Quantum Effects Research Articles

Nanobioprospecting of photoautotrophs for the fabrication of quantum dots: mechanism and applications.

Quantum dots (QDs), also known as nanoparticle-based fluorescent probes, are luminescent semiconductor particles with a size range of 2-20nm. The unique optical and electronic capabilities of QDs have led to expanded applications in several fields such as optoelectronics, transistors, sensors, photodetection, catalysis, and medicine. The distinct quantum effects of nanocrystals can be controlled by changing their sizes and shapes using a variety of top-down and bottom-up tactics. QDs were traditionally fabricated using complex, expensive, toxic, and aggressive chemical techniques, which limited their application in a variety of disciplines. A unique approach for the biosynthesis of nanomaterials has been devised, which employs living organisms in the synthesis process and adheres to green chemistry principles. Biogenic QDs have favorable physicochemical features, biocompatibility, and fewer cytotoxic effects as a result of using natural biomolecules and enzymatic processes for mineralization, detoxification, and nucleation of metals and nonmetals to synthesize QDs. This is the first comprehensive review of its kind that highlights the synthesis of several doped and undoped QDs, including graphene QDs, carbon dots, silicon QDs, N/S-CDs, silver-CDs, cadmium-selenium QDs, and zinc oxide QDs, exclusively using photoautotrophic algae and plants. The different plausible mechanisms behind phyco- and phyto-fabrication of QDs are also discussed in detail along with their applications that include detection of organic and inorganic compounds, degradation of hazardous dyes, free radical scavenging, antimicrobial activity, cytotoxicity and bioimaging. Thus, this review aims to give valuable insights for the rational fabrication of photoluminescent nanomaterials with tunable structural and functional properties.

NANOTECHNOLOGY IN DENTISTRY: DIAGNOSTICS AND TREATMENT

The rapid development of nanotechnology in medicine and dentistry has led to an exponential increase in the scope of research in this area. Aspects of nanotechnology that have already brought benefits include advanced drug delivery platforms, molecular imaging, and the development of treatment materials in dental practice. The aim of the research. To investigate the current possibilities of using nanotechnology in dentistry for diagnosis and treatment. Materials and methods of the research. The materials were used scientific publications by authors conducting their scientific and practical research in the field of dentistry and nanotechnology. The search was conducted in the scientometric databases PubMed, Scopus, Web of Science, Google Scholar using the terms “nanoparticles”, “oral cavity”, “nanomaterials”, “nanodentistry”, “diseases”, “biomaterials”, “treatment”, “diagnostics”. The research was conducted using such scientific methods as theoretical generalization and grouping, formalization, analysis, synthesis, and generalization of the results. The search resulted in the selection of publications for the period 2019-2024 that studied nanotechnology and its application in dental practice in diagnosis and treatment and will be discussed in this review. Results. The article shows a unique feature of nanotechnology, which is that the properties of a material at the nanoscale can differ from those at the macro level. This can be explained by two reasons: first, nanomaterials have a large surface area to volume ratio, which causes their high reactivity and, accordingly, affects their mechanical and electrical properties. Secondly, at the nanoscale, quantum effects dominate the material's behavior, giving rise to interesting observations of its electromagnetic and optical properties. Knowing the beneficial aspects of nanomedicine, scientists are trying to use nanotechnology to diagnose, treat and prevent dental diseases. Nanotechnology is used for sensitive medical procedures. They also demonstrate successful and useful applications for precise pain management, tooth restoration, and reduction of tooth hypersensitivity. Nanomaterials can plug open dentinal tubules, improving patient comfort and overall oral health. Orthodontic therapy has also been revolutionized by nanomaterials with shape memory properties, which enables faster and more efficient tooth movement. The development of revolutionary products and therapeutic alternatives is supported by ongoing research efforts, enabling the creation of dental implants, fillings and prostheses that closely mimic the characteristics of natural teeth. Nano-delivery systems are being developed to deliver drugs precisely into the oral cavity, providing optimal therapeutic outcomes with minimal side effects. This review highlights the multifaceted aspects of nanomedicine and how nanotechnology is proving to be useful in the diagnosis and treatment of dental diseases. The integration of nanotechnology into dentistry represents a groundbreaking evolution that goes beyond conventional oral care methods, allowing for the development of innovative diagnostic methods and improved oral health. Prospects for further research. Nanotechnology has revolutionized dentistry by changing the way oral care is conceptualized, delivered, and maintained. To develop effective methods for the diagnosis and treatment of dental diseases, it is necessary to continue research on the optimization of the mechanical properties and cytotoxicity of dental composite materials based on nanotechnology.

