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Quantum LiDAR leverages nonclassical light states, quantum correlations, and advanced detection schemes to enhance sensitivity, resolution, and noise resilience in active optical ranging. This review presents the theoretical principles underpinning quantum LiDAR, surveys experimental milestones, and compares the quantum advantage provided against classical LiDAR systems.

Optical frequency division via optical frequency combs has enabled a leap in microwave metrology, leading to noise performance never explored before. Extending this method to the millimetre-wave and terahertz-wave domains is of great interest. Dissipative Kerr solitons in integrated photonic chips offer the unique feature of delivering optical frequency combs with ultrahigh repetition rates from 10 GHz to 1 THz, making them relevant gears for performing optical frequency division in the millimetre-wave and terahertz-wave domains. We experimentally demonstrate the optical frequency division of an optically carried 3.6 THz reference down to 300 GHz through a dissipative Kerr soliton, photodetected with an ultrafast uni-travelling-carrier photodiode. A new measurement system, based on the characterization of a microwave reference phase locked to the 300 GHz signal under test, yields attosecond-level timing-noise sensitivity, overcoming conventional technical limitations. This work places dissipative Kerr solitons as a leading technology in the millimetre-wave and terahertz-wave field, promising breakthroughs in fundamental and civilian applications.A 300 GHz signal is generated by the combination of a low-noise stimulated Brillouin scattering process, dissipative Kerr soliton comb and optical-to-electrical conversion. A phase noise of −100 dBc Hz−1 is achieved at a Fourier frequency of 10 kHz.

Practical and useful quantum information processing requires substantial improvements with respect to current systems, both in the error rates of basic operations and in scale. The fundamental qualities of individual trapped-ion 1 qubits are promising for long-term systems 2 , but the optics involved in their precise control are a barrier to scaling 3 . Planar-fabricated optics integrated within ion-trap devices can make such systems simultaneously more robust and parallelizable, as suggested by previous work with single ions 4 . Here we use scalable optics co-fabricated with a surface-electrode ion trap to achieve high-fidelity multi-ion quantum logic gates, which are often the limiting elements in building up the precise, large-scale entanglement that is essential to quantum computation. Light is efficiently delivered to a trap chip in a cryogenic environment via direct fibre coupling on multiple channels, eliminating the need for beam alignment into vacuum systems and cryostats and lending robustness to vibrations and beam-pointing drifts. This allows us to perform ground-state laser cooling of ion motion and to implement gates generating two-ion entangled states with fidelities greater than 99.3(2) per cent. This work demonstrates hardware that reduces noise and drifts in sensitive quantum logic, and simultaneously offers a route to practical parallelization for high-fidelity quantum processors 5 . Similar devices may also find applications in atom- and ion-based quantum sensing and timekeeping 6 . Scalable optics co-fabricated with a cryogenic surface-electrode ion trap are used to drive high-fidelity multi-ion quantum logic gates, demonstrating a route to simultaneously scale and reduce errors in quantum processors.

Anthropogenic noise is a pervasive pollutant that decreases environmental quality by disrupting a suite of behaviors vital to perception and communication. However, even within populations of noise-sensitive species, individuals still select breeding sites located within areas exposed to high noise levels, with largely unknown physiological and fitness consequences. We use a study system in the natural gas fields of northern New Mexico to test the prediction that exposure to noise causes glucocorticoid-signaling dysfunction and decreases fitness in a community of secondary cavity-nesting birds. In accordance with these predictions, and across all species, we find strong support for noise exposure decreasing baseline corticosterone in adults and nestlings and, conversely, increasing acute stressor-induced corticosterone in nestlings. We also document fitness consequences with increased noise in the form of reduced hatching success in the western bluebird (Sialia mexicana), the species most likely to nest in noisiest environments. Nestlings of all three species exhibited accelerated growth of both feathers and body size at intermediate noise amplitudes compared with lower or higher amplitudes. Our results are consistent with recent experimental laboratory studies and show that noise functions as a chronic, inescapable stressor. Anthropogenic noise likely impairs environmental risk perception by species relying on acoustic cues and ultimately leads to impacts on fitness. Our work, when taken together with recent efforts to document noise across the landscape, implies potential wide-spread, noise-induced chronic stress coupled with reduced fitness for many species reliant on acoustic cues.

The performance of light microscopes is limited by the stochastic nature of light, which exists in discrete packets of energy known as photons. Randomness in the times that photons are detected introduces shot noise, which fundamentally constrains sensitivity, resolution and speed 1 . Although the long-established solution to this problem is to increase the intensity of the illumination light, this is not always possible when investigating living systems, because bright lasers can severely disturb biological processes 2 – 4 . Theory predicts that biological imaging may be improved without increasing light intensity by using quantum photon correlations 1 , 5 . Here we experimentally show that quantum correlations allow a signal-to-noise ratio beyond the photodamage limit of conventional microscopy. Our microscope is a coherent Raman microscope that offers subwavelength resolution and incorporates bright quantum correlated illumination. The correlations allow imaging of molecular bonds within a cell with a 35 per cent improved signal-to-noise ratio compared with conventional microscopy, corresponding to a 14 per cent improvement in concentration sensitivity. This enables the observation of biological structures that would not otherwise be resolved. Coherent Raman microscopes allow highly selective biomolecular fingerprinting in unlabelled specimens 6 , 7 , but photodamage is a major roadblock for many applications 8 , 9 . By showing that the photodamage limit can be overcome, our work will enable order-of-magnitude improvements in the signal-to-noise ratio and the imaging speed. A quantum microscope obtains signal-to-noise beyond the photodamage limits of conventional microscopy, revealing biological structures within cells that would not otherwise be resolved.

