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[IEEE 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Amsterdam (2018.8.27-2018.8.30)] 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - High-Resolution Near-Field Imaging and Far-Field Antenna Measurements with Atomic Sensors
摘要： Measurements of radio-frequency (RF) electric fields using atomic sensors based on quantum-optical spectroscopy of Rydberg states in vapors has garnered significant interest in recent years for the establishment of atomic standards for RF electric fields and towards the development of novel RF sensing instrumentation. Here we describe recent work employing atomic sensors for sub-wavelength near-field imaging of a Ku-band horn antenna. We demonstrate near-field imaging capability at a spatial resolution of λ/10 and measurements over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a Rydberg-atom resonance. A fiber-coupled atomic-sensor probe is also employed in far-field measurements of a WR-90 standard gain horn.
关键词： electromagnetic compatibility,Rydberg,atom,quantum sensing,RF,metrology,antenna characterization,microwave,Atomic sensors,electric field,antenna,radio-frequency
更新于2025-09-23 15:23:52
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Repeater-enhanced distributed quantum sensing based on continuous-variable multipartite entanglement
摘要： Entanglement is a unique resource for quantum-enhanced applications. When employed in sensing, shared entanglement between distributed quantum sensors enables a substantial gain in the measurement sensitivity in estimating global parameters of the quantum sensor network. Loss incurred in the distribution of entanglement, however, quickly dissipates the measurement-sensitivity advantage enjoyed by the entangled quantum sensors over sensors supplied with local quantum resources. Here we present a viable approach to overcome the entanglement-distribution loss and show that the measurement sensitivity enabled by entangled quantum sensors beats that afforded by the optimum local resource. Our approach relies on noiseless linear amplifiers (NLAs) to serve as quantum repeaters. We show that, unlike the outstanding challenge of building quantum repeaters to suppress the repeaterless bound for quantum key distribution, NLA-based quantum repeaters for distributed quantum sensing are realizable by available technology. As such, distributed quantum sensing would become an application instance that benefits from quantum repeaters.
关键词： quantum repeaters,distributed quantum sensing,entanglement,quantum sensing,noiseless linear amplifiers
更新于2025-09-23 15:22:29
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<i>Ab Initio</i> Spin-Strain Coupling Parameters of Divacancy Qubits in Silicon Carbide
摘要： Cubic silicon carbide is an excellent platform for integration of defect qubits into established wafer-scale device architectures for quantum information and sensing applications, where a divacancy qubit, which is similar to the negatively charged nitrogen-vacancy (NV) center in diamond, has favorable coherence properties. We demonstrate by means of density-functional-theory calculations that for most types of distortion the 3C divacancy exhibits slightly smaller spin-strain coupling parameters but greater spin-stress coupling parameters in comparison with the diamond NV. We predict that high-quality 3C-SiC thin films hosting divacancy qubits are prospective platforms for quantum-enhanced pressure-sensor devices.
关键词： spin-strain coupling,quantum sensing,density-functional theory,divacancy qubits,silicon carbide
更新于2025-09-23 15:21:01
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Modelling of Cavity Optomechanical Magnetometers
摘要： Cavity optomechanical magnetic ?eld sensors, constructed by coupling a magnetostrictive material to a micro-toroidal optical cavity, act as ultra-sensitive room temperature magnetometers with tens of micrometre size and broad bandwidth, combined with a simple operating scheme. Here, we develop a general recipe for predicting the ?eld sensitivity of these devices. Several geometries are analysed, with a highest predicted sensitivity of 180 pT/√Hz at 28 μm resolution limited by thermal noise in good agreement with previous experimental observations. Furthermore, by adjusting the composition of the magnetostrictive material and its annealing process, a sensitivity as good as 20 pT/√Hz may be possible at the same resolution. This method paves a way for future design of magnetostrictive material based optomechanical magnetometers, possibly allowing both scalar and vectorial magnetometers.