Quantum topological data analysis via the estimation of the density of states

We develop a quantum topological data analysis (QTDA) protocol based on the estimation of the density of states (DOS) of the combinatorial Laplacian. Computing topological features of graphs and simplicial complexes is crucial for analyzing data sets and building explainable artificial intelligence solutions. This task becomes computationally hard for simplicial complexes with over 60 vertices and high-degree topological features due to a combinatorial scaling. We propose to approach the task by embedding underlying hypergraphs as effective quantum Hamiltonians and evaluating their density of states from the time evolution. Specifically, we compose propagators as quantum circuits using the Cartan decomposition of effective Hamiltonians and sample overlaps of time-evolved states using multifidelity protocols. Next we develop various postprocessing routines and implement a Fourier-like transform to recover the rank (and kernel) of Hamiltonians. This enables us to estimate the Betti numbers, revealing the topological features of simplicial complexes. We test our protocol on noiseless and noisy quantum simulators and run examples on IBM quantum processors. We observe the resilience of the proposed QTDA approach to real-hardware noise even in the absence of error mitigation, showing the promise for near-term device implementations and highlighting the utility of global DOS-based estimators. Published by the American Physical Society 2024

Decoherence in electron transport: back-scattering, effect on interference and rectification

Decoherence is an undesirable, but ubiquitous phenomenon in quantum systems. Here, we study the effect of partial decoherence, induced via a Büttiker probe, on two-terminal electronic transport across one-dimensional quantum wires and rings, in both the linear and non-linear regimes. We find that dephasing causes backscattering when introduced locally in a ballistic channel. Further, we find that decoherence results in rectification when inversion is broken in the two-terminal transport set-up by a combination of a local dephasing centre and a static impurity. Interestingly, the rectification strength and even its direction varies strongly with the relative distance between the probe and the scatterer. We further analyze how decoherence affects characteristic quantum effects in electronic transport, such as, Fabry-Pérot oscillations in double-barrier setups, and Aharonov–Bohm interference in one-dimensional rings, and find that the amplitude of oscillations in conductance is reduced by decoherence.

Nanomaterials in bacterial detection: current trends and future outlook

Contamination by pathogenic bacteria represents a severe risk to public health and well-being. We outlined current approaches to detecting and sensing harmful bacteria by integrating recognition elements with nanomaterials (NMs) in this study. Nanomaterials have emerged as a transformative technology for bacterial detection due to their unique physicochemical properties, including high surface area, quantum effects, and enhanced reactivity. This review highlights the current trends in the application of various nanomaterials, such as gold nanoparticles, carbon nanotubes, and quantum dots, in the detection of bacterial pathogens. These materials enable the development of selective, and rapid detection methods through mechanisms like surface plasmon resonance, electrochemical sensing, and fluorescence. Furthermore, integrating nanomaterials with microfluidic devices and biosensors is discussed, showcasing advancements in point-of-care diagnostics. Challenges such as stability, reproducibility, and potential toxicity of nanomaterials are addressed, alongside regulatory considerations. The future outlook emphasizes the potential of emerging nanomaterials, such as graphene and metal-organic frameworks, to revolutionize bacterial detection. This review aims to enhance the scalability, cost-effectiveness, and environmental sustainability of these technologies, paving the way for widespread clinical and environmental applications.

