The interplay between quantum mechanics and gravity is almost as mysterious today as it was half a century ago despite remarkable progress in either field. Putting aside exotic topics like quantum theories of gravity, even a purely classical quantity, such as Newton’s gravitational constant (or “big G”), has not been measured to a precision and accuracy close to that of other fundamental constants (e.g. speed of light, fine structure constant, etc.). Moreover, until recently [1], most measurements of big G have been classical in nature. Therefore, using a quantum sensor, such as an atomic gradiometer, to perform precision measurements of big G not only adds another (quantum) dimension to said measurement, but also opens a window into studying other fundamental classical gravitational phenomena, like measuring gravitational waves [2]. Furthermore, due to the quantum nature of the sensor apparatus, the interplay of gravity and quantum mechanics can be explored by studying effects such as gravitational decoherence [3]. In this talk, I will discuss ongoing progress on the construction of a 2 meter tall atom interferometer using Strontium. By virtue of the bosonic isotope (Strontium-88) having a zero nuclear spin, the demands on magnetic shielding of the apparatus are relaxed compared to (say) alkali atoms. Once operational over the 2 meter baseline, this atom interferometer will be used to perform short-distance tests (10 centimeters to 1 meter) of gravity using source (or proof) masses in the 100 kilogram range or higher. The distance between the gravitational sensor (i.e. atom interferometer) and the proof masses can be varied using appropriate translation stages. This measurement configuration will allow us to perform precision measurements of big G. [1] Rosi et al. (2014). Nature 510, 518-521. [2] Abe et al. (2021) Quantum Science and Technology 6, 044003. [3] Roura (2020). Physical Review X 10, 021014.

In this talk, we will discuss our latest experimental results of a compact, portable cold Cs atom interferometer. The portability of the atomic physics package makes it suitable for implementing atom interferometry with various interrogation configurations and relative orientations. In addition, we will also briefly report the progress on experiments of Cs Rydberg atoms for RF E-field sensing. Our work is aimed at investigating the engineering and atomic physics limitations to the devices’ size, weight and power consumption (SWaP) and reliability.

The Atom Interferometry Observatory Network (AION) is a collaboration of seven UK institutions working on interferometry with strontium atoms. Development work on high-flux atom sources, transport and cooling of atoms, composite pulse sequences and narrow-bandwidth laser systems will be conducted in a coordinated parallel program in five dedicated laser laboratories and tested in table-top apparatus. After testing, the aim is for these sub-systems to be integrated together in a 10 m tall atom interferometer at the chosen site. The AION collaboration is linked to the MAGIS-100 strontium interferometer project in the US (contributing to the interferometry detection and readout platform, including cameras and analysis). A long-term objective is to set up a network of large-baseline atom interferometers with capability of making sensitive searches for ultralight dark matter and gravitational wave detection (with future generations of instruments). Within AION, the team at KCL investigates the applications to fundamental theoretical physics. AION is funded by the Quantum Sensors for Fundamental Physics programme of the UK Research & Innovation (STFC & EPSRC), starting in 2021. The institutions are: Imperial College and Kings College, London; Universities of Birmingham, Cambridge, Liverpool, Oxford; and the Rutherford Appleton Lab.

Atom interferometry for practical and fundamental applications was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Atom interferometers with their extremely high sensitivity to inertial forces are an excellent method for investigating and understanding gravity and its gradients. Studying gravity using quantum mechanical test sources, such as ultra-cold atoms, is an exciting choice for probing physics at this intersection. Here work is presented towards the realization of novel atom interferometers based upon Cd and Sr atoms, which posses a common electronic structure with two valence electrons, also providing access to narrow linewidth intercombination transitions. For these experiments, a novel, high-power, tunable, narrow-linewidth VECSEL source has been developed, which acts as a master source to produce continuous light at either 461 nm or 229 nm, corresponding to the cooling transitions in Sr and Cd atoms, respectively. The laser systems for accessing the clock transition and also the inter-combination transition have also been implemented. The current design of the vacuuum chamber is presented, which involves the transfer of the prepared ultracold atomic clouds from preparatory chambers to a science chamber. Towards this, we have also simulated the generation of a cold atomic source of Cd, which is a key component in producing a high sensitivity atom interferometer.

The wave-particle duality is a key concept of quantum physics and extending quantum superpositions to bodies of increasing mass and complexity has become a key goal to numerous research groups. Such experiments are motivated by the desire to probe and better understand the quantum-classical interface in advanced tests of spontaneous or gravity-induced wave function collapse and in the search for non-linear modifications of quantum theory. High mass interferometry has been proposed to serve in the search for light dark matter via weak recoil decoherence as well as in tests of the weak equivalence principle by comparing a large variety of quantum systems with very distinct internal composition, excitation, mass, shape or angular momentum. Here we discuss the experimental state of the art in high-mass matter-wave interferometry, as well as new perspectives from cluster and nanoparticle physics to push quantum superpositions by 3 to 4 orders of magnitude in mass or up to 6 orders of magnitude in 'macroscopicity'. We discuss different near-field interferometer configurations that shall become useful in near-future demonstrations of quantum phenomena with objects as diverse as proteins, metal clusters and dielectric nanoparticles.

