Optical and Quantum Sensing and Precision Metrology II
Expanding the reach of quantum optical sensing: from the microscopic scale to the metropolitan scale
Hari Prasad Lamsal, Priya Drashni, Kazi Reaz, Vsevolod D. Cheburkanov, Md Mehdi Hassan, Jacob E. Humberd, Matthew L. Boone, Angel Fraire Estrada, Rick Mukherjee, H. R. Sadeghpour, Vladislav V. Yakovlev, Marlan O. Scully, G. S. Agarwal, George Siopsis, Tian Li
Quantum sensing harnesses squeezing, entanglement, and quantum correlations to surpass classical measurement limits. This work highlights our efforts to extend measurement capabilities from microscopic biological systems to metropolitan-scale networks. At the microscopic level, we demonstrate squeezed-light–enhanced Brillouin microscopy for label-free probing of cellular mechanics, achieving higher imaging contrast with reduced photodamage and significantly improved viability in live cancer cells and brain tissue. At the macroscopic level, we report the first distribution of multi-photon entanglement across a deployed commercial fiber network in downtown Chattanooga, establishing heralded Bell and N00N states between distant network nodes. Together, these advances show that quantum optics can unify applications from microscopy to metro-scale networks, signaling a future where quantum optical sensing evolves into a widely deployed and scalable technology.
Quantum sensing harnesses squeezing, entanglement, and quantum correlations to surpass classical measurement limits. This work highlights our efforts to extend measurement capabilities from microscopic biological systems to metropolitan-scale networks. At the microscopic level, we demonstrate squeezed-light–enhanced Brillouin microscopy for label-free probing of cellular mechanics, achieving higher imaging contrast with reduced photodamage and significantly improved viability in live cancer cells and brain tissue. At the macroscopic level, we report the first distribution of multi-photon entanglement across a deployed commercial fiber network in downtown Chattanooga, establishing heralded Bell and N00N states between distant network nodes. Together, these advances show that quantum optics can unify applications from microscopy to metro-scale networks, signaling a future where quantum optical sensing evolves into a widely deployed and scalable technology.
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. In this talk I will report recent work from my laboratory which demonstrates this absolute quantum advantage [1]. We show, specifically, that quantum correlations enable signal-to-noise beyond the photodamage-free capacity of conventional microscopy. Broadly, this represents the first demonstration that quantum correlations can allow sensing beyond the limits introduced by optical intrusion upon the measurement process. 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.
Much of our progress in understanding microscale biology has been powered by advances in microscopy. For instance, super-resolution microscopes allow the observation of biological structures at near-atomic-scale resolution, while multi-photon microscopes allow imaging deep into tissue. However, biological structures and dynamics still often remain out of reach of existing microscopes, with further advances in signal-to-noise, resolution and speed needed to access them. In many cases, the performance of microscopes is now limited by quantum effects – such as noise due to the quantisation of light into photons or, for multi-photon microscopes, the low cross-section of multi-photon scattering. These limitations can be overcome by exploiting features of quantum mechanics such as entanglement. Quantum effects can also provide new ways to enhance the performance of microscopes, such as new super-resolution techniques and new techniques to image at difficult to reach wavelengths. This review provides an overview of these various ways in which quantum techniques can improve microscopy, including recent experimental progress. It seeks to provide a realistic picture of what is possible, and what the constraints and opportunities are.
Quantum-enhanced sensing has emerged as a transformative technology with the potential to surpass classical sensing modalities in precision and sensitivity.This study explores the advancements and applications of quantum-enhanced sensing, emphasizing its capacity to bridge fundamental physics and practical implementations.The current progress in experimental demonstrations of quantum-enhanced sensing systems was reviewed, focusing on breakthroughs in metrology and the development of physically realizable sensor architectures.Two practical implementations of quantum-enhanced sensors based on trapped ions were proposed.The first design utilizes Ramsey interferometry with spin-squeezed atomic ensembles, employing laser-induced spin-exchange interactions to reconstruct the sensing Hamiltonian.This approach enables measurement rates to scale with the number of sensing atoms, achieving sensitivity enhancements beyond the standard quantum limit (SQL).The second implementation introduces mean-field interactions mediated by coupled optical cavities that share coherent atomic probes, enabling the realization of high-performance sensing systems.Both sensor systems were demonstrated to be feasible on state-ofthe-art ion-trap platforms, offering promising benchmarks for future applications in metrology and imaging.Particular attention was given to the integration of quantum-enhanced sensing with complementary imaging technologies, which continues to gain traction in medical imaging and other fields.The mutual reinforcement of quantum and complementary technologies is increasingly supported by significant investments from governmental, academic, and commercial entities.The ongoing pursuit of improved measurement resolution and imaging fidelity underscores the interdependence of these innovations, advancing the transition of quantum-enhanced sensing from fundamental research to widespread practical use.
