detection while the correlated partner illumination wavelength can be set for optimum interaction with the sample.

The “quantum Radar” seeks to harness quantum entanglement and squeezing to improve the detection of faint targets beyond the best possible classical sensor. The major challenge of the quantum Radar is the very large optical loss of the target beam, which induces vacuum fluctuations and hampers the quantum correlation. In addition, the faint target reflection requires the use of high power beams, which favors high-power stimulated sources of coherent squeezed light over spontaneous low power sources of entangled photons. I will present the lossy SU1,1 nonlinear interferometer with coherent seeding as a candidate for quantum Radar sensing. I will highlight the quantum features of this sensor and report a demonstration of the quantum enhanced interference contrast, even in the presence of high loss.

Recent advances in silicon photonics have enabled large-scale optical phased arrays for applications such as beam steering and directional light detection. However, to date, these results have only been applied to coherent light. Many applications, including passive imaging with natural illumination, require operation using incoherent and/or broadband light. Here we implement an optical phased array designed for these applications using a planar, fractal, pathlength-matching architecture known as an “H-tree”. We demonstrate electronic beamsteering and natural light imaging using this flat, broadband, photonic-integrated device.

Superresolution techniques based on intensity measurements after a spatial mode decomposition can overcome the precision of diffraction-limited direct imaging. We present both the experimental implementation of simultaneous spatial multimode demultiplexing as a distance measurement tool and the theoretical analysis of the actual sensitivity limits given the main experimental imperfection: cross-talks between channels. We demonstrate the distance estimation between two incoherent beams in both directions of the transverse plane, and find a perfect accordance with theoretical predictions, given a proper calibration of the demultiplexer. We show that, even though sensitivity is limited by the cross-talk between channels, we can perform measurements in two dimensions much beyond the Rayleigh limit over a large dynamic range. Combining statistical and analytical tools, we obtain the scaling of the precision limits for weak, generic crosstalk from a device-independent model as a function of the crosstalk probability and N.

A conventional resonant detector is often subject to a trade-off between bandwidth and peak sensitivity. Anomalous dispersion has been shown to improve the bandwidth-sensitivity limit by signal amplification, but its unstable issue in operation needs additional feedback control. Here we propose a stable quantum amplifier enabled by two-mode non-degenerate parametric amplification. As the amplifier operates at threshold, one mode of the amplifier forms a parity-time(PT)-symmetric system with the mode of the original detector, while the other mode of the amplifier collects signal and gets extracted by a readout. Viewed more broadly in the context of coherent quantum control theory, we are attaching a controller that consists of a time reversal of the plant, which, by canceling the inertia of the plant, helps drive up the closed-loop signal gain. Examples of microwave cavity axion detectors and laser-interferometric gravitational-wave detectors will be discussed for this technique.

Quantum control provides a pathway to extract more - and more useful - information from quantum sensors. In this presentation we will highlight a series of experimental and numerical studies demonstrating how quantum control can augment the performance of atomic and solid-state devices for gravimetry, precision navigation, and magnetometry. We begin with demonstrations that a class of cloud-compute-enabled AI agents can be used to autonomously optimize cold-atom loading and BEC production without user intervention. Next, we focus on the application of robust control to mitigate platform noise in fielded atom interferometers. We show 10X improvements interferometer visibility under realistic noise conditions, and also demonstrate up to 1000X improvements in sensitivity under transverse acceleration. Finally, we present novel operating techniques for magnetometry in cluttered environments, in which Slepian window functions are employed to suppress out-of-band sensitivity.

PT-symmetric optical systems can be used for unconventional control and manipulation of light. We designed chirped circular Bragg lasers with radial PT symmetry and analyzed their modal properties. Compared with the conventional circular Bragg lasers, PT-symmetric circular Bragg lasers possess more versatile modal control with further enhanced modal discrimination between the radial modes and between the azimuthal modes. PT-symmetric circular Bragg lasers also have advantages in rotation sensing by exploiting the effects of rotation on modal threshold gain. Their rotation sensitivity can be two orders of magnitude higher than that of conventional circular Bragg lasers with similar geometry and threshold gain. Additionally, they are more robust against perturbation induced by environmental variations than sensors that must operate at the exceptional point.