This video was recorded for Photonics West 2022

This video was recorded for SPIE Photonics West 2022

Laser noise usually limits the stability of optical frequency ratio measurements, limiting the speed and precision one can compare two atomic frequency standards. In this talk I will describe two methods, correlation and differential spectroscopy, which utilize correlations in laser noise to increase the achievable interrogation time and thus increase the frequency comparison stability. Correlation spectroscopy is a technique which uses a parity measurement following a synchronized Ramsey interrogation to measure the relative frequency of two similar frequency atomic clocks. With this technique we achieve a measurement instability of (4×10^(-16))⁄√(τ⁄s) for a comparison of two single 27Al+ ion clocks. Differential spectroscopy uses an atomic clock with low projection noise, here a 171Yb lattice clock, to correct the phase noise of a second, higher frequency clock’s local oscillator thereby reducing the measurement instability to the level of the first. This can be further extended using two lattice clocks in a zero dead time configuration to correct the phase noise beyond the interrogation time reachable for a single Yb lattice clock. With these techniques we achieve measurement stabilities of (2.5×10^(-16))⁄√(τ⁄s) and (2×10^(-16))⁄√(τ⁄s) for a comparison between a single 27Al+ ion clock and a 171Yb lattice clock running as single clock and in a zero dead time configuration respectively. In addition to these techniques, I will also discuss recent progress towards characterizing the systematics of the NIST 40Ca+/27Al+ optical atomic clock.

Expanding the toolbox available for the control of individual atoms or ions to single molecules has many promising applications. Using quantum-logic spectroscopy, our group has demonstrated preparation, coherent manipulation, and nondestructive detection of rotational states of CaH+ molecular ions, as well as entangled states relevant for quantum information processing. We are currently building a new cryogenic experimental setup which features a molecular beam with interchangeable gas sources to overcome limitations in the existing experimental setup. With this setup, we plan to improve control over small molecules such as CaH+ and explore quantum state control of larger molecules.

A radium ion optical clock was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Optical haloscope: recent results was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Mechanical sensors for exploring the dark sector was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Optomechanical searches for dark matter was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Recently it has been proposed to search for dark matter using mechanical sensors, exploiting the fact that all dark matter candidates couple to the size or position of atoms. While focus has been directed towards analyzing signal from gravitational wave detectors and equivalence principle tests, a unique opportunity has emerged to develop compact detectors based on cavity optomechanical systems, which have recently achieved force measurements at the quantum limit. I'll discuss this concept from a practical perspective, highlighting a proposal to search for vector dark matter (dark photons) with optomechanical accelerometers. In this context, our lab is developing a new generation of ultra-sensitive accelerometers based on centimeter-scale silicon nitride membranes.

A generalized echo squeezing protocol with near Heisenberg limited sensitivity over a large range of values of the squeezing parameter was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

We revisit the dissipative approach to producing and stabilizing spin-squeezed states of an ensemble of N two-level systems, providing a detailed analysis of two surprising yet generic features of such protocols. The first is a macroscopic sensitivity of the steady state to whether N is even or odd. We discuss how this effect can be avoided (if the goal is parity-insensitive squeezing), or could be exploited as a new kind of sensing modality to detect the addition or removal of a single spin. The second effect is an anomalous emergent long timescale and a "prethermalized" regime that occurs for even weak single-spin dephasing. We also discuss a general hybrid-systems approach for implementing dissipative spin squeezing that does not require squeezed input light or complex multi-level atoms, but instead makes use of bosonic reservoir-engineering ideas. Our protocol is compatible with a variety of platforms, including trapped ions, NV defect spins coupled to diamond optomechanical crystals, and spin ensembles coupled to superconducting microwave circuits.

This video was recorded for SPIE Photonics West 2022

The Heisenberg limit of quantum measurement where the measurement precision scales as N-1 with the number of atoms N can be achieved by introducing quantum correlations between the atoms. In the present work, we show how to reach Heisenberg scaling by implementing a new Ramsey measurement scheme for cold-atom metrological devices. The proposed protocol consists of a sequence of one-axis twisting pulses and total collective spin rotations. It results in the creation of atomic Schrödinger-cat states, a superposition of two coherent spin states. Analyzing the Fisher information, we discuss the main features of the states and their interferometric precision.