Refined prediction of thermal transport performance in amorphous silica

Thermal transport in amorphous silica (a-SiO2) and silica aerogel is critically important for thermal protection and microelectronics applications. However, notable disparities exist between the predicted and measured thermal conductivity of a-SiO2. Inspired by the dual-phonon theory proposed by Luo et al. [Nat. Commun. 2020, 11, 2554] for crystalline materials, this work introduces a dual-diffuson transport method for amorphous materials. The criterion based on the thermal diffusivity is employed to differentiate between normal diffusons and phonon-like diffusons. Herein, the thermal conductivity of a-SiO2 is investigated by combining a modified Allen-Feldman (AF) theory with the dual-diffuson transport method. The present method is validated well by the measurement using the transient plane source (TPS) method. In addition, the results indicate that normal diffusons primarily govern the thermal transport in a-SiO2, with only a minor contribution from phonon-like diffusons. The temperature dependence of specific heat capacity and mode linewidth contributes to the positive temperature-dependent thermal conductivity. The quantum effect of specific heat capacity is the primary influencing factor in the temperature range of 100–1000 K, while the mode linewidth becomes dominant at higher temperatures. Finally, a theoretical framework for predicting the solid thermal conductivity of silica aerogel is introduced by including the temperature effect on the inherent thermophysical properties of the backbone. This work uncovers the physical mechanisms underlying temperature-dependent thermal transport in a-SiO2 and silica aerogels.

Dimensionless fluctuations balance applied to statistics and quantum physics

This work presents a new method called Dimensionless Fluctuation Balance (DFB), which makes it possible to obtain distributions as solutions of Partial Differential Equations (PDEs). In the first case study, DFB was applied to obtain the Boltzmann PDE, whose solution is a distribution for Boltzmann gas. Following, the Planck photon gas in the Radiation Law, Fermi–Dirac, and Bose–Einstein distributions were also verified as solutions to the Boltzmann PDE. The first case study demonstrates the importance of the Boltzmann PDE and the DFB method, both introduced in this paper. In the second case study, DFB is applied to thermal and entropy energies, naturally resulting in a PDE of Boltzmann’s entropy law. Finally, in the third case study, quantum effects were considered. So, when applying DFB with Heisenberg uncertainty relations, a Schrödinger case PDE for free particles and its solution were obtained. This allows for the determination of operators linked to Hamiltonian formalism, which is one way to obtain the Schrödinger equation. These results suggest a wide range of applications for this methodology, including Statistical Physics, Schrödinger’s Quantum Mechanics, Thin Films, New Materials Modeling, and Theoretical Physics.

Bose Metals, from Prediction to Realization.

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid 1990s, showing that they arise due to topological quantum effects. The observation of Bose metals in perfectly regular Josephson junction arrays fully confirms our prediction and rules out alternative models based on disorder. Here, we review the basic mechanism leading to Bose metals. The key points are that the relevant vortices in granular superconductors are core-less, mobile XY vortices which can tunnel through the system due to quantum phase slips, that there is no charge-phase commutation relation preventing such vortices from being simultaneously out of condensate with charges, and that out-of-condensate charges and vortices are subject to topological mutual statistics interactions, a quantum effect that dominates at low temperatures. These repulsive mutual statistics interactions are sufficient to increase the energy of the Cooper pairs and lift them out of condensate. The result is a topological ground state in which charge conduction along edges and vortex movement across them organize themselves so as to generate the observed metallic saturation at low temperatures. This state is known today as a bosonic topological insulator.

Hierarchical Equations of Motion for Quantum Chemical Dynamics: Recent Methodology Developments and Applications.

