ABSTRACT Global Navigation Satellite System Reflectometry (GNSS-R) has been successfully applied in fields including ground target detection and imaging. However, the low Power Flux Density (PFD) of signals reflected from the Earth’s surface has long been a critical bottleneck restricting the performance improvement of target detection. The rapid development and large-scale deployment of Low Earth Orbit (LEO) navigation satellites have furnished external illuminators with superior operational performance. The optimization of the quantity and spatial distribution of these transmitters can effectively enhance the accuracy of target state estimation. This paper first analyzes the Signal-to-Noise Ratio (SNR) improvement effect of the LEO-R system from three key dimensions: the orbital altitude of LEO navigation satellites, detection range, coherent time and incoherent time. Furthermore, a moving target state estimation algorithm specifically designed for LEO-R scenarios is proposed. This algorithm extracts the bistatic range and target radial velocity of a single satellite via the Radon-Fourier Transform (RFT), establishes a path difference-based observation model, and adopts the Levenberg-Marquardt (L-M) algorithm to solve the nonlinear least squares problem for precise target position estimation. Subsequently, target velocity is resolved by integrating the position estimation results with a direct physical model. Both simulation and field experimental results validate that the comprehensive performance of the proposed algorithm is significantly superior to that of the conventional Time Difference of Arrival (TDOA) algorithm.

Optical excitation and control of excitonic wavepackets in organic molecules is the basis to energy conversion processes. To gain insights into such processes, it is essential to establish the relationship between the coherence timescales of excitons with the local electronic distribution in the molecules, as well as the influence of intermolecular interactions on exciton dynamics. Here, we demonstrate orbital-resolved imaging of optically induced coherent exciton dynamics in single copper naphthalocyanine (CuNc) molecules, and selective coherent excitation of dark and bright triplet excitons in coupled molecular dimers. Ultrafast photon-induced tunneling current enabled atomic-scale imaging and control of the excitons in resonantly excited molecules by employing excitonic wavepacket interferometry. Our results reveal an ultrafast exciton coherence time of ~ 70 fs in a single molecule, which decreases for the triplet excitons in interacting molecules.

Silicon carbide (SiC) divacancies are attractive candidates for spin-defect qubits possessing long coherence times and optical addressability. The high activation barriers associated with SiC defect formation and motion pose challenges for their study by first-principles molecular dynamics. In this work, we develop and deploy machine learning interatomic potentials (MLIPs) to accelerate defect dynamics simulations while retaining ab initio accuracy. We employ an active learning strategy comprising symmetry-adapted collective variable discovery and enhanced sampling to compile configurationally diverse training data, calculation of energies and forces using density functional theory (DFT), and training of an E(3)-equivariant MLIP based on the Allegro model. The trained MLIP reproduces DFT-level accuracy in defect transition activation free energy barriers, enables the efficient and stable simulation of multidefect 216-atom supercells, and permits an analysis of the temperature dependence of defect thermodynamic stability and formation/annihilation kinetics to propose an optimal annealing temperature to maximally stabilize VV divacancies.

Silicon vacancies (VSi) in 4H-SiC are promising candidates for quantum technologies due to their long spin coherence times and integrability into mature semiconductor platforms. However, conventional CMOS-compatible processing introduces significant photoluminescence noise from passivation layers and crystal damage, degrading color center coherence and excitation line widths. This work evaluates strategies to minimize background noise. Thermally grown oxides with nitrogen monoxide annealing provide excellent low-noise passivation and remain stable during subsequent 600 °C thermal treatments. Furthermore, combining reactive ion etching with atomic layer etching eliminates ion-induced surface damage. Into lateral PIN-diodes, used for stark shift and photoluminescent excitation line width tuning, a selectively etched optical window is integrated. These devices show ideal electrical properties, blocking up to 150 V with leakage current below 10 pA/μm, while significantly enhancing the VSi environment. Single emitters in these PIN-diodes show an increased signal-to-noise ratio of 15 for near-surface and 50 for deeper emitters on both c-plane and a-plane wafers.