We use bright squeezed light to demonstrate that direct absorption and gain measurements can be performed with sensitivity beyond the shot-noise limit without requiring homodyne/lock-in, or logic coincidence detection schemes. Previously we reported more than 1 dB quantum advantage [ 3 dB when corrected losses in optical paths] for the measurement sensitivity at faint absorption levels. We present our detailed results on definite quantum advantage of about 3dB in measurements of Brillouin gain.

Squeezing-enhancement of optical gyroscopic detection was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Interferometers are highly sensitive to phase differences and are utilized in numerous schemes. Quantum interferometers are able to improve the sensitivity of classical interferometers beyond the shot-noise limit. This is done by employing squeezed states of light and destructive interference of the noise in the system. We developed a quantum SU(1,1) interferometer in the time domain. Our nonlinear quantum interferometer creates interference of the input signals at different times and frequencies. We can control the time and frequency differences for investigating the full temporal and spectral structure of the signal. This quantum interferometer can be utilized for sensing ultrafast phase changes, quantum imaging, temporal mode encoding, and studying the temporal structure of entangled photons.

Precision scanning short-range force sensing with optically trapped nanoparticles was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

We study possibilities of creation and detection of oscillating gravitational fields from high energy laser beams in an optical cavity and from the ultra-relativistic proton bunches circulating in the beam of the Large Hadron Collider (LHC) at CERN. These sources allow for signal frequencies much higher and far narrower in bandwidth than what most celestial sources produce. In addition, by modulating the beams, one can adjust the source frequency over a very broad range, from Hz to GHz. The gravitational field of these sources and responses of three different detectors are analyzed: a Weber-bar-type mechanical rod, a detector based on superfluid helium-4 coupled parametrically to a superconducting microwave cavity, and a monolithic pendulum. We find that with the planned high-luminosity upgrade of the LHC and an improved design of a recently experimentally demonstrated monolithic pendulum, a signal to noise ratio substantially larger than 1 should be achievable. This opens new perspectives of studying general relativistic effects and possibly quantum-gravitational effects with ultra-relativistic, well-controlled terrestrial sources.

We study the fundamental sensitivity that can be achieved with an ideal optomechanical system in the nonlinear regime for measurements of time-dependent gravitational fields. The optomechanical system consists of a cavity mode and a mechanical oscillator coupled to it via (non-linear) radiation pressure coupling. Using recently developed methods to solve the dynamics of a nonlinear optomechanical system with a time-dependent Hamiltonian, we compute the quantum Fisher information for linear displacements of the mechanical element due to gravity. We demonstrate that the sensitivity can be further enhanced by injecting squeezed states of the cavity field or by modulating the light–matter coupling of the optomechanical system. We specifically apply our results to the measurement of gravitational fields from small oscillating masses, where we show that, in principle, the gravitational field of an oscillating nanogram mass can be detected based on experimental parameters that will likely be accessible in the near-term future. Finally, we identify the experimental parameter regime necessary for gravitational wave detection with a quantum optomechanical sensor.

The universal law of gravitation has undergone stringent tests for many decades over a significant range of length scales, from atomic to planetary. Of particular interest is the short distance regime, where modifications to Newtonian gravity may arise from axion-like particles or extra dimensions. We have constructed an ultra-sensitive force sensor based on optically-levitated microspheres for the purpose of investigating non-Newtonian forces that couple to mass with a characteristic scale of 10µm. In this talk I will present the first investigation of the inverse-square law using an optically levitated test mass.

Direct detection of high frequency gravitational waves with cavities was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

This video was recorded for SPIE Photonics West 2022

Stimulated Brillouin scattering (SBS) is a widely studied nonlinear optical effect where light waves interact with traveling acoustic waves. Many applications such as optical fiber sensing, microwave filters or signal manipulation can be realized based on SBS. So far, most research focuses on straight homogenous waveguides and optical fibers. In this work, we report on the experimental investigation of SBS in chiral photonic crystal fibers (PCFs), where the light travels following the helical channels along the waveguide axis. Chiral PCFs robustly maintain circular polarization states and orbital angular momentum (OAM) modes against external perturbations. This allows us to demonstrate the interaction of optical orbital angular momentum (OAM) modes with acoustic waves via SBS. We show pure amplification of circularly polarized light, the first optical vortex Brillouin fiber laser and nonreciprocal devices based on chiral SBS. The results can pave the way to a new generation of Brillouin applications such as in quantum manipulations, optical tweezers, gyroscopes and fiber sensing.

There is growing interest in optical pulses that can be uniquely tailored in both the spatial and time domains. Such dynamic light pulses can be controlled in terms of their propagation properties. The control can be accomplished by combining two different topics, structured light using orthogonal spatial modes and optical frequency combs. By using a set of spatial modes on multiple different comb lines, various types of dynamic spatio-temporal pulses with controllable properties can be produced. This talk will present simulation and experimental results of controllable S-T pulses.