Operating an optical device at an EP causes small perturbations  applied to the device’s optical path length to produce a greatly enhanced splitting of resonance frequencies due to the splitting being proportional to  at the EP, instead of  as for conventional devices. For increasingly small  , the EP splitting can therefore be larger by several orders of magnitude by operating sufficiently close to the EP. This enhanced splitting has drawn great interest recently, in particular for the potential to miniaturize the optical gyroscope. However, a small but growing number of publications claim that EP sensors may not achieve a proportionally larger signal-to-noise ratio once the full readout system and noise is accounted for. Many different EP sensors have been proposed, some as passive resonators, others as resonators with internal gain operated either below or above lasing threshold. Each sensor class may use a different readout system to measure the splitting and is therefore subject to different noise, but the recent trend has been that once noise and readout system have been accounted for, the enhanced  response cancels out and a signal-to-noise ratio proportional to  is achieved. Despite this cancellation, enhanced precision in EP sensors has still been predicted, although there is disagreement in whether the enhancement arises from the EP or another aspect of the sensor’s architecture, such as the gain. In this paper, we demonstrate through simulations that the EP in two-coupled-mode resonant (below lasing threshold) gyroscopes plays no role in enhancing the signal-to-noise ratio. An all-passive EP gyro is simulated in the limits of shot noise and detector noise to show that in either of these noise limits, no improvement in SNR over the equivalent single-ring gyro is possible. One of the rings is then given gain to show that a large enhancement in detectornoise- limited SNR (~2400 fold) arises, but close proximity to the EP is not necessary to maximize this enhancement; the enhancement is actually significantly larger when the sensor is detuned from the EP. This gain-loss gyro is then compared to a single-ring gyro with gain to show that large sensitivity enhancements are possible in both architectures because the gain compensates the resonator loss, resulting in a narrowing of the resonance linewidth and a greater response to a rotation, but the coupled-ring gyro exhibits a much greater stability to gain fluctuations.

We demonstrate a nuclear magnetic resonance gyroscope based on the 14N nuclear spins intrinsic to nitrogen-vacancy (NV) centers in diamond. Nuclear spins were polarized and readout optically, without the use of microwave transitions [1]. We used double-quantum nuclear Ramsey technique that increases sensitivity to rotations while suppressing the effect of thermal drifts. The device was mounted on a rotation platform and faithfully reported rotation rates in the range of 5-500 mHz. Significant progress can be expected by switching to bulk 13C nuclear spins in the diamond crystal that will be optically polarized via NV centers.

We present a discussion of our new type of dual-species NMR gyro, based on synchronous spin-exchange optical pumping. We present data comparing single-species and dual-species NMR gyros, showing the cancellation of magnetic noise in dual-species NMR gyros.

In this paper, we will present some of our recent work on whispering gallery microsphere and microbubble resonators and their applications in optical sensing, nonlinear optics and frequency comb generation. In particular, we have been working on direct blue frequency comb generation using such devices and our most recent results will be presented. It is hoped that this will show some of the advantages and limitations of WGM resonators coupled to tapered optical fibers for visible light comb generation.

Induced transparency and attenuation are observed in fiber-coupled microresonators due to coupling between coresonant whispering-gallery modes of orthogonal polarizations. Theoretical analysis has shown that this cross-polarization coupling is asymmetric (or nonreciprocal); the coupling from TE to TM generally has a different strength than TM to TE coupling, and the strengths depend on the mode numbers. In an experiment where one polarization is input and the outputs of both polarizations are simultaneously detected by matched detectors, the two coupling strengths are determined by fitting the experimental output spectra to a model. Comparison to theory may then lead to identification of the two modes involved, even when the microresonator dimensions are large compared to the wavelength. Some theoretical results that give similar coupling strengths to those observed in the experiment are presented to give an estimate of typical mode numbers involved.

We describe how photon-phonon interactions can be used to achieve large optical non-reciprocity and ideal optical isolation with integrated photonics. Our experiments rely on breaking time-reversal symmetry within dielectrics (e.g. silica, aluminum nitride, lithium niobate) using the Brillouin scattering nonlinearity. We show how the breaking of time-reversal symmetry can also be used to suppress disorder-induced backscattering in optical resonators.

Optical whispering-gallery mode (WGM) microresonators have been widely used as chemical sensors. In practice, most WGM sensing is based on either mode frequency shift (dispersive) or mode linewidth change (dissipative). However, WGM sensors based on the fractional change in throughput dip depth (dissipative) can offer better sensitivity under certain conditions. Recently it was demonstrated that for WGM dip-depth sensors multimode input can further improve the sensitivity as compared to single-mode input. This enhancement in sensitivity is achieved by using an asymmetric tapered fiber to couple light in and out of the microresonator. In this report, we develop a model which predicts the waist radius of the fabricated asymmetric tapered fiber. The radius predicted by the model is verified by measuring the beat length for the two fiber modes that are excited and couple into a WGM.

