Search Results (78)

The Boltzmann–Loschmidt dispute of 1876 questioned the possibility of a statistical irreversible description by time-reversible classical equations of motion of atoms. Here we show analytically and numerically that the quantum chaos diffusion of cold atoms, or ions, in a harmonic trap and pulsed optical lattice can be inverted back in time with up to 100% efficiency. This is in sharp contrast to classical evolution, where exponentially small errors break time reversibility. We argue that the existing experimental skills allow highlighting the Boltzmann–Loschmidt dispute from a quantum perspective. Full article

Atmospheric aerosols modulate Earth’s radiation balance through direct effects and through their role as cloud condensation nuclei (CCN), contributing to variability in near-surface temperature (NST). Galactic cosmic rays (GCRs) further influence aerosol–cloud interactions by enhancing particle formation and growth, but combined aerosol optical depth (AOD)–GCR effects on NST remain poorly constrained across climates. Using satellite and reanalysis data, we examine joint influences on NST anomalies at three neutron-monitoring stations, Oulu, Newark, and Hermanus, during 2000–2022. The sites share similar geomagnetic cutoffs but contrasting climates, enabling separation of ionization from geomagnetic shielding. Multiple linear regression (MLR) captures AOD effects and their modulation by GCR flux. Adding an interaction term (AOD × GCR) improves fit, raising adjusted R² from 0.22→0.31 (Oulu), 0.37→0.52 (Newark), and 0.69→0.78 (Hermanus). ECMWF reanalysis shows hydrophilic organic matter aerosol (OMA) dominates (0.19, 0.29, 0.41 µg kg⁻¹ at Oulu, Newark and Hermanus), with sulphate elevated at Oulu/Newark and coarse sea salt at Hermanus. Elevated OMA and sulphate at Oulu/Newark imply GCR-enhanced fine CCN and cooling, whereas humid, sea-salt-rich Hermanus favors ion-mediated growth of larger hygroscopic particles that increase longwave trapping and warming. Findings provide site-specific evidence that GCR ionization modulates aerosol processes and contributes to regional NST variability, informing improved parameterizations in climate models. Full article

We reviewand update schemes for different measurements using STA-mediated guided interferometry with a single trapped particle. STA stands for “shortcuts to adiabaticity”, a set of techniques to achieve the results of adiabatic dynamics in shorter times. In the first scheme we presented a protocol aimed at detecting weak unknown forces. It consisted of a single ion trapped in a harmonic potential and driven by time-and-spin-dependent forces generated via off-resonant lasers. Our approach provided stability and the independence of the results on the motional states for the small-oscillations regime. We could, also, design faster-than-adiabatic processes with sensitivity control. However, it required a rotation of the trapping potential at the moment the experiment starts. A much more practical and broadly applicable design was then developed, where no rotation is involved. Here, a single atom is driven by two moving spin-dependent trapping potentials where we guide the arms of the interferometer via shortcuts to adiabatic paths. In this paper, in addition to a brief review of these two previous proposals, we revisit the first scheme and present a new protocol where the spin-dependent driving force is generated via a “shaken” optical lattice. This opens the possibility for additional interferometric measurements beyond an unknown force, for example, the mass of the trapped ion, while still preserving the advantages of the previously proposed method. Full article

Quantum walks (QWs) represent pillars of quantum dynamics and information processing. They provide a powerful framework for simulating quantum transport, designing search algorithms, and enabling universal quantum computation. Several physical platforms have been employed for their implementation, such as trapped atoms and ions, nuclear magnetic resonance systems, and photonic quantum architectures either in bulk optics or waveguide structures and fiber loop networks. Here we focus on the most promising and versatile approach, which is photonic integrated circuits. In this work, we review how the employment of this versatile experimental platform has allowed exploring several phenomena related to QW-based protocols, such as evolution in the presence of different kinds of noise. In this landscape, to the best of our knowledge, few examples report on the introduction of absorbing centers and their effects on the coherence of the dynamics. Here we present and discuss the results related to the absorbing boundaries in QWs, obtained through theoretical simulations and experiments conducted with the universal photonic quantum processors realized by QuiX Quantum. We analyze how localized absorption along one lattice edge affects the walker dynamics, depending on both the leakage probability and the initial injection site. Our results suggest that the presence of controlled losses modifies interference patterns and coherence without fully destroying quantum features and providing an effective resource for engineering on-chip QWs and simulating open quantum systems. Full article