Recent progress in the development of the ultraprecise SNAP platform was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

We present experimental evidence of a 64th order exceptional point realized on a time-multiplexed photonic resonator network. Our highly scalable implementation uses a unidirectionally coupled one-dimensional lattice to achieve higher order exceptional points that are robust to variation in nearest neighbor couplings. Moreover, the non-reciprocal couplings of our network allow for the possibility to exceed the signal to noise limits that restrict other exceptional point implementations.

Fluorescent nanoparticles can probe biological processes on the nanoscale, sometimes with the potential for quantum-enhanced sensing. I will give a brief overview of the field with emphasis on what is still needed. Then I will discuss some particular examples of fluorescent diamond and upconversion phosphor particles that have showed recent promise in these areas.

We report on our progress toward an ultrasensitive Raman-spectroscopic tool for nano-scale probing and imaging of biological objects such as viruses and cells. Our approach is based on laser spectroscopy aided by plasmonic nanoantennas, as in tip-enhanced Raman spectroscopy (TERS). An additional enhancement in sensitivity and speed can be obtained by employing the femtosecond adaptive spectroscopic technique (FAST) for coherent anti-Stokes Raman scattering (CARS). The combined approach will enable nondestructive label-free biosensing with molecular-level sensitivity and with spatial resolution down to a fraction of a nanometer.

Flow cytometry is the most common technique used to probe heterogeneous populations of cells in a high throughput manner. We are interested in the limit when (1) the occurrence of a specific target biomarker is rare and (2) biomarker concentration is low. Here we discuss a framework for in-situ characterizing signal noise levels in those systems, and the use of quantum measurement to optimize detection. Our method enables us to measure biomarker concentration and unambiguously identify the presence of a single emitter from first principles: i.e. without the need for auxiliary calibration.

Optical readout of mechanical devices, operated in both the classical and fully quantum regime, has opened unprecedented levels of sensitivity to small forces and displacements. This has been central to the successful measurement of gravitational waves with LIGO. Here I'll discuss applications of such opto-mechanical systems, ranging in size from single electrons to kilogram-scale masses, to searches for dark matter and for quantum signatures of the gravitational interaction. These detection problems necessitate the use of sensors operated at or beyond noise levels set by the Heisenberg uncertainty principle.

The wave-particle duality of a photon is the bedrock of quantum optics, where both natures are mutually exclusive. Contrary to the conventional understanding of quantum features such as photon bunching on a beam splitter and Bell inequality violation based on the particle nature of photons, a new interpretation is presented for the fundamental understanding of the same quantum features using the wave nature of photons. For this, phase quantization of an optical system interacting with photons is investigated and applied it to a particular quantum phenomenon to fully understand the fundamental concept of indistinguishability between two photons in the quantum feature. This talk opens the door to randomness-based quantum determinacy.

This video was recorded at SPIE Photonics West held in San Francisco, California, United States2022.

This video was recorded for SPIE Photonics West 2022

We report on cooling the center-of-mass motion of a nanoparticle via its interaction with a high finesse cavity. We exploit a hybrid trapping potential obtained by overlapping an electrodynamic potential and an optical standing wave. The coupling can be purely quadratic in displacement and gives rise to a Van der Pol nonlinear damping analogous to parametric feedback. The nanoparticle motion can be cooled by more than two orders of magnitude, and we experimentally demonstrate that the resulting energy distribution is strongly nonthermal. We will also present our initial results on 2D cooling of a tweezer-levitated nanoparticle exploiting coherent scattering.

An optically-levitated microsphere can be driven into rotation by coupling a rotating electric field to the permanent electric dipole moment, resulting in libration about the instantaneous direction of the electric field. This degree of freedom can be cooled by applying a phase modulation to the rotation of the electric field, effectively damping the motion. The degree of cooling is quantified by applying an impulse and observing the resulting exponential decay of the motion, as well as characterizing the thermally driven spectrum librational motion.

Nano-optomechanical structures enable displacement and force sensing with ultimate precision, but their practical application is hindered by the complexity of the optical coupling. Here, we demonstrate that nano-optomechanical sensing can be realized on a fiber-tip without the use of any coupling optics. We use a photonic crystal optomechanical structure fabricated using standard wafer-scale processing. Afterwards the sensors are transferred on a fiber-tip using a simple pickup method. We demonstrate thermomechanical noise measurements with a high signal to noise ratio, using simple reflectance read-out via the fiber.

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. New concepts of matter-wave interferometry can also be used to study the low frequency variations of the strain tensor of space-time and gravitation. For instance, the MIGA instrument, which is currently built in the underground laboratory in Rustrel, France will allow the monitoring of the evolution of the gravitational field at unprecedented sensitivity, which will be exploited both for geophysical studies and for Gravitational Waves (GWs) observations. This present will present the status of this instrument.