关键词： magnetometer,quantum sensing,cavity-optomechanics
更新于2025-09-23 15:21:01
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Collectively induced exceptional points of quantum emitters coupled to nanoparticle surface plasmons
摘要： Exceptional points, resulting from non-Hermitian degeneracies, have the potential to enhance the capabilities of quantum sensing. Thus, finding exceptional points in different quantum systems is vital for developing such future sensing devices. Taking advantage of the enhanced light-matter interactions in a confined volume on a metal nanoparticle surface, here we theoretically demonstrate the existence of exceptional points in a system consisting of quantum emitters coupled to a metal nanoparticle of subwavelength scale. By using an analytical quantum electrodynamics approach, exceptional points are manifested as a result of a strong-coupling effect and observable in a drastic splitting of originally coalescent eigenenergies. Furthermore, we show that exceptional points can also occur when a number of quantum emitters are collectively coupled to the dipole mode of localized surface plasmons. Such a quantum collective effect not only relaxes the strong-coupling requirement for an individual emitter, but also results in a more stable generation of the exceptional points. Furthermore, we point out that the exceptional points can be explicitly revealed in the power spectra. A generalized signal-to-noise ratio, accounting for both the frequency splitting in the power spectrum and the system’s dissipation, shows clearly that a collection of quantum emitters coupled to a nanoparticle provides a better performance of detecting exceptional points, compared to that of a single quantum emitter.
关键词： strong-coupling effect,metal nanoparticle,power spectra,quantum emitters,quantum sensing,signal-to-noise ratio,surface plasmons,Exceptional points
更新于2025-09-23 15:19:57
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Robust and efficient quantum optimal control of spin probes in a complex (biological) environment. Towards sensing of fast temperature fluctuations
摘要： We present an optimized scheme for nanoscale measurements of temperature in a complex environment using the nitrogen-vacancy center in nanodiamonds (NDs). To this end we combine a Ramsey measurement for temperature determination with advanced optimal control theory. We test our new design on single nitrogen-vacancy centers in bulk diamond and fixed NDs, achieving better readout signal than with common soft or hard microwave control pulses. We demonstrate temperature readout using rotating NDs in an agarose matrix. Our method opens the way to measure temperature fluctuations in complex biological environment. The used principle is universal and not restricted to temperature sensing.
关键词： quantum sensing,temperature measurement,nanodiamonds,optimal control
更新于2025-09-19 17:15:36
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[IEEE 2018 11th Global Symposium on Millimeter Waves (GSMM) - Boulder, CO, USA (2018.5.22-2018.5.24)] 2018 11th Global Symposium on Millimeter Waves (GSMM) - High-Resolution Antenna Near-Field Imaging and Sub-THz Measurements with a Small Atomic Vapor-Cell Sensing Element
摘要： Atomic sensing and measurement of millimeter-wave (mmW) and THz electric fields using quantum-optical EIT spectroscopy of Rydberg states in atomic vapors has garnered significant interest in recent years towards the development of atomic electric-field standards and sensor technologies. Here we describe recent work employing small atomic vapor cell sensing elements for near-field imaging of the radiation pattern of a Ku-band horn antenna at 13.49 GHz. We image fields at a spatial resolution of λ/10 and measure over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a Rydberg resonance. The same atomic sensing element is used to measure sub-THz electric fields at 255 GHz, an increase in mmW-frequency by more than one order of magnitude. The sub-THz field is measured over a continuous ±100 MHz frequency band using a near-resonant mmW atomic transition.
关键词： atom,microwave,electric field,metrology,quantum sensing,millimeter-wave,THz,antenna,mmW,Rydberg,terahertz,Atomic sensors,antenna characterization
更新于2025-09-19 17:15:36
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Distributed quantum sensing in a continuous-variable entangled network
摘要： Networking is integral to quantum communications1 and has significant potential for upscaling quantum computer technologies2. Recently, it was realized that the sensing performances of multiple spatially distributed parameters may also be enhanced through the use of an entangled quantum network3–10. Here, we experimentally demonstrate how sensing of an averaged phase shift among four distributed nodes benefits from an entangled quantum network. Using a four-mode entangled continuous-variable state, we demonstrate deterministic quantum phase sensing with a precision beyond what is attainable with separable probes. The techniques behind this result can have direct applications in a number of areas ranging from molecular tracking to quantum networks of atomic clocks.