Metal–organic frameworks (MOFs), particularly Zeolitic Imidazolate Framework-8 (ZIF-8), are promising photocatalysts; however, their practical application is limited by a wide band gap (~3.85 eV), which restricts light absorption mainly to the ultraviolet region. This limitation was addressed by synthesizing a series of cobalt-doped ZIF-8 materials, Co(x)ZIF-8 (x = 0, 2.5, 5, 7.5, and 10 wt%), using a cost-effective aqueous synthesis route. Structural and compositional analyses using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) confirmed the formation of phase-pure ZIF-8 topology, with no significant change in nanoparticle morphology upon the partial substitution of Zn²⁺ by Co²⁺ ions within the framework. UV–Vis diffuse reflectance and Tauc plot analysis revealed a systematic and substantial reduction in the optical band gap (Eg) with increasing Co content, indicating enhanced visible-light absorption capability. All Co(x)ZIF-8 samples exhibited superior photocatalytic activity compared to pristine ZIF-8 under light irradiation. Among them, Co(2.5)ZIF-8 displayed the highest apparent reaction rate constant for pollutant degradation, while Co(5)ZIF-8 achieved the highest overall degradation efficiency (~87%) after 40 min. The enhanced photocatalytic performance is attributed to the synergistic effects of band-gap narrowing and the presence of Co²⁺ ions, which act as effective charge-trapping centers and suppress electron–hole recombination. Electrochemical measurements further demonstrated that Co(5)ZIF-8 exhibits the highest current density (most negative J) at large negative potentials (e.g., J ≈ −0.105 A cm⁻² at E = −2.0 V), indicating superior intrinsic catalytic activity. These findings highlight cobalt-doped ZIF-8 as a highly tunable and efficient photocatalyst with strong potential for environmental remediation applications. Full article

Through finite-element simulation, the axial potential distribution of the ion trap is analyzed. The effects of the central hole diameter of the end cap and the spacing between the two end caps on the axial geometric parameters of the ion trap are investigated. Based on these findings, a set of linear Paul traps is designed by selecting suitable end caps and quadrupoles. Stable trapping of calcium ions (Ca⁺) is successfully achieved, and these ions are subsequently laser-cooled into ionic Coulomb crystals. In the experiment, secular motion excitation of the Ca⁺ ion Coulomb crystal is performed, yielding an axial geometric parameter of 0.115(1) for the ion trap. This value aligns well with the simulation result of 0.114(2). The precise determination of the axial geometric parameter provides a solid foundation for subsequent high-precision optical or mass spectrometry measurements. Full article

Optical synaptic transistors employing polymer dielectrics have emerged as promising building blocks for neuromorphic computing due to their low power consumption and rich photo-induced memory behaviors. While extensive experimental studies have demonstrated various synaptic functions, a unified physical understanding of the coupled charge trapping and ionic polarization processes governing device dynamics remains incomplete. In this work, we develop a unified physical model to investigate optical synaptic behaviors in polymer-based transistors with oxide interlayers. The model explicitly describes the time-dependent evolution of photo-induced charge trapping at the semiconductor–dielectric interface and ionic polarization within the polymer dielectric, which jointly modulate the effective threshold voltage of the transistor channel. Based on this framework, key synaptic functions including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), and pulse-dependent potentiation are quantitatively reproduced. The model further reveals how dielectric structure and trapping strength govern the transition between short-term and long-term plasticity. This study provides a physically intuitive and experimentally relevant modeling framework for understanding optical synaptic transistors, offering guidance for the rational design and optimization of polymer-based neuromorphic devices. Although simplified, the proposed model captures the essential physics governing optical synaptic behaviors and provides a general framework applicable to a wide class of ion–electronic neuromorphic devices. Experimental measurements are used as physically motivated proxies to validate the multi-timescale structure of the model rather than direct numerical fitting. Full article

The ²²⁹Th nuclear clock, based on a low-energy nuclear transition, has attracted significant interest as a next-generation time and frequency standard. It is expected to surpass current leading optical atomic clocks in performance. Because nuclear transitions are naturally isolated from external electromagnetic fields, their sensitivity to blackbody radiation and environmental noise is much lower than that of electronic transitions. This gives the nuclear clock a unique advantage in both stability and accuracy. This paper reviews the current progress in nuclear clock research, focusing on the physical properties of the ²²⁹Th isomer, the operating principles, and the primary implementation methods of the nuclear clock. Comparing key technical approaches, specifically trapped ions and thorium-doped crystals, and introducing the VUV frequency comb technology used to drive the nuclear transition. Finally, we provide an outlook on the future development of the field. Full article