Prospects of using entangled quantum networks for quantum sensing was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

A principal goal of distributed quantum processing is the ability to generate, manipulate, and transfer quantum states between distant nodes of a quantum network. These protocols generally require connecting photonic and material carriers of quantum information. Here we present two experimental realizations of light-matter interfaces that allow for engineered atom-photon interactions in free-space settings. First, we utilize reconfigurable arrays of trapped single atoms to study light scattering in low-dimensional systems. We observe noncollinear phase-matching geometries that have suppressed sensitivity to particle localization. We show that the scattered radiation can be controllably enhanced or diminished as a result of Bragg interference. Such scattering can be used for mapping collective states within an array of neutral atoms onto propagating light fields and for establishing quantum links between separated arrays. Second, we create a quasi-two-level system in a regime of Rydberg excitation blockade for a mesoscopic ensemble of several hundred atoms confined in a magic-wavelength optical lattice. We demonstrate coherent driving and Ramsey interference measurements of light shifts, with timescales on the order of ∼ 10 μs. Whereas the coupling producing the Rabi oscillations is enhanced by a factor of √N, there is no corresponding enhancement for the light shifts. These results may prove useful in applying collective qubits with Rydberg interactions to scalable quantum networking architectures.

Rydberg atom electric field sensors offer a number of benefits over traditional antenna-based receivers. They are highly sensitive, small-size, and broadly tunable from near-DC to THz frequencies with a single sensor apparatus. While these sensors are unlikely to replace traditional receivers in many applications owing to their added complexity and narrowband response, they have the potential for a large impact in niche application areas. In this talk, I will highlight viable areas of impact and discuss how their performance compares to that of traditional sensors. Furthermore, I describe the recent progress made on the development of a Rydberg atom-based electric field sensor at MITRE.

A tomography of many-body quantum states of indistinguishable particles is generally performed by engineering couplings between the involved states and a subsequent counting of the occupation numbers. While precise couplings belong to the standard experimental toolbox, an accurate number counting presents a considerable challenge for both photonic and atomic quantum states. Here we present an application of a number-resolving atom counting [New J. Phys. 23, 113046 (2021)] for the state reconstruction of an atomic coherent spin state. We generate the coherent spin state by driving a Rabi frequency between two hyperfine states of an ultracold Rubidium ensemble.The result is analyzed by a number-resolving fluoresence detection setup. We characterize the fidelity of our detector and show that a negative-valued Wigner function is associated with it. The results offer an exciting perspective for a high-fidelity tomography of entangled states and can be applied for the future demonstration of Heisenberg-limited atom interferometry.

Neutral atoms and nanophotonics: a platform for quantum devices on chip was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

Hybrid quantum devices, incorporating both atoms and photons, are able to exploit the benefits of both systems. Compact, robust atom-photon interfaces will enable scalable architectures for quantum computing and quantum communication, as well as chip-scale sensors and single-photon sources. We demonstrate a new type of interface and show the interaction of cold cesium atoms with resonant photons. For this atoms are cooled in a magneto-optical trap, transferred to an optical dipole trap and positioned inside a transverse, 30 µm diameter through-hole in an optical fibre, created via laser micromachining. The intersection is orthogonal to the propagation direction of the light mode. We trap about 300 atoms at a temperature of 120µK. When the guided light is on resonance with the caesium D2 line, up to 87% of it is absorbed by the atoms. Our technique can be applied in 2-dimensional systems, i.e. in optical waveguide chips and other existing photonic systems. We also discuss the influence of hole shapes on transmission and prospects of adding a micro-cavity.

We present a method of using a high-flux entangled photon-pair source to improve the signal-to-noise ratio of a single-pixel imaging system. Sensing with single-photon counting detectors will often suffer from measurement noise due to any background light levels. Using a single detector enables a high efficiency of detection and when paired with a variable transmission mask enables full images to be captured. The heralding photon from the source acts as a temporal reference, allowing the signal photons to be distinguished from background noise. This heralding method is key to understanding how quantum measurements can produce higher contrast images than their classical equivalent.

The memory effect in disordered systems is a key physical phenomenon that has been employed for optical imaging, metrology, and communication through opaque media. Under the conventional memory effect, when the incident beam is tilted slightly, the transmitted pattern tilts in the same direction. However, the “memory” is limited in its angular range and tilt direction. We customize the memory effect by introducing an angular memory operator. Its eigenstates possess perfect correlation for tilt angles and directions that can be arbitrarily chosen separately for the incident and transmitted waves. Customized memory effects have been demonstrated experimentally with wavefront shaping.

We show that exceptional points in conservatively coupled systems can increase the quantum-limited precision of laser gyroscopes as a result of gain saturation, but that this requires recovery of the beat note by interference with an auxiliary mode, with consequences for the quantum and classical noise that depend on the particular recovery scheme.