We demonstrate a new mechanism, suitable for performing remote earth field measurement using synchronous modulation of two laser fields, which are two-photon resonant with the sodium atom’s hyperfine ground states. This mechanism relies on coherent population trapping (CPT), and thus, called the synchronous CPT scheme. We have measured the magnetic resonances in fluorescence from a sodium cell to demonstrate suitability of this scheme for remote magnetometry. A strong magnetic resonance with its dip corresponding to the Larmor frequency is produced in the presence of a transverse magnetic field. To estimate the optimal duty cycle of light modulation for attaining high performance, we measured the amplitudes and linewidths of the magnetic resonance as a function of the duty cycle, by keeping the peak intensity in CPT fields constant.

We report our investigations on the dependence of magnetic resonance spectrum on the light ellipticity and the polarization angle. A rubidium vapor cell with octade-cyltrichlorosilane (OTS) antirelaxation coating has been used in our experiment to produce narrow linewidth magnetic resonances. We show that excitation using elliptically polarized light can simultaneously produce the alignment and orientation resonances in a Bell-Bloom interaction geometry. We have developed a theoretical model to calculate the resonance spectrum using light with a varying degree of ellipticity. Amplitudes of the alignment and orientation resonances show a strong dependence on the light ellipticity. Our study shows that the duty cycle of light modulation can effectively control the amplitude variations of the alignment and orientation resonances with light ellipticity. We propose that the difference between the alignment and orientation resonance amplitudes can be used for in situ measurement of the light

We experimentally demonstrated a scheme for the magnetic field measurement based on an in-line Michelson interferometer (MI) and magnetic fluid (MF). The tip packaged technology of a Michelson interferometer is proposed. The sensor is composed of microspherical structure, single-mode fiber (SMF), hollow-core fiber (HCF), quartz tube, and MF. Since the refractive index of the MF will be changed with the intensity of the magnetic field, the effective refractive index (ERI) of the cladding can be changed, which leads to correlative moves of the reflection spectrum. The magnetic field sensitivity of -118.7 pm/mT is obtained in the magnetic range from 1.36 to 11.8mT. We present a sensing structure, compared with other sensors, that has the advantages of simple, compact, and easy integration. The proposed sensor is expected to offer significant potential for detecting weak magnetic fields.

In this paper, we describe methods for eliminating residual Doppler shifts and engineering vapor cells for specific applications in Rydberg atom-based electrometry. We have shown that a 3-photon co-linear scheme is able to reduce residual Doppler shifts to the order of magnitude of the Rydberg state decay times. Recently, we have carried out experiments using the approach and shown that sub-residual Doppler shift spectral line shapes can be obtained. We demonstrate spectral bandwidths of 500 kHz using the cesium 42P_3/2 Rydberg state. We have also developed several types of novel vapor cells for Rydberg atom-based electrometry for applications in metrology. We discuss and describe our analysis of one of these vapor cells.

A host of astrophysical and cosmological measurements have established that the majority of matter in the Universe is dark matter. Understanding its nature is of paramount importance to astrophysics, cosmology, and particle physics. A well-motivated possibility is that the dark matter consists of ultralight bosons such as axions, with masses far smaller than 1 eV, in which case they are well-described as a classical field. Due to topology or self-interactions, ultralight bosonic fields can form stable, macroscopic configurations in the form of boson stars or topological defects (domain walls). Even in the absence of topological defects or self-interactions, bosonic dark matter fields exhibit stochastic fluctuations. Furthermore, cataclysmic astrophysical events (like black hole mergers) could produce intense bursts of exotic low-mass fields (ELFs). In any of these scenarios, instead of being bathed in a uniform flux, terrestrial detectors will witness transient events when the exotic bosonic fields pass through Earth. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME): an international collaboration to search for such transient events with a worldwide network of more than a dozen time-synchronized optical atomic magnetometers, with stations in Europe, North America, Asia, the Middle East, and Australia. We will report on our latest results and future directions.

Nitrogen Vacancy (NV) centers in diamond have emerged over the past few years as well-controlled quantum systems, with promising applications ranging from quantum information science to magnetic sensing. In this talk, I will first briefly introduce the NV center system, as well as the experimental methods used for measuring them and controlling their quantum spin dynamics. I will then describe two recent experiments utilizing the magnetic sensing capabilities of NVs. Specifically, we measure the magnetization reorientation induced by chiral molecules adsorbed on the surface of a sample with a thin Cobalt layer, suggesting a persistent effect originating from strong exchange interactions. In addition, we image the spatial structure of magnetization in thin van-der-Waals magnets across the phase transition, providing insights into the dynamics of the magnetic domains across the transition.