Rare-earth fluoride nanocrystals have emerged as promising scintillator materials due to their excellent optical properties, environmental stability, and ease of fabrication into flexible screens. However, their practical application is often hindered by persistent afterglow, a phenomenon caused by deep trap states that capture and slowly release charge carriers after X-ray excitation, which leads to signal overlap and image artifacts in dynamic imaging scenarios. This study addresses this critical challenge by developing Ce³⁺/Tb³⁺ co-doped NaLuF₄ nanoscintillators with suppressed afterglow. By introducing Ce³⁺ions as dopants into the Tb³⁺-activated NaLuF₄ host, we successfully quenched the characteristic long afterglow without compromising the intrinsic radioluminescence efficiency of the Tb³⁺ centers. The optimized nanocrystals were subsequently incorporated into a poly (vinyl alcohol) matrix to fabricate transparent, high-loading composite scintillator films. The resulting films exhibit negligible afterglow, maintain high spatial resolution, and demonstrate excellent radiation stability. This work presents an effective strategy for suppressing afterglow in rare-earth fluoride scintillators through targeted ion doping, which paves the way for their application in real-time, high-quality X-ray imaging technologies such as medical diagnostics and industrial inspection. Full article

Lead halide perovskites, exemplified by methylammonium (MA) lead iodide (MAPbI₃), combine strong optical absorption, long carrier diffusion lengths, and defect-tolerant electronic structure with facile processing, making them attractive for photovoltaics and radiation detection. Yet, their behavior under electron irradiation remains insufficiently understood, limiting deployment in space and dosimetry contexts. Here, we employ Monte Carlo simulations (Geant4) to model electron interactions with MAPbI₃ across energies from 0.1 to 100 MeV and absorber thicknesses from 10 μm to 1 cm. We quantify deposited energy, event statistics, energy per interaction, non-ionizing energy loss, and dominant radiation effects. The results reveal strong thickness-dependent regimes: thin photovoltaic-type layers (~hundreds of nanometers) are largely transparent to MeV electrons, minimizing bulk damage but allowing localized ionization, exciton self-trapping, and photoexcitation-driven ion migration. Although localized excitations can temporarily improve carrier collection under short-term exposure, their cumulative effect drives ionic rearrangement and defect growth, ultimately reducing device stability. In contrast, thicker detector-type films (10–100 μm) sustain multiple scattering and ionization cascades, enhancing sensitivity but accelerating defect accumulation. At centimeter scales, energy deposition saturates, enabling bulk-like absorption for high-flux dosimetry. Overall, electron irradiation in MAPbI₃ is dominated by electronic excitation rather than ballistic displacements, underscoring the need to optimize thickness and composition to balance efficiency, sensitivity, and durability. Full article

Centro Español de Metrología (CEM) is developing a quantum frequency standard based on trapped calcium ions, marking its entry into the landscape of the second quantum revolution. Optical frequency standards offer unprecedented precision by referencing atomic transitions that are fundamentally stable and immune to environmental drift. However, the challenge of developing such a system from scratch is unaffordable for a medium-sized National Metrology Institute (NMI), which seems to limit the ability of an institute such as CEM to contribute to this field of research. To overcome this, CEM has adopted a hybrid strategy, combining commercially available components with custom integration to accelerate deployment. This paper defines and implements an architecture adapted to the constraints of a medium-size NMI, where the main contribution is the systematic design, selection, and interconnection of the subsystems required to realize this standard. The rationale behind the system design is presented, detailing the integration of key elements for ion trapping, laser stabilization, frequency measurement, and system control. Current progress, ongoing developments, and future research directions are outlined, establishing the foundation for spectroscopic measurements and uncertainty evaluation. The project represents a strategic step toward strengthening national capabilities in quantum metrology for a medium-sized NMI. Full article