Electronic spin superposition states enable nanoscale sensing through their sensitivity to the local environment, yet their sensitivity to vibrational motion also limits their coherence times. In molecular spin systems, chemical tunability and atomic-scale resolution are accompanied by a dense, thermally accessible phonon spectrum that introduces efficient spin relaxation pathways. Despite extensive theoretical work, there is little experimental consensus on which vibrational energies dominate spin relaxation or how molecular structure controls spin-phonon coupling (SPC). We present a fully experimental method to quantify SPC coefficients by combining temperature-dependent vibrational spectra from inelastic neutron scattering with spin relaxation rates measured by electron paramagnetic resonance. We apply this framework to two model S = 1/2 systems, copper(II) phthalocyanine (CuPc) and copper(II) octaethylporphyrin (CuOEP). Two distinct relaxation regimes emerge: below 40 K, weakly coupled lattice modes below 50 cm-1 dominate, whereas above 40 K, optical phonons above ∼185 cm-1 become thermally populated and drive relaxation with SPC coefficients nearly 3 orders of magnitude larger. Structural distortions in CuOEP that break planar symmetry soften the crystal lattice and enhance anharmonic scattering but also raise the energy of stretching modes at the molecular core where the spins reside. This redistributes vibrational energy toward the molecular periphery and out of plane, ultimately reducing SPC relative to CuPc and enabling room-temperature spin coherence in CuOEP. Although our method does not provide mode-specific SPC coefficients, it quantifies contributions from distinct spectral regions and establishes a broadly applicable, fully experimental link between crystal structure, lattice dynamics, and spin relaxation.

The Moon's permanently shadowed regions (PSRs) are among the coldest places in the Solar System and are expected to become key landing sites for upcoming international space agency missions. Their proximity to peaks of perpetual solar power and potential resource richness makes them prime candidates for lunar exploration and future Moon bases. Here, we propose to deploy a passive, ultrastable optical resonator in these regions that will enable laser systems with unprecedented phase-coherence. The unique physical environment of lunar PSRs greatly benefits the construction of a cryogenic monolithic silicon cavity that exhibits low [Formula: see text] thermal noise-limited stability and coherence time exceeding 1 min, more than a decade better than the current best terrestrial system. Such a stable laser will form an enabling infrastructure for quantum technology in space to serve many applications, including establishing a lunar time standard, building long-baseline optical interferometry, distribution of stable optical signals across networks of satellites, testing general relativity and gravitational physics, and forming the backbone for space-based quantum networks.

High-harmonic generation (HHG) has provided groundbreaking insights into nonequilibrium dynamics involving strong light-matter interactions. However, intrinsic quantum effects of condensed matter, such as electronic coherence and its interplay with nuclear degrees of freedom─one of the most fascinating aspects of quantum mechanics─have largely been overlooked. Here, we explore the nuclear quantum effects (NQEs) on electronic coherence in solid-state HHG. Unlike classical nuclei, the strong delocalization of the nuclei caused by zero-point vibrations induces electronic decoherence on an ultrafast (attosecond to femtosecond) timescale through nuclear-electronic entanglement. In this manner, NQEs not only contribute to the ultrafast dephasing of HHG but also suppress the interband electron trajectory and thus switch the dominant mechanism from interband to intraband HHG in solids. This yields measurable signatures in HHG spectroscopy, enabling direct probe of coherence time and nuclear wave packets information in materials.

The relationship between structure and exchange coupling constant J is of interest for the rational design of molecular open-shell systems in the context of molecular magnetism, dynamic nuclear polarization, and quantum information science. However, even for the basic relationship between J and the distance r between two spin centers for the archetypal oligo(p-phenylene) bridge, there are only a few and contradicting experimental and theoretical data. We therefore synthesized a series of six trityl-[(p-phenylene)n=1-5]-trityl biradicals and used Electron Paramagnetic Resonance methods to extract J values in the range from 17.5 MHz to 235 GHz. We find a distance dependence parameter β of 0.11 Å-1 for unsubstituted and 0.67 Å-1 for substituted oligo(p-phenylene) bridges. This places unsubstituted oligo(p-phenylene)-bridges into the spin-conductor regime and highlights the tunability of conductance by substitution, i.e., increase of the dihedral angle between the phenylene units. DFT calculations employing low Fock-exchange fraction functionals exhibit some limitations in reproducing the experimental J value, particularly in the weak coupling regime. Furthermore, biradicals with n = 3 - 5 exhibit spin coherence of 1.2 μs at room temperature in the solution state. These long coherence times, combined with the modular bridge design, position bistrityl systems as promising candidates for applications in quantum information technology.