MEG based on optically-pumped magnetometry (OP-MEG) operates with miniaturized, wearable insulation, in contrast to massive cryogenic dewars for SQUID-MEG, and allows placement of the sensors close to the scalp. This allows more natural head motion during data recording and localized signal quality comparable to, or surpassing, SQUID-MEG. However no OP-MEG system to date has offered full-head coverage with dense sensor packing, and existing systems - as with SQUID-MEG - require the subject to be sealed in a multilayer, passively-shielded vault in order to suppress ambient magnetic fields. Here we present Kernel Flux, which overcomes these limitations. Kernel Flux uses a collection of alkali vapor sensors in a unique array architecture to directly detect the magnetic fields generated by collective neural activity in the brain, while allowing for comfortable head motion. Each Kernel Flux OP-MEG system was designed from the ground up to work as an integrated system optimized around the user's experience, with relevance to natural home and office contexts.

In this video, I present the latest results obtained with our cavity QED setup where an ensemble of cold atoms is trapped in a fiber-based Fabry-Perot cavity, deep in the strong coupling regime. We have observed cavity protected polaritons in the form of two transmissions peaks of the atoms-cavity system, their linewidth being much narrower than the inhomogeneously-broadened atomic frequency distribution. This effect, which was previously observed in solid-state systems, can be reproduced here with tunable experimental parameters and holds great prospects for preserving coherence in large inhomogeneous quantum systems with possible applications to the field of quantum memories.

Optical frequency combs have revolutionized a wide range of applications, and in recent years a miniature frequency comb or microcomb has been demonstrated using compact (often chip-based) microresonators. These devices use the optical Kerr effect and Kerr-induced parametric gain and four-wavemixing to induce soliton mode locking from a continuous-wave optical pump. An overview of the history and physics of these soliton microcombs will be presented including resonator design for soliton generation. After this, progress on the integration of soliton microcombs with pumping lasers as well as results for several applications under study will be discussed. This includes work towards miniaturization of frequency systems for application to time-standards, optical frequency synthesis, precision spectroscopy, telecommunications, LIDAR, and astronomy.

The unique structure of frequency combs, light sources whose lines are perfectly evenly-spaced, allows for new avenues in the measurement of optical signals. Terahertz quantum cascade laser based combs are attractive options for comb-based sensing, as they have low repetition rates and large powers per comb tooth. We will discuss how computational techniques used in concert with these combs can be used to measure the spectrum of an unknown light source|both phase and amplitude. In particular, we will discuss (a) how frequency combs can be used to recover the spectrum of arbitrary optical signals, even incoherent ones, (b) how Fourier-domain methods can be used to retrieve the phase of arbitrary combs, and (c) how terahertz combs can be used to perform high-speed, high-performance spectroscopy.

Dual-comb spectroscopy of trace chemicals using mid-infrared quantum cascade laser frequency combs: recent advances and field applications

Quantum technologies are nowadays emerging as enabling tools for practical applications, such as quantum sensing, quantum computing and quantum metrology. Lasers play a central role in many of these technological platforms, e.g. for atomic clocks, ion-based or neutral atom-based quantum computers or atom interferometers. Here we present a complete laser system to cool, trap and control strontium atoms in an optical lattice or in tweezer arrays. A sub-Hz linewidth master laser, locked to a high-finesse optical cavity provides the frequency reference for an ultra-low noise comb. The rack-mounted laser system consists of all cooling, repumping, and clock lasers stabilized to the optical frequency comb. Each of the involved laser frequencies can therefore be tuned and mapped in the frequency domain with a high degree of stability. The system is controlled via a software interface, allowing to operate the cold-atom-based physics package autonomously. The system is tailored for the operation of 88Sr or 87Sr optical lattice clocks, or for quantum computing applications, but other sub-Hz lasers could be obtained by phase locking additional clock laser frequencies to the ultra-stable comb, enabling convenient and accurate optical frequency ratio measurements. The laser system architecture and the relevant characterization measurements will be presented, proposing some user-cases such as quantum computing and atom interferometry on strontium atoms. This represents a technological leap for quantum optics, allowing to explore further applications of quantum sensors outside a traditional lab.

Spatiotemporal beams that combine two orbital-angular momenta using a frequency comb

Intracavity Phase Interferometry (IPI) has evolved into a powerful technique for high-precision metrology. In this method a parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. The phase shift becomes a frequency shift applied to the corresponding frequency comb, which is measured by interfering the shifted comb with a reference comb created in the same laser cavity. Although fiber lasers are ideal for implementation of IPI, there are several challenges to achieve a deadband-free fiber IPI sensor. The huge amount of phase coupling between crossing pulses eliminates the small signal response. A successful observation of a beat signal was achieved in a polarization maintaining mode-locked fiber laser operating with orthogonally polarized pulses.