We report the experimental demonstration of real-time magnetometry by detecting fluorescence from a nitrogen vacancy center in the setting of coherent population trapping and by estimating magnetic fields from the time series of the observed photon counts. We show that by taking into consideration the statistical properties of magnetic field fluctuations, a Bayesian inference-based estimator can effectively update dynamical information of the field in real time with the detection of just a single photon.

This video was recorded for Photonics West 2022

Application of ODMR techniques with colour centres in diamond to temperature measurement in neurons G.Petrini, G.Tomagra, E.Bernardi, E,. Moreva, I.P.Degiovanni, P.Traina, P.Olivero, V.Carabelli, M.Genovese In this talk I will present our results that demonstrate for the first time the possibility of making localized temperature measurement with precision under 0.1 K in neurons by exploiting ODMR techniques. After a general introduction to ODMR techniques based on NV colour centers in diamond, I will present this breakthrough result Than could have huge possible impact to biology and medicine.

We report on the application of ultra-sensitive, nanophotonics-based sensors for temperature metrology. In particular, we present details on implementing an advanced laser locking technique to interrogate a nanobeam photonic crystal cavity temperature sensor. Our measurement technique allows a fully continuous, wide temperature rage sensor readout without breaking a laser lock over 280°C temperature range: from -40°C to 240°C, in real-time. We provide details on sensor design and fabrication, as well the measurement setup based on an advanced laser locking technique. Our photonic sensor interrogation approach can advance the photonics thermometry towards field-deployable measurement solutions.

This video was recorded for Photonics West 2022

Recent works showed that the separation between two point sources can be estimated at the quantum limit using intensity measurements after spatial-mode demultiplexing. However, so far these results have been either limited to low-intensity, or thermal sources. In this talk, we will present an analytical expression for the Quantum Fisher Information for the separation between two sources in an arbitrary Gaussian states. This expression allows us to determine the ultimate resolution limit for a series of practically relevant states, e.g. correlated or displaced thermal states (corresponding to partially coherent sources) and squeezed states (exhibiting quantum correlations). Moreover, we will show how a simple estimation technique, requiring access only to the mean value of a linear combination of demultiplexed intensity measurements can be used to saturate these limits. Finally, we will discuss the applicability of the proposed methods in present experimental setups.

This video was recorded for Photonics West 2022

This video was recorded for Photonics West 2022

Trace-gas plume reconstruction and source localization using drone-assisted remote molecular dispersion spectroscopy was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

A chip-based Brillouin gyroscope was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

We demonstrate a compact light-pulse atom interferometer (LPAI) with a high data-rate grating magneto-optical trap (GMOT) and a photonic-integrated-circuit (PIC)-compatible laser system. These efforts are aligned with one of our primary goals, LPAI operation in high-dynamic environments through ruggedization and miniaturization of the sensor head and laser systems. The compact sensor head is based on a custom vacuum package and a grating chip with fixed optical components. The high data-rate LPAI operation with a GMOT enables the operation of LPAIs in high dynamics. PIC-compatible and PIC-based laser systems are realized and used to demonstrate LPAIs towards miniature cold-atom inertial sensors. Acknowledgement This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories and is funded under the DARPA APhI program. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the view of the U.S. Department of Energy or the United States Government.

We study the excitation of the quantum coherence in a $\Lambda$-type molecular media and its influence on chirped pulse propagation. The coherent population trapping (CPT) of the ground states in the $\Lambda$-system results in fascinating new dynamics of pulse propagation through it. We have considered the two- and three-level molecules. The dressed state basis approach is employed, which provides deep physical insights showing interaction of “bright” and “dark” states with radiation. The level structure of the model is common for the molecular media, where the ground states maybe the ro-vibrational levels of the ground electronic state. We consider a gas of three-level atoms or molecules in the presence of two coherent optical pulses. We demonstrate the importance of role of the dark states. The presented results are important for applications to manipulation of quantum states for molecular detection in engineering, chemical, and biological applications.

Since the introduction of the intensity interferometer by Hanbury Brown and Twiss in the '50s and its subsequent adaptations to quantum optic experiments, photon correlations have played a significant role in optical research. An emerging detector technology, SPAD arrays, presents new opportunities to scale these experiments and exploit photon correlations in new regimes. I will describe a new temporal-spectral photon correlation technique based on these detectors, single-particle heralded spectroscopy. I will present new insights into the photophysics of multiply-excited semiconductor quantum dots uncovered by this method, hitherto inaccessible to existing approaches.