High-temperature, high-pressure (HPHT) nanodiamond (ND) hosts nitrogen-vacancy (NV) centers, solid-state qubits that enable room-temperature quantum sensing by all-optical magnetometry, electrometry, and thermometry. However, the covalent surface functionalization of nanoscale diamond remains largely limited to carboxylate-based chemistries. Amine termination is particularly attractive because theoretical studies predict suppression of midgap states and extended electron-spin coherence times. Recently, chemical activation of alcohol-terminated NDs to alkyl bromides (ND-Br) using SOBr2 has enabled nucleophilic substitution through a carbocation intermediate, allowing formation of simple amine terminations. Here, we evaluate whether sterically demanding amines can form covalent diamond-nitrogen bonds on ND-Br surfaces. ND-Br was reacted with branched, linear, and cyclic amines, including polyethylenimine, diethylenetriamine, and melamine. X-ray spectroscopies were used to confirm successful and to probe the resulting electronic structure at the diamond-amine interface. These results expand the chemical toolbox for tuning diamond surface dipoles and electron affinity, providing new pathways for engineering nanodiamond surfaces for quantum sensing and photocatalysis applications.

Ordered phases give rise to collective modes and quasiparticles, such as spin waves and magnons emerging from magnetic order. Extending this paradigm to ferroelectrics suggests the existence of polarization waves and their fundamental quanta, ferrons. A coherent ferron-that is, a polarization wave-modulates the magnitude of the electric polarization and is thus an amplitude (Higgs) mode of the ferroelectric order. Here we observe coherent ferrons from the pulsed laser excitation of van der Waals ferroelectrics, NbOI2 and WO2Br2. We demonstrate two complementary manifestations of coherent ferrons: intense narrow-band terahertz emission at the ferroelectric transverse optical phonon frequency, and uniaxial propagation along the polar axis as hyperbolic phonon polaritons with exceptionally long coherence times. These long-lived, uniaxial and dipole-carrying polarization waves may find applications in narrow-band terahertz emission, ferronic information processing and coherent electric control.

A defining characteristic of superconductors is their tendency to expel magnetic fields, yet above a critical threshold, magnetic flux penetrates in discrete quanta carried by Abrikosov vortices1. The superconducting gap is completely suppressed at the vortex core, rendering them dissipative, semi-classical entities that impact applications from high-current-density wires to quantum devices. Material disorder can drive a crossover to vortices that preserve an energy gap at the core2-4, owing to intrinsic5 or emergent granularity on the scale of the coherence length2,6. Although quantum vortex behaviour could emerge in this effective tunnel-junction regime7, and signatures have been observed in diverse systems8-10, coherent manipulation of vortex states has remained elusive. Here we present evidence that vortices trapped in granular superconducting films can behave as two-level systems, exhibiting microsecond-range quantum coherence and energy relaxation times that reach fractions of a millisecond. Using the tools of circuit quantum electrodynamics11, we perform coherent manipulation and quantum non-demolition readout of vortex states in granular aluminium microwave resonators, heralding future directions for quantum information processing, materials characterization and sensing.

Quantitatively mapping temperature within living cells is essential for understanding subcellular biophysical processes; however, existing intracellular quantum sensors such as nanodiamonds with nitrogen-vacancy centers, quantum dots, and fluorescent proteins face limitations in material heterogeneity, cytotoxicity, and thermometric specificity. Here, we present molecular quantum nanosensors (MoQNs) as a next-generation platform for intracellular quantum sensing. MoQNs embed pentacene molecular spin qubits within para-terphenyl nanocrystals coated with Pluronic F-127, yielding a coherent spin system with molecular-level uniformity and long spin coherence times under physiological conditions. By chemically suppressing hyperfine interactions, we enhance spectral resolution and demonstrate spatially resolved absolute temperature sensing inside the cytoplasm and nuclei of cancer cells. MoQNs thus offer a chemically tunable, biologically compatible platform for quantum-level detection of thermal and biochemical states of intracellular environments.

A key advantage of quantum metrology is the ability to surpass the standard quantum limit (SQL) for measurement precision through the use of nonclassical states. However, there is typically little to no improvement in precision with the use of nonclassical states for measurements whose duration exceeds the decoherence time of the underlying quantum states. Measurements aimed at the ultimate possible precision are thus performed almost exclusively with classical states and, therefore, are constrained by the SQL. Here, we demonstrate that by using the phenomenon of subharmonic excitation, in combination with a recently demonstrated technique of Raman excitation of a harmonic oscillator, the frequency of an electric field can be measured at a resolution below the SQL of the corresponding linear generator. With this method we measure a radio-frequency electrical signal with a fractional frequency uncertainty of 0.56 Hz/80 MHz=7×10^{-9}, which to our knowledge is the most precise frequency measurement of a radio-frequency electrical signal using a quantum harmonic oscillator. Because the input states can be classical, the coherence time is not degraded by the enhanced decoherence typically associated with nonclassical states, thereby improving the ultimate achievable precision. While we demonstrate this technique using motional Raman subharmonic excitation of a single ^{40}Ca^{+} ion through engineered Floquet states, this technique is expected to be extendable to other platforms, such as NV centers, solid-state qubits, and neutral atoms, where it can provide metrological gain for sensing across the radio frequency, microwave, and optical domains.