In this study, radiation damage in BaFBr and BaF₂ crystals irradiated with 147 MeV ⁸⁴Kr ions up to fluences of (10¹⁰–10¹⁴) ions/cm² was investigated using X-ray excited optical luminescence (XEOL) and pulsed cathodoluminescence (PCL). The effect of oxygen impurities present in the studied crystals was also considered. XEOL spectra revealed bands associated with oxygen impurities occupying halide sites, as well as luminescence bands with maxima at approximately 2.81 eV, 3.7–4 eV, and 2.3 eV. The luminescence at 2.81 eV can be attributed to the recombination of electrons released during X-ray irradiation with holes trapped at specific sites (Type I, PL). The observed highly energetic luminescence is most likely due to perturbed exciton. Such a perturbed exciton can be formed in the configuration F + V_k (${\mathrm{Br}}_2^{-}$) in the presence of the neighboring impurity ion $O^{2-}$. Oxygen impurities play an important role in the formation mechanisms of these centers. High radiation doses lead to crystal degradation. Excitation by a high-power electron pulse induces excitonic luminescence near the oxygen impurity at 4.2 eV. A distinctive feature of the 4.2 eV emission band is its strong intensity at high temperatures. In the decay kinetics of the PCL spectra, a fast component in the nanosecond range dominates, which remains independent of fluence in BaFBr and BaF₂ crystals irradiated with krypton ions. Full article

Zero-dimensional (0D) rare-earth-based metal halides show great potential in photonic and optoelectronic applications owing to their high stability, strong exciton confinement, and tunable energy levels. However, the weak absorption and narrow 4f-4f transitions of rare-earth ions limit their performance. To address this, a series of Sb³⁺-doped Cs₃LnCl₆ (Ln: Yb, La, Eu, Ho, Ce, Er, Tb, Sm, Y) nanocrystals were synthesized via a hot-injection method to study the role of Sb³⁺ doping. Sb³⁺ incorporation induces strong broadband self-trapped exciton (STE) emission from Jahn–Teller-distorted [SbCl₆]³⁻ units and enables efficient energy transfer from STEs to rare-earth ions. As a result, the photoluminescence intensity and spectral tunability are improved, accompanied by bandgap narrowing and enhanced light absorption. Different lanthanide hosts exhibit distinct luminescence behaviors: La-based materials show dominant STE emission, while Tb-, Er-, Yb-, Ho-, and Sm-based systems display STE-mediated energy transfer and enhanced f-f emission. In Eu- and Ce-based hosts, unique mechanisms involving Eu²⁺/Eu³⁺ conversion and Ce³⁺ → STE energy transfer are observed. Moreover, composition-dependent emissions in Sb³⁺-doped Cs₃Tb/EuCl₆ enable a dual-mode color and spectral encoding strategy for optical anti-counterfeiting. This study highlights the versatile role of Sb³⁺ in tuning electronic structures and energy transfer, offering new insights for designing high-performance rare-earth halide materials for advanced optoelectronic applications. Full article

Microwave-driven quantum logic gates in trapped-ion systems offer a scalable and laser-free alternative to optical control, with the potential for robust integration into surface-electrode trap architectures. In this work, we present a systematic design guideline for planar ion traps optimized for fast two-qubit microwave gates using chip-integrated conductors. We investigate two electrode configurations, one employing a single microwave line for driving $\sigma$ transitions, and another with two symmetric lines for $\pi$ transitions. Through finite-element simulations, we analyze ion height, magnetic field gradients, heating effects, and gate durations under realistic cryogenic conditions. Our results show that both configurations can achieve two-qubit gate times in the order of 10 μs for ${}^9\mathrm{Be}^{\mathrm{+}}$ and ${}^{40}\mathrm{Ca}^{\mathrm{+}}$ ions. Full article

Current temperature sensors require regular recalibration to maintain reliable temperature measurement. Photonic/quantum-based approaches have the potential to radically change the practice of thermometry through provision of in situ traceability, potentially through practical primary thermometry, without the need for sensor recalibration. This article gives an overview of the European Partnership in Metrology (EPM) project: Photonic and quantum sensors for practical integrated primary thermometry (PhoQuS-T), which aims to develop sensors based on photonic ring resonators and optomechanical resonators for robust, small-scale, integrated, and wide-range temperature measurement. The different phases of the project will be presented. The development of the integrated optical practical primary thermometer operating from 4 K to 500 K will be reached by a combination of different sensing techniques: with the optomechanical sensor, quantum thermometry below 10 K will provide a quantum reference for the optical noise thermometry (operating in the range 4 K to 300 K), whilst using the high-resolution photonic (ring resonator) sensor the temperature range to be extended from 80 K to 500 K. The important issues of robust fibre-to-chip coupling will be addressed, and application case studies of the developed sensors in ion-trap monitoring and quantum-based pressure standards will be discussed. Full article