关键词： continuous-variable,distributed phase sensing,quantum sensing,entangled network
更新于2025-09-12 10:27:22
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Physical-Layer Supervised Learning Assisted by an Entangled Sensor Network
摘要： Many existing quantum supervised learning (SL) schemes consider data given a priori in a classical description. With only noisy intermediate-scale quantum (NISQ) devices available in the near future, their quantum speedup awaits the development of quantum random access memories (qRAMs) and fault-tolerant quantum computing. However, there also exist a multitude of SL tasks whose data are acquired by sensors, e.g., pattern classification based on data produced by imaging sensors. Solving such SL tasks naturally requires an integrated approach harnessing tools from both quantum sensing and quantum computing. We introduce supervised learning assisted by an entangled sensor network (SLAEN) as a means to carry out SL tasks at the physical layer. The entanglement shared by the sensors in SLAEN boosts the performance of extracting global features of the object under investigation. We leverage SLAEN to construct an entanglement-assisted support-vector machine for data classification and entanglement-assisted principal component analyzer for data compression. In both schemes, variational circuits are employed to seek the optimum entangled probe states and measurement settings to maximize the entanglement-enabled enhancement. We observe that SLAEN enjoys an appreciable entanglement-enabled performance gain, even in the presence of loss, over conventional strategies in which classical data are acquired by separable sensors and subsequently processed by classical SL algorithms. SLAEN is realizable with available technology, opening a viable route toward building NISQ devices that offer unmatched performance beyond what the optimum classical device is able to afford.
关键词： Quantum supervised learning,Support-vector machine,Entangled sensor network,Principal component analyzer,Quantum computing,Quantum sensing
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Quantum Sensing of Absorbance and the Beer-Lambert Law
摘要： Optical quantum sensing strategies that utilise features of quantum states of light have implications for precision measurement in areas as wide ranging as such as gravitational wave sensing and biological imaging. Optical absorption estimation is the task of estimating the transmission parameter η which is defined by the ratio of input, (cid:1835)(cid:3036)(cid:3041), to output, (cid:1835)(cid:3042)(cid:3048)(cid:3047), intensity of light from a sample of interest ((cid:1835)(cid:3042)(cid:3048)(cid:3047) = (cid:2015)(cid:1835)(cid:3036)(cid:3041)). The optimal quantum strategy provides a quantum advantage (per incident photon) of 1/(1-η) over the best classical strategy. This technique has been demonstrated experimentally in single parameter estimation and imaging scenarios. Here, we expand on recent theoretical and experimental results and investigate the quantum advantage available for absorbance estimation, where the parameter of interest, α, is the loss per unit length parameter used in the Beer-Lambert law: (cid:1835)(cid:3042)(cid:3048)(cid:3047) = exp(?α (cid:1838))(cid:1835)(cid:3036)(cid:3041), where (cid:1838) is the length of the sample. We further show that the tunability of (cid:1838) allows for maximisation of the Fisher information. Furthermore, we show that the optimal length, (cid:1838)(cid:3042)(cid:3043)(cid:3047), that provides the largest Fisher information is a function of the photon number statistics of the input optical state, and as such is different for optimal quantum and classical schemes. When both strategies are operating at (cid:1838)(cid:3042)(cid:3043)(cid:3047), the quantum advantage is limited to a fixed value of 1.2 for all α, contrary to absorption estimation where the quantum advantage can be arbitrarily large. This demonstrates that an improvement in the precision of the sensor can be performed by classical means, drastically reducing the advantage offered by quantum strategies. We find the impact of (cid:1838)(cid:3042)(cid:3043)(cid:3047) is analogous to previous work looking at multipass strategies for phase estimation. Using the setup depicted in Figure 1, we experimentally show that for single photon Fock states, optimising over (cid:1838) does indeed yield higher precision estimates of absorbance. This work has implications for a range of experiments employing the Beer-Lambert law, and can be expanded to include other experimental parameters such as loss, dark counts, and noisy laser sources.
关键词： Absorbance,Quantum Advantage,Fisher Information,Beer-Lambert Law,Quantum Sensing
更新于2025-09-11 14:15:04