ABSTRACT Flexible photothermal materials made of particulate carbon, metal, polymer, or semiconductors often suffer from interfacial incompatibility, leading to cracking and delamination over prolonged use. These limitations make it difficult for flexible composite materials to simultaneously meet the requirements of long‐term interfacial stability and high photothermal performance. Here we circumvented these persistent challenges by using flexible organic crystals, where the absorber is a structurally homogeneous radical cocrystal and strong light absorption is accomplished by charge transfer (CT) between two molecular components. We cocrystallized electron donor perylene (PE) and acceptor naphthalene diimide (NDI) to prepare mechanically flexible, centimeter‐size cocrystals (PE‐NDI), which demonstrate persistent radical characteristics with a spin coherence time of 2.1 µs. Prominent donor–acceptor interaction (−87.7 kJ mol −1 ) facilitates strong light absorption from 200 to 780 nm, while hydrogen bonds are thought to account for the reversible elastic bending. Excitation at 685 nm yields an extraordinarily high photothermal conversion efficiency of 94%. Integration of PE‐NDI in a thermoelectric generator enabled direct solar energy harvesting via a photo‐thermo‐electric conversion sequence, demonstrating the potential of flexible cocrystals for renewable energy harvesting. This work highlights the untapped potential of mechanically compliant organic crystals as flexible, single‐component, lightweight photothermal materials.

Flexible photothermal materials made of particulate carbon, metal, polymer, or semiconductors often suffer from interfacial incompatibility, leading to cracking and delamination over prolonged use. These limitations make it difficult for flexible composite materials to simultaneously meet the requirements of long-term interfacial stability and high photothermal performance. Here we circumvented these persistent challenges by using flexible organic crystals, where the absorber is a structurally homogeneous radical cocrystal and strong light absorption is accomplished by charge transfer (CT) between two molecular components. We cocrystallized electron donor perylene (PE) and acceptor naphthalene diimide (NDI) to prepare mechanically flexible, centimeter-size cocrystals (PE-NDI), which demonstrate persistent radical characteristics with a spin coherence time of 2.1 µs. Prominent donor-acceptor interaction (-87.7kJ mol-1) facilitates strong light absorption from 200 to 780nm, while hydrogen bonds are thought to account for the reversible elastic bending. Excitation at 685nm yields an extraordinarily high photothermal conversion efficiency of 94%. Integration of PE-NDI in a thermoelectric generator enabled direct solar energy harvesting via a photo-thermo-electric conversion sequence, demonstrating the potential of flexible cocrystals for renewable energy harvesting. This work highlights the untapped potential of mechanically compliant organic crystals as flexible, single-component, lightweight photothermal materials.

Molecular polaritons, formed by coupling molecular excitons with cavity photons, offer a promising platform for exploring quantum phenomena. A key challenge is understanding how these hybrid states maintain coherence in the presence of environmental vibrations. Here, we show theoretically that collective coupling of many molecular excitons in a cavity can protect polariton coherence from phonon-induced decoherence. Under realistic conditions, the coherence time can extend up to 200 fs at room temperature, compared with 15 fs for typical molecular systems. Simulations of two-dimensional electronic spectra reveal prolonged oscillations between upper and lower polariton states, and reduced vibrational coupling as indicated by changes in the nodal line slope of the lower polariton peak. These findings provide guidance for experimental efforts to realize long-lived polaritons, such as coupling CdSe nanoplatelets to optical cavities.