Nitrogen-vacancy centers in diamond have been long used for spin-based optical sensing and also considered viable candidates for implementing quantum information protocols using their spin degree of freedom. Their nanoscale size and the possibility of optical spin readout make them particularly attractive for the use in integrated nanophotonic and quantum optical devices. We will discuss how the optical Purcell effect in plasmonic systems affects the NV spin readout signal and present the demonstration of this readout through optical plasmons in an integrated nanophotonic interface. We will show that spin relaxometry is a powerful tool that allows to probe the magnonic density of states and its electrical tuning with sub-um spatial resolution. Furthermore, we will discuss how spin signal readout sensitivity can be enhanced with the use of plasmonic nanostructures deterministically assembled on the nanoscale.

Diamond optical emitters have been explored extensively in recent years for applications to quantum information and processing. In addition, they have been considered for quantum sensing, especially as nanocrystals in biological systems. Supplementing nanodiamonds with upconversion particles opens new opportunities for biosensing. In this talk I will review the basics of sensing with nanodiamonds and nanophosphors in the context of specific applications. Lastly, I will discuss future opportunities for both types of particles toward virus detection.

This is the presentation of Title Solid-state laser refrigeration of nanodiamond quantum sensors

Real-time temperature monitoring inside living organisms provides a direct measure of their biological activities, such as homeostatic thermoregulation and energy metabolism. Here, using quantum nanothermometers based on optically accessible electron spins of nitrogen vacancy centers in nanodiamonds, we demonstrate in vivo real-time temperature monitoring inside nematode worms. We developed a thermometry system that can measure the temperatures of mobile nanodiamonds inside the worms with a precision of ± 0.22 oC. Using this system, we determined the increase in temperature based on the thermogenic responses of the worms during the chemical stimuli of mitochondrial uncouplers.

Detection signal to noise ratio lies at the heart of any remote sensing task. Matched filters have long been deployed as the optimal devices for radio and microwave receiving. However, their implements in the optics domain are challenging due to a much higher bandwidth and the intensity-only measurement by incoherent detectors. For applications involving high noise and low signal, their utilities are overly restricted by a fundamental trade-off between the signal detection efficiency and noise rejection. In this talk, I will describe a nascent approach, quantum parametric mode sorting, to addressing these practical and fundamental challenges. It is realized via quantum frequency conversion at the phase matching edge, where the signal distillation, picosecond timing tagging, and wavelength transduction are accomplished during a single pass through a nonlinear waveguide or crystal. I will report our experimental progress on using it a variety of single photon sensing and imaging tasks.

This is the presentation of Detecting coronavirus with FASTER CARS: molecular coherence at work

We provide an introductory overview of medical and industrial x-ray imaging applications and requirements for readers whose primary background is in quantum imaging. We discuss some opportunities for quantum X-ray imaging and related techniques such as ghost imaging to provide meaningful benefits in imaging and explain some of the key challenges that remain before practical applications can reach end users.

We propose a Nanodiamond based Biological Physical Unclonable Function for securing in-vivo and in-vitro biosensing devices connected to Internet-of Things healthcare systems for remote patient monitoring . We take advantage of nontoxic biocompatibility and antibacterial activity of nanodiamond films and cavities that can produce strong pseudo-random electromagnetic responses upon electrical or laser triggering due to the fluorescence coming from multiple color centres coupled to such cavities. Such quantum-photonic randomness provides robustness against modelling and side-channel attacks employing machine learning by remote-hackers and can be used to generate a framework of securing biomedical Internet of Things devices and architecture.

Unconventional properties of non-Hermitian systems, such exceptional points, have recently been suggested as a resource for sensing. The impact of noise and utility in quantum regimes, however, remain highly debatable. In this talk, I will introduce a full theoretical framework to analyze the performance of a dispersive quantum non-Hermitian sensor; parts of our result have been included in our recent paper Lau & Clerk, Nat. Comm. 9, 4320 (2018). Our formalism fully accounts for noise effects in both classical and quantum regimes, and also fully treats a realistic and optimal measurement protocol based on coherent driving and homodyne detection. Focusing on two-mode devices, we derive fundamental bounds on the signal-to-noise (SNR) ratio for any such sensor. We use these to demonstrate that enhanced SNR ratio does not necessarily require any proximity to an exceptional point. Furthermore, we show that non-reciprocity is a powerful resource for sensing even when quantum noise exists.

We present methods to enhance the response and reduce the noise in a broad class of ultrafast laser sensors, including but not limited to gyroscopes, accelerators, field sensors, and displacements.. Sensitivity enhancement through “exceptional points” was inspired by quantum mechanics. It is shown that this enhancement comes at the cost of a faster increasing noise. However, we demonstrate enhancement without noise increase in mode-locked lasers where two uncoupled pulses circulate at the same group velocity, without any coupling. Such sensors having reached the classical noise limit, quantum mechanical squeezing methods to further increase the signal to noise will be discussed.