Non-invasive cancer diagnostics aim to detect tumors as early as possible without harming the patient. In this project, I explore how quantum photonics can improve medical imaging by using the quantum properties of light to reach subcellular precision. The main idea is to compare classical optical coherence tomography (OCT) with quantum-enhanced imaging that uses single photons, entangled photon pairs, and squeezed-light states. Using a conceptual device model, I examine how quantum light sources could reduce photonic noise, improve contrast, and allow repeated imaging with minimal damage to sensitive tissues. Literature on quantum imaging, biophotonics, and cancer diagnostics is reviewed to connect these ideas to current research in early tumor detection. These studies report gains in axial resolution, depth penetration, and signal-to-noise ratio when quantum effects are used. The project also considers ethical questions, such as fair access, cost, and data privacy, when introducing advanced quantum technologies into healthcare. Overall, the work suggests that quantum photonics can help build safer, faster, and more accurate imaging systems for cancer diagnostics, while supporting responsible and inclusive medical innovation.
Quantum sensors emerged among quantum technologies as the ones with promising potential applications in the near future. This perspective reviews two leading quantum sensing platforms and their advancements toward biological applications: quantum light sources and color centers in diamonds. Quantum light, including squeezed states and N00N states, allows enhanced phase measurements by surpassing the classical shot noise limits. This advantage can be exploited in several contexts, enabling improved resolution and sensitivity, which are particularly valuable in biological contexts where traditional high-intensity illumination could damage or alter delicate samples. In parallel, color centers in diamonds, specifically nitrogen-vacancy and silicon-vacancy centers, also emerged as promising for sensing applications due to their high sensitivity and biocompatibility. These sensors enable detailed intracellular measurements, such as temperature detection, and show potential for measuring magnetic fields of biological origin. Despite these advancements, significant challenges remain in translating these technologies from a controlled laboratory environment to practical, widely applicable devices for diverse biological applications. Overcoming these challenges is crucial for unlocking the full potential of quantum sensors in the biological field.
Quantum resources such as squeezed and entangled states of light provide a pathway to surpass classical sensitivity limits in measurement and information processing. This thesis presents the development and application of engineered squeezed light sources across both bulk and integrated photonic platforms, demonstrating their utility in advancing quantum-enhanced metrology for spectroscopy and inertial sensing. In the first experimental platform, I introduce entangled dual-comb spectroscopy (EDCS), which integrates squeezed light with dual-comb architectures. By exploiting entanglement across comb lines, EDCS circumvents the shot-noise limitations of classical dual-comb spectroscopy. My experiment demonstrate a 2.6 dB improvement in signal-to-noise ratio and a 1.7-fold reduction in integration time, establishing EDCS as a powerful tool for rapid and precise chemical and biological sensing. The second platform applies squeezed light to resonant fiber optic gyroscopes (RFOGs), where quantum fluctuations typically impose a fundamental noise floor. By injecting bright amplitude-squeezed light into the resonator, I achieve a 2 dB reduction in detector noise, verified via Allan deviation analysis. This quantum-enhanced RFOG architecture shows that squeezed light can improve sensitivity under practical operational conditions, paving the way for next-generation inertial navigation systems. Finally, I demonstrate the on-chip generation of squeezed light using silicon nitride photonic circuits. Thin-film devices achieve more than 2 dB of quadrature squeezing with excellent agreement between experiment and theory, while wafer-scale thick-film devices yield reproducible 3 dB squeezing across multiple dies with sub-0.2 dB variation. These results establish silicon nitride as a CMOS-compatible platform for scalable and manufacturable quantum light sources, offering a route toward robust, large-scale quantum photonic technologies. Together, these results bridge the gap between laboratory demonstrations and deployable quantum-enhanced measurement systems. By advancing both free-space and integrated implementations of squeezed light, this work provides foundational steps toward practical quantum technologies for precision navigation, spectroscopy, and information processing.