The stability of motional-mode frequency is essential for realizing high-fidelity quantum gates in trapped-ion quantum computing. While broadband Gaussian noise has been extensively studied and mitigated using pulse shaping techniques, the impact of coherent periodic noise has remained largely unexplored. Here we report a systematic investigation of 60-Hz power-line noise and its effect on the secular frequencies of a single [Formula: see text] ion. Using spin-echo Ramsey spectroscopy, we characterize the amplitude and phase of the resulting secular-frequency modulation and validate this characterization via passive phase correction of the Ramsey sequence. Building on this, we implement a cancellation scheme by injecting a compensation tone into the set-point of a PI controller that stabilizes the trap RF drive amplitude. A phasor-fitting procedure optimizes the amplitude and phase of the compensation signal, enabling near-complete suppression of the 60-Hz component. With the cancellation applied, the coherence time of a radial motional mode is extended from approximately 10 ms to 35 ms, consistent with the limit set by motional heating. Our results provide both a clear characterization of periodic motional-mode noise and a practical framework for its suppression in trapped-ion quantum computing platforms.

We report electrical spin-state readout and coherent control of an ensemble (∼540) of silicon vacancies (VSi-) in a silicon carbide-on-insulator (SiCOI) platform, with excitation wavelengths from 780 to 990 nm, demonstrating for the first time spin-state readout well beyond the zero phonon line of the V2 VSi-. By implementing photoelectrical detection of magnetic resonance in thin-film SiCOI, we merge a scalable spin readout technique requiring no collection optics, together with a promising platform for future scalable and CMOS-compatible integrated photonics. Furthermore, we provide a comparison of optical and electrical readout between bulk silicon carbide (SiC) and thin-film SiCOI, revealing that our thin-film processing has a measured T2 coherence time of ≈7 μs, similar to that in the bulk SiC. These results extend the capabilities of SiCOI toward electronic and spin-based devices for scalable quantum technologies over a wide range of excitation wavelengths.

Diamond nitrogen–vacancy (NV) centers possess long coherence times and stable fluorescence emission, and have therefore attracted widespread attention in fields such as quantum communication, biological fluorescence labeling, and precision sensing. However, the high refractive index of diamond causes most of the fluorescence from the color centers to be internally reflected, resulting in low fluorescence collection efficiency. To improve the utilization efficiency of fluorescence from diamond color centers, this work proposes a low‐cost and controllable method for fabricating nanocone array structures. By depositing a SiO 2 array mask, the effects of etching power and bias power on the morphologies of both the mask and the diamond were investigated. Subsequently, the regulatory mechanism of the O 2 /CF 4 mixed‐gas ratio on the etching behaviors of the mask and diamond was explored, and it was found that an increased CF 4 proportion is beneficial for reducing the cone angle of the nanocone structures. Optical characterization reveals that the fabricated diamond cone structure with a cone angle of 73° exhibits an approximately twofold increase in transmittance, while simultaneously enhancing the fluorescence intensities of both NV − and SiV − color centers. Compared with a diamond thin film, the fluorescence enhancement reaches 12.2 times for NV − centers and 11.7 times for SiV − centers. Finite‐difference time‐domain (FDTD) simulations further demonstrate that the cone structure can concentrate photons, thereby effectively improving the fluorescence collection efficiency of color centers. This work provides a feasible approach for the low‐cost fabrication of quantum sensing devices and for enhancing the sensitivity of quantum detection.

The utilization of quantum effects by nature to enhance photosynthetic efficiency has emerged as a subject of intense scientific inquiry. However, fundamental questions remain unresolved, most notably, whether coherent energy transfer occurs in the primary photochemical events. This featured article summarizes recent work from our group and collaborators, addressing several manifestations of biological quantum effects in photosynthesis across varied spatial scales. These include: (1) Coherent energy transfer in allophycocyanin (inter-pigment distance of 21 Å) and phycoerythrin 545 (15 Å). An exciton-vibrational coherence time of up to 500 fs and a 220 fs coherent energy transfer time have been observed in allophycocyanin. In contrast, in the structurally similar phycocyanin 620, which possesses an identical pigment pair and separation distance, energy transfer follows an incoherent way with a time constant of 460 fs. (2) Quantum switch in the light-harvesting complex of photosystem II of higher plants, which is driven by a dynamical protein structure. The antenna reversibly regulates light harvesting (Förster energy transfer, classical) and excess energy dissipation (Dexter energy transfer, quantum mechanical) states in response to dynamic changes in sunlight intensity. This switch is achieved by dynamic modulation of the distance between the main quenching pair, lutein 1 and chlorophyll a 612 (∼5.6 to 6 Å). (3) Macroscale quantum design in membrane architecture. The optimal size of intracytoplasmic membrane vesicles is regulated by quantum design principles in the LH2 structure, where the structural robustness and excitonic coherence of LH2 are preserved only within an evolutionarily optimized vesicle size range (50-80 nm).