Laser sensors incorporating fast light or exceptional points (EPs) have demonstrated increased scale-factor sensitivity, but have yet to demonstrate a corresponding increase in measurement precision due to excess noise. We find that in the linear regime, EPs are rotationally invariant and so do not boost precision, regardless of the type of EP. This limit also applies above threshold to EP systems that use dissipative coupling, which explains recent experiments in conventional laser gyroscopes that found no increase in precision at the deadband edge. However, above threshold the rotational symmetry of EPs can be broken by gain saturation. We find that EPs in conservatively-coupled systems with a saturation imbalance can lead to an increase in precision.

The minimum possible uncertainty when estimating a parameter, in this case transmission, is bounded by the quantum Cramér-Rao bound (QCRB). This bound is independent of the measurement technique and as result can be used to quantify how close a measurement is to the optimal one for a given system and probing state, as an optimal measurement saturates the QCRB. The ability to perform transmission measurements through an optical system at the QCRB can lead to enhancements in the calibration of optimal states for interferometers, the characterization of high efficiency photodetectors, or the sensitivity of sensing devices based on transmission, such as plasmonic sensors or spectroscopy. We show theoretically that the ultimate sensitivity limit per photon in the estimation of transmission, achievable with Fock states or vacuum two-mode squeezed states (vTMSS), can be approached through the use of bright quantum states of light, such as bright single-mode squeezed states (bSMSS) or bright two-mode squeezed states (bTMSS). The use of bright quantum states has the advantage that they can be generated with a significantly larger number of photons, which leads to an absolute sensitivity that can be many orders of magnitude larger than the one achieved with Fock states or vTMSS. We identify a measurement strategy that saturates the QCRB for these bright quantum states and shown experimentally that transmission estimation at the QCRB can be achieved with bTMSS through optimized intensity difference measurements.

Ordinarily, quantum-measurement based state discrimination methods use Bayesian inference to determine the maximally likely optical input state out of N possible inputs. Each practical single-shot measurement yields a unique vector of N likelihood values (one per each possible outcome) whose significance is not appreciated. Here we show theoretically and experimentally that measured Bayesian likelihood values are equal to observed probabilities of a successful state discrimination. Thus, the vector of Bayesian likelihoods provides significantly more information about the input state than is available in a typical state discrimination measurement.

Nonlinear nanophotonic devices can provide a compelling path for the on-chip generation of coherent visible light, with potential applications in metrology and coherent control of quantum systems. I will discuss how third-order optical parametric oscillation in silicon nitride microresonators, in particular, can enable a wide range of visible wavelengths to be accessed, by realizing systems in which the generated signal and idler fields are widely separated in frequency from the pump. For example, we demonstrate devices pumped at 780 nm (385 THz), in which the visible wavelength signal and near-infrared wavelength idler are separated by more than an octave. Moreover, through geometric control of dispersion, a few THz shift in pump frequency results in a >130 THz shift in the generated signal frequency, enabling visible light at red, orange, yellow, and green wavelengths to be created. I will discuss the conditions needed to realize this widely-separated optical parametric oscillation process while suppressing potential competing nonlinear processes.

The integration of cold neutral atoms with nanophotonic circuits offers significant potential as a light–matter interface for a wide range of applications ranging from fundamental studies in quantum optics, quantum many– body physics, quantum networks to even ultracold chemistry. Here, we describe the design and realization of a novel platform where an efficiently–coupled microring photonic circuit on a chip is integrated with a cold atom system. This platform is fully compatible with laser cooling and trapping atoms, which allows for direct loading of cold atoms in close vicinity of a microring circuit. We discuss our experimental scheme and efforts to prepare for an array of individually trapped atoms within the near field region of a whispering-gallery mode (WGM) in a microring resonator for realizing strong atom–light interactions. Beyond our original motivations in creating an atom-photon quantum interface, we also discuss a novel application – for direct photoassociation (PA) synthesis and quantum state detection of cold diatomic molecules without closed optical transitions. We estimate that the transfer efficiency to a molecular ground state and the subsequent state detection efficiency can approach unity with strong photon–molecule coupling that could be realized in our microring resonator circuit.