The result of a phase measurement is generally observed as an amplitude modulation of passively interfering sample and reference beams. Here, in contrast, the measuring interferometer and the laser source are combined as a single unit. A beat frequency (phase shift per round-trip) instead of a noisy amplitude modulation are recorded. This sensor circulates two pulses with the same group velocity in a laser or Optical parametric Oscillator (OPO) cavity; one pulse serves as reference while the phase of the other is affected at each round-trip by the parameter to be measured. We consider as an example a linear polarization maintaining (PM) fiber OPO in which two orthogonal pulses circulate. The cavity is terminated by a Michelson like interferometer consisting in a polarization splitter sending each pulse in a different arm. The classical noise in that configuration is very high, since a difference in length of the two arms produced a beat note in the tens of MHz. To analyze the quantum limit of noise, the Michelson termination is replaced by a single end mirror in a discrete components double comb OPO. The two combs to be interfered exist in exactly the same cavity, and thus have correlated noise. Fine control of the beat frequency is achieved with an intracavity phase modulator. Preliminary measurements show a bandwidth of 2 mHz at a beat note frequency of 1 Hz (phase shift of 1:5 · 10 -7). A theoretical simulation of the spectral evolution of the pulses at each round-trip shows how the beat note develops in presence or absence of coupling between the two beams. The simulation shows that the beat note frequency is enhanced, without noise penalty, by inserting resonant dispersion in the cavity. Preliminary results with a Gires Tounois as end cavity mirror agree with the simulation.

This video was recorded at SPIE Photonics West held in San Francisco, California, United States 2022

This video has been recorded for Photonics West 2022

Integrated photonics is providing a compelling route for quantum limited and quantum enhanced technologies, including computing communications and optical sensing. This is because chip-scale integrated photonics can offer miniaturization as well as possible scalability in manufacture. Here we will discuss recent results in developing integrated homodyne detection integrated in silicon photonics. We discuss its combination with integrated electronics to demonstrate high bandwidth performance and its use to measure squeezed light over a broad bandwidth, out to 9GHz. This demonstrates a performance enhancement that is relevant to quantum technology and is due to miniaturization. We will discuss possible applications of of integrated quantum noise listed homodyne detection, including a strategy to perform quantum limited absorption estimation using integrated photonics and coherent states.

This video was recorded for SPIE Photonics West 2022

This video was recorded for Photonics West 2022

This video was recorded for SPIE Photonics West 2022

Sizing of individual particles with nanoscale precision is crucial for the understanding of their physical and chemical properties and for their use in nanodevices. Optical characterization methods are rapid, non-invasive and may provide a wide range of useful information. However, the weak optical response of subwavelength wide-gap dielectric nanoparticles poses a fundamental challenge for their optical metrology. We demonstrate scalable optical sizing of nanodiamonds based on confocal scanning microscopy. The method is absolutely calibrated by an atomic force microscope and paves the way for the facile metrology of a wide range of weakly scattering nano-objects for applications in biomedicine, catalysis, nanotechnology, and quantum optics.

Interfacing cold atoms with nanoscale photonic structures promises stronger atom-light interactions and novel quantum functionalities via dispersion engineering, controlled photon propagation, topology, and chiral quantum transport. Recent years have seen advances in a number of atom-nanophotonics platforms with suspended nanostructures. However, extending such a system to planar structures faces immediate challenges due to reduced trap loading and laser cooling efficiency directly on a dielectric plane. In this talk, we will show experimental demonstration of precision guiding and trapping cold atoms in the near field of a planar nanophotonic circuit, and realization of large atom-photon coupling to a whispering-gallery mode in a microring resonator.

We report on the softest micro-resonator at room conditions. The softness of our resonator is limited by Brownian motion, tearing the resonator apart, when we attempt to make it softer. For comparison; our resonator exhibits a smaller interfacial tension than the air-liquid interface of liquid Helium II. While coupling light to the resonator, we can gradually deform it with holographic optical tweezers, changing it's functionality. We observe directional emission out of the micro-resonator cavity and can split a whispering-gallery resonate mode to a 10-GHz separated doublet. We measure an optical quality of 10^5

We demonstrate a highly sensitive approach for concentration measurements by Michelson interferometry with twisted helical light beams. When superimposing two helical light beams with opposing topological charge, a characteristic daisy flower interference pattern is generated which rotates when a phase shift is introduced in one of the interferometer arms. By analyzing the change in the interference pattern caused by a microfluidic sample, we can determine the refractive index and therefore the concentration of aqueous samples such as glucose and NaCl minimally invasive and label-free with a sensitivity on the order of 10e-6 refractive index units.

Photoinduced second harmonic generation and optical parametric oscillation in silicon-based microresonators was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.