X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. However, ionic migration causes large noise and baseline drift, limiting the detection and imaging performance. Here we largely eliminate the ionic migration in cesium silver bismuth bromide (Cs 2 AgBiBr 6 ) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs 2 AgBiBr 6 enables complete defect passivation and suppressed ionic migration. The detector hence achieves outstanding balanced performance with a signal drifting one order of magnitude lower than all previous studies, low noise (1/ f noise free), a high sensitivity of 250 µC Gy air −1 cm –2 , and a spatial resolution of 4.9 lp mm −1 . The wafer area could be easily scaled up by the isostatic-pressing method, together with the heteroepitaxial passivation, strengthens the competitiveness of Cs 2 AgBiBr 6 -based X-ray detectors as next-generation X-ray imaging flat panels. Ionic migration degrades not only the characteristics of halide perovskite solar cells, but also those of perovskite X-ray detectors. Here Yang et al. employ heteroepitaxial BiOBr to passivate Cs 2 AgBiBr 6 double perovskite, which suppresses ionic migration and obtain high performance X-ray detectors.

Stable skeletons are promising as a compact, concise, and efficient descriptor since they can reflect much critical information about the original object, such as topology, connectivity, etc. However, extracting stable skeletons from images is very challenging since most existing skeleton extraction methods, also named skeletonization methods in some literature, are sensitive to noise, which limits the application of the skeletons in the recognition field. Many denoising methods have been proposed to extract stable skeletons to overcome this problem. However, up to now, there are few review papers to conclude these denoising methods and present their pros and cons. Therefore, In this paper, we survey existing denoising techniques for extracting stable skeletons from images. We first categorize these denoising methods, analyze their core idea, and then present their pros and cons for comparison. In addition, we also offer the potential research direction and possibly challenge.

Optomechanical systems have been exploited in ultrasensitive measurements of force, acceleration and magnetic fields. The fundamental limits for optomechanical sensing have been extensively studied and now well understood—the intrinsic uncertainties of the bosonic optical and mechanical modes, together with backaction noise arising from interactions between the two, dictate the standard quantum limit. Advanced techniques based on non-classical probes, in situ ponderomotive squeezed light and backaction-evading measurements have been developed to overcome the standard quantum limit for individual optomechanical sensors. An alternative, conceptually simpler approach to enhance optomechanical sensing rests on joint measurements taken by multiple sensors. In this configuration, a pathway to overcome the fundamental limits in joint measurements has not been explored. Here we demonstrate that joint force measurements taken with entangled probes on multiple optomechanical sensors can improve the bandwidth in the thermal-noise-dominant regime or the sensitivity in the shot-noise-dominant regime. Moreover, we quantify the overall performance of entangled probes with the sensitivity–bandwidth product and observe a 25% increase compared with that of classical probes. The demonstrated entanglement-enhanced optomechanical sensors would enable new capabilities for inertial navigation, acoustic imaging and searches for new physics.Joint force measurements with entangled optical probes on two optomechanical sensors are demonstrated. The force sensitivity is improved by 40% in the shot-noise-dominant regime. The sensing bandwidth is improved by 20% in the thermal noise limit.

Quantum mechanics dictates that the precision of physical measurements must always comply with certain noise constraints. In the case of interferometric displacement measurements, these restrictions impose a standard quantum limit (SQL), which optimally balances the precision of a measurement with its unwanted backaction1. To go beyond this limit, one must devise more sophisticated measurement techniques, which either ‘evade’ the backaction of the measurement2 or achieve clever cancellation of the unwanted noise at the detector3,4. In the half-century since the SQL was established, systems ranging from LIGO5 to ultracold atoms6 and nanomechanical devices7,8 have pushed displacement measurements towards this limit, and a variety of sub-SQL techniques have been tested in proof-of-principle experiments9–13. However, so far, no experimental system has successfully demonstrated an interferometric displacement measurement with sensitivity (including all relevant noise sources—thermal, backaction and imprecision) below the SQL. Here, we exploit strong quantum correlations in an ultracoherent optomechanical system to demonstrate off-resonant force and displacement sensitivity reaching 1.5 dB below the SQL. This achieves an outstanding goal in mechanical quantum sensing and further enhances the prospects of using such devices for state-of-the-art force sensing applications.Strong quantum correlations in an ultracoherent optomechanical system are used to demonstrate a displacement sensitivity that is below the standard quantum limit.

Measurement has a special role in quantum theory 1 : by collapsing the wavefunction, it can enable phenomena such as teleportation 2 and thereby alter the ‘arrow of time’ that constrains unitary evolution. When integrated in many-body dynamics, measurements can lead to emergent patterns of quantum information in space–time 3 – 10 that go beyond the established paradigms for characterizing phases, either in or out of equilibrium 11 – 13 . For present-day noisy intermediate-scale quantum (NISQ) processors 14 , the experimental realization of such physics can be problematic because of hardware limitations and the stochastic nature of quantum measurement. Here we address these experimental challenges and study measurement-induced quantum information phases on up to 70 superconducting qubits. By leveraging the interchangeability of space and time, we use a duality mapping 9 , 15 – 17 to avoid mid-circuit measurement and access different manifestations of the underlying phases, from entanglement scaling 3 , 4 to measurement-induced teleportation 18 . We obtain finite-sized signatures of a phase transition with a decoding protocol that correlates the experimental measurement with classical simulation data. The phases display remarkably different sensitivity to noise, and we use this disparity to turn an inherent hardware limitation into a useful diagnostic. Our work demonstrates an approach to realizing measurement-induced physics at scales that are at the limits of current NISQ processors. Measurement-induced phases of quantum information have been observed in a system of 70 superconducting qubits.