Transition metal dichalcogenide semiconductors are ultrathin thin semiconductors that host a rich suite of photophysical phenomena. Excitons govern light-matter interactions in these 2D semiconductors and are fundamental packets of energy that can be manipulated with external stimuli and nanofabricated environments for next-generation technologies. Using nano-optical spectroscopy techniques to access excitonic physics at extreme length scales, a striking diversity of excitonic phenomena has been identified in these 2D materials, including heterogeneity due to edge states and charge puddles. Our latest findings highlight how strain localizes excitons on length scales that are commensurate with their size due to wrinkling phenomena that are unique to 2D materials. These results demonstrate the potential of monolayer semiconductors to be utilized for nanoscale optoelectronic devices with unique functionalities derived from excitonic physics.

In this talk, I will give an overview of our research efforts on developing InP/InAsP nanowire (NW) heterostructure photodetectors for NIR-LWIR detection. I will discuss design, modeling, growth, device processing and optoelectronic properties of both single NW devices and large square millimeter devices comprising millions of NWs connected in parallel. The developed device family includes p-i-n and SAM avalanche diodes, as well as state-of-the-art photoconductors with embedded quantum discs. I will discuss a newly developed model that unravels the high, non-linear optical gain observed in photoconductors that stems from complex carrier dynamics involving multiple traps on the surface of the NWs. I will also briefly introduce our recently initiated efforts on realizing bias-tunable detectors with NW arrays embedded in designed photonic crystals for spectral tuning of optical modes.

Stimulated Brillouin scattering (SBS) processes in optical fibers are driven by two optical field components. In most cases, SBS requires that the two fields are co-polarized. However, the process may also be stimulated by two orthogonally polarized optical waves, even though their combined intensity does not include a beating pattern. The process has been demonstrated before in specialty, nano-structured optical fibers. In this presentation, I describe forward SBS processes in standard single-mode and polarization-maintaining (PM) fibers that are driven by orthogonal optical pump waves. In PM fibers, in particular, the axial wavenumbers of the stimulated acoustic waves are 1,000 times larger than those of standard forward SBS processes. This property leads to inter-polarization coupling of optical probe waves that is non-reciprocal. The results may serve for new concepts of distributed optical fiber sensors, microwave-photonic signal processing, and opto-mechanical isolators.

A refractive index (RI) sensor based on three microspheres array (TMSA) Michelson interferometer (MI) is proposed and experimentally demonstrated. The sensor was composed of a TMSA which introduces higher-order cladding mode and a section of silica fiber which is used to transmit light. Due to the flatness and cleanliness requirements of Michelson’s Fresnel reflector, a special packaging method by microtubule was used to protect the end face. The coupling efficiency between the core and the cladding of MI is proved by the coupled mode theory. The results show that the greater the effective refractive index difference (ERID) between different modes, the greater the coupling coefficient can be obtained, and the TMSA achieves the improvement in the ERID between modes. The interference arm of the sensor is 2.7cm, and the size of the microsphere is less than 230 μm. It is discussed in further detail that the order of the excited cladding mode is closely related to the sensitivity of the RI sensing. The experimental results show that the sensitivity of the RI is -56.121nm/RIU. The characteristics of TMSA make it suitable for operation in a variable environment without cross-sensitivity, which may open up new avenues for local temperature sensing.

Speckle patterns are widely used in imaging techniques such as ghost imaging, dynamic speckle illumination microscopy, structured illumination microscopy, and photoacoustic fluctuation imaging. Recent advances in control of speckle statistical properties has enabled the customization of speckle patterns for specific imaging applications. Here, we design and create special speckle patterns for parallelized nonlinear pattern-illumination microscopy based on fluorescence photo-switching. We present a proof-of-principle experimental demonstration where we obtain a spatial resolution three times higher than the diffraction limit of the illumination optics in our setup. Our work establishes that customized speckles are a potent tool in parallelized super-resolution microscopy.

Here we present a cold atom system, small enough to be handheld, and suitable for use in a cold atom sensor. This has been achieved by developing compact and robust components for laser cooling. Notably integrating a centilitre scale vacuum system and diffractive grating magneto-optical trap optics has been a key step in creating this compact cold atom system. The performance of these components is discussed, including the validation of vacuum by using the cold atoms to measure the vacuum pressure. Future improvements are outlined.

We describe the experimental progress and the challenges of integrating a single photon source based on quantum dots embedded in semiconductor nanowires with a cold-atom experiment in which laser-cooled caesium atoms are loaded and confined inside a hollow-core micro-structured optical fiber. We focus in particular on wavelength conversion of the photons between 895nm and wavelengths suitable for satellite links (~794nm).

We will report on the high-frequency operation of QCDs, ICDs, and QWIPs connected to a monolithic coplanar transmission line without air-bridge. A single-period QCD with more than 0.8 A/W responsivity at 300K paves the way towards sensitive multiheterodyne detection at room-temperature.