We study two potential systematic errors which affect precision measurements of the collision shift of an unresolved multi-component Doppler-broadened resonance: the optical intensity-dependent shift of the absorption resonance peak and the temperature dependence of the shift of the resonance peak. Experiments with 87Rb reveal an intensity-dependent shift of the D2, F=2, F' resonance. We interpret the shift to be the result of reshaping of the resonance profile by optical pumping on two of the three hyperfine components, with the pumping rate differing when argon perturbers are present. Furthermore, the multi-component Doppler-broadened resonance exhibits a temperature-dependent shift in the theoretical profile for the resonance. Accurate measurement of the collision shift for such resonances, at a precision of a few MHz, requires consideration of the intensity and temperature-dependent effects.

This video was recorded for SPIE Photonics West 2022

Due to its simple level structure, helium 4 is particularly attractive to investigate original scenario for nonlinear light-atom interaction. We illustrate this feature by two examples: i) the demonstration of an original CPT-enhanced phase sensitive amplifier for light, which has been used to generate a squeezed vacuum and, ii) the originality of spin noise spectroscopy in metastable helium 4.

This video has been recorded for Photonics West 2022

Inertial sensors based on cold atoms and light-pulse interferometry exhibit state-of-the-art sensitivity and ultra-low measurement bias that could revolutionize a variety of fields including geophysics and seismology, gravitational wave detection and fundamental tests of gravity, and inertial navigation. In the latter case, cold-atom interferometers are widely considered as breakthrough technology for future autonomous INSs. Nowadays, absolute quantum inertial sensors are available as commercial and field-deployable devices. Yet, their current size and complexity has not yet reached a technology readiness level compatible with mobile applications or plug-and-play operation by non-specialists. These systems are in desperate need of further development and miniaturization. We will present progress beyond these first experiments while exploring new methods relying on 3D matter-wave manipulation that can lead to interferometer geometries that are simultaneously sensitive to accelerations and rotations in 3D and can discern their vector components within a single measurement. These novel innovations produce additional sensitivity to rotations and gravity gradients which has not yet been exploited experimentally and could be a game changing innovation for future atomic sensors. The ability to measure the full acceleration and rotation vectors with a compact, high-precision, low-bias inertial sensor could strongly impact the fields of inertial navigation, gravity gradiometry, and gyroscopy.

This video was recorded for Photonics West 2022

This video Multiphoton approximation error of parametric down conversion source detection was recorded for Photonics West on Demand 2022.

This video has been recorded for Photonics West 2022

Quantum-enhanced stimulated Raman scattering (QE-SRS) becomes a powerful method for high-sensitivity molecular vibrational spectroscopy and imaging by breaking the shot-noise-limited sensitivity of classical SRS. However, it’s still challenging to achieve quantum-enhancement with typical pulse power (<10-mW) for SRS. Although amplitude-squeezing technique was utilized in the previous QE-SRS, it limits the available optical power by its deamplification or optical loss at asymmetric beamsplitter. To circumvent this problem, we propose and demonstrate SRS spectroscopy with quantum-enhanced balanced detection (QE-BD) scheme, where squeezed vacuum (SQV) is combined with a strong local oscillator (LO) to enhance the sensitivity of SRS. We generated SQV at the central wavelength of 844-nm, using a periodically-poled stoichiometric LiTaO3 waveguide. Picosecond LO light is modulated by a spatial light modulator to achieve spatial matching with SQV , and resultant high squeezing level. At each photodiode, LO has ~10-mW optical power, and –3.1-dB squeezing level was observed. To obtain the QE-SRS spectrum of dimethyl sulfoxide-d6 (d-DMSO), we scanned the wavelength of Stokes laser by a high-speed spectral scanner composed of a grating and galvanometric scanner . The QE-SRS spectrum in the wavenumber range of 1950-2300-cm-1 was acquired with 2.1-dB signal-to-noise ratio (SNR) improvement compared with classical shot-noise-limited SRS under balanced-detection. The proposed QE-BD SRS paves the way for QE-SRS with high-power pulses, and shows a potential to exceed the SNR of state-of-the-art classical SRS system without quantum enhancement

Spin defects in solids (e.g. diamond) have been widely used for quantum sensing of temperature and magnetic fields. The recent discovery of spin qubits in hexagonal boron nitride (hBN), a van der Waals material, provides new opportunities for quantum sensing. For example, spin qubits in hBN will be particularly suitable for studying 2D magnetic materials. However, the brightness and the contrast of boron vacancy spin defects in hBN are relatively low, which limit their applications in quantum sensing. Recently, we created spin defects in hBN by both femtosecond laser writing [ACS Photonics, 8, 994 (2021)] and ion implantation, and enhanced the brightness of hBN spin defects by a factor of 17 with gold surface plasmons [Nano Letters, 21, 7708 (2021)]. We also observed a record-high contrast of the optically detected magnetic resonance (ODMR) of hBN spin defects at room temperature. Our work show hBN spin defects are promising for quantum sensing.

This video was recorded for Photonics West 2022