Integrated photonics has become valuable to a wide range of applications including data communication, ranging, and inertial and chemical sensing. More recently, integrated photonics has also shown promise as a new means of trapping and probing atoms in atomic clocks. In this manuscript, we discuss how controlling the spatial properties of light emitted from an integrated photonics chip can support the realization of an atomic clock with drastically reduced size, weight, and power consumption. Specifically, atomic clocks require the intersection of three orthogonal beams, each with an area of approximately 16 mm², to trap and probe a cloud of atoms. For good trapping, these beams need to be well collimated and polarized, and to exhibit intensity profiles that are as close to uniform as possible. For beams of these dimensions, this means new techniques need to be employed to control the rate at which light spreads across an integrated photonics chip, as well as the rate at which it diffracts out of the chip itself, all while maintaining good collimation. Existing integrated photonics technologies have been limited in the beam sizes they can generate to the order of several 100’s of microns along either axis of the beam, and the results discussed here represent roughly an order of magnitude improvement in that metric.

Recently, it has been demonstrated that demultiplexing Hermite-Gauss (HG) modes represents the quantum-optimal measurement to estimate the distance between two incoherent sources. However, it remains unclear how to practically combine the information contained into several demultiplexing measurements to reach the ultimate resolution limits. In this contribution, we show how estimators saturating the Cramér-Rao bound for the distance between two thermal point sources can be constructed from an optimised linear combination of intensity measurements in a given number of HG modes, in presence of practical imperfection such as misalignment, crosstalk and detector noise. Moreover, we demonstrate that our strategy saturates the quantum Cramér-Rao bound, in the noiseless case, if sufficiently many modes are measured.

I describe a novel apparatus for measurement of thickness and topography of slabs of materials employing probes with filters using polarization maintaining fibers.

This contribution proposes a new method for THz-wave detection that exploits the sensitivity to external fields of the transitions of accurate molecular ion clocks. A THz electric field, off-resonantly coupled to the HD⁺ energy levels, may be characterized from the comparison between the measurements of the lighshifts induced on a two-photon rovibrational transition probed on cold trapped molecular ions, and the theoretical predictions of the molecular ion theory. A set of six independent lightshift measurements may be converted into the amplitudes and the phases of the Cartesian components of the THz electric field in the laboratory frame.

A new measurement method called current-induced magnetic modulation spectroscopy (CIMMS), which measures the electrical impedance in a contactless manner using a high-frequency current and an induced magnetic field, has been proposed. CIMMS is to apply high-frequency minute current to a living body, measure the induced magnetic field with a magnetic sensor to obtain impedance, and measure changes such as respiration, pulse, and inflammation/collapse of lung fields. CIMMS has many advantages such as be able to measure even with clothes on, however, it cannot be realized without a magnetic sensor with high frequency and high sensitivity. Therefore, we focused on optically pumped atomic magnetometer (OPAM) as magnetic sensor used for CIMMS. OPAM has the potential to achieve ultra-high sensitivity and broadband. However, it requires a large and complicated system such as a strict magnetic shield and vibration isolation. Therefore, we developed that small and movable OPAM system that operates under unshielded condition. We also report that we achieved sensitivity of <7.2pT/Hz1/2 at 35~225kHz by using a phase locked loop

Nitrogen-vacancy (NV) center in diamond is a promising candidate for a highly-sensitive magnetometer with high spatial resolution at room temperature. Conventional magnetometry typically uses scanning confocal microscopic techniques that require long measurement times to achieve a wide observation area and/or high sensitivity. Wide-field imaging techniques using CCD/CMOS camera has the advantage of enabling a wide field of view and rapid acquisition time by simultaneously detecting signals from NV centers in a large number of pixels of the camera. Continuous-wave optically detected magnetic resonance (CW-ODMR) is suitable for wide-field imaging of magnetic field using cameras with slow response time. However, only DC or low-frequency (up to kHz) AC magnetic field can be detected using CW-ODMR techniques. Recently, our group has developed a new measurement protocol using CW-ODMR to detect high-frequency (MHz range) AC magnetic fields using the zero-field splitting of the spin triplet states of NV centers. This technique is compatible with CCD-based imaging techniques. In this study, we implement our CW-ODMR protocol and measure the spatial-distribution of high-frequency AC magnetic fields with a wide-field imaging setup. Using our home-built wide-field imaging setup, a bulk diamond sample was mounted on a microwave antenna and a target AC magnetic field was applied by a copper wire placed on the sample surface. By comparing the CW-ODMR spectra with and without applied field, it is demonstrated that the AC magnetic field can be detected and estimated according to the protocol. Detection was performed both in wide-field view and windows of few pixels while averaging the signal over many pixels enabled rapid measurements.