ConspectusQuantum effects are critical to understanding many chemical dynamical processes in condensed phases, where interactions between molecules and their environment are usually strong and non-Markovian. In this Account, we review recent progress from our group in development and application of the hierarchical equations of motion (HEOM) method, highlighting its ability to address some challenging problems in quantum chemical dynamics.In the HEOM method, the bath degrees of freedom are represented using effective modes from exponential decomposition of the bath correlation function. Complex spectral densities and low temperature simulations often require a larger number of modes, making the simulations very expensive. Recent advances, such as the barycentric spectral decomposition (BSD) technique, can significantly reduce the number of effective modes, allowing to handle complex spectral densities and enabling simulations at very low temperatures, including near-zero temperature dynamics.Another key improvement in the computational efficiency is the use of tensor network methods like matrix product states and hierarchical tensor networks. These techniques allow for efficient HEOM propagation with thousands of effective modes, crucial for simulating large molecular systems interacting with multiple baths. This combination enables simulations of excitation energy transfer (EET) in systems like the Fenna-Matthews-Olson (FMO) complex and even larger systems with experimentally determined spectral densities.The versatility of the HEOM method is demonstrated through applications to a wide range of chemical dynamics problems. Simulations of EET and related ultrafast spectroscopy are first briefly covered. Applications of the HEOM to quantum tunneling effects in proton transfer reactions are then presented. Early works have studied the non-Kramers dependence of the rate constant as a function of bath friction due to deep tunneling and revealed vibrationally nonadiabatic dynamics within the so-called nontraditional view of proton transfer reactions. A recent work on the large kinetic isotope effects in soybean lipoxygenase also indicated that many quantum correction approximations to classical transition-state theory may fall short in describing deep tunneling effects.Charge transport and separation dynamics in organic semiconductors are another area where the HEOM method has been instrumental. We first demonstrate that the HEOM provides a unified description of both band-like and thermally assisted charge carrier transport in organic materials. The effect of non-nearest neighbor transitions is then investigated by combining generalized master equations with exact memory kernels. The HEOM method also enables simulation of charge separation in organic photovoltaics (OPVs) and reveals how factors such as external electric fields, entropy, and charge delocalization influence the charge separation barrier and dynamics.Moreover, HEOM has been applied to investigate hydrogen atom scattering on the Au(111) surface and vibrational energy relaxation at molecule-metal interfaces. These studies provide deeper insights into how electron-hole pair excitations and temporary charge transfer states influence the nuclear motion, offering a new framework for simulating nonadiabatic dynamics on metal surfaces.In summary, the HEOM method has developed into a robust tool for simulating quantum effects in condensed phases. Future developments in algorithm efficiency and computational power will likely expand its applicability to even more complex systems.

Constrained nuclear-electronic orbital QM/MM approach for simulating complex systems with quantum nuclear delocalization effects incorporated

The hybrid quantum mechanics/molecular mechanics (QM/MM) approach, which combines the accuracy of QM methods with the efficiency of MM methods, is widely used in the study of complex systems. However, past QM/MM implementations often neglect or face challenges in addressing nuclear quantum effects, despite their crucial role in many key chemical and biological processes. Recently, our group developed the constrained nuclear-electronic orbital (CNEO) theory, a cost-efficient approach that accurately addresses nuclear quantum effects, especially quantum nuclear delocalization effects. In this work, we integrate CNEO with the QM/MM approach through the electrostatic embedding scheme and apply the resulting CNEO QM/MM to two hydrogen-bonded complexes. We find that both solvation effects and nuclear quantum effects significantly impact hydrogen bond structures and dynamics. Notably, in the glutamic acid–glutamate complex, which mimics a common low barrier hydrogen bond in biological systems, CNEO QM/MM accurately predicts nearly equal proton sharing between the two residues. With an accurate description of both quantum nuclear delocalization effects and environmental effects, CNEO QM/MM is a promising new approach for simulating complex chemical and biological systems.

Charge Transport in Interband Cascade Lasers: An Ab‐Initio Self‐Consistent Model

AbstractInterband cascade lasers (ICLs) stand out due to their low threshold current and minimal power consumption, rendering them viable sources for compact and mobile devices in the mid‐infrared. Since their first demonstration, they experienced major performance improvements. Mostly they originate from either improved material quality or the outcomes of numerical analysis of secluded parts. Encouraged by the impact of secluded models, an ICL‐specific simulation tool can lead to performance breakthroughs and a better comprehension of governing mechanisms. Drawing from an evaluation of existing tools designed for quantum cascade structures, a self‐consistent density matrix rate equation model is implemented to simulate the transport in both conduction and valence band heterostructures. Albeit the extensive inclusion of the quantum effects, special care was taken to maintain a high numerical efficiency. The charge transport model additionally considers optical field calculations, allowing for predictive calculations of light–current–voltage curves. The model is benchmarked against well‐established ICL designs and demonstrate reliable performance predictability. Additionally, detailed insights into device characteristics extracted from the model are provided. This ultimately allows to deepen the understanding of ICL and not only refine existing ones but also generate novel optimized designs.

Self-diffusion of liquid deuterium hydride and liquid tritium.

We present a quasi-elastic neutron scattering study of liquid deuterium hydride carried out using the Disk Chopper Spectrometer at the National Institute of Standards and Technology. Under saturated vapor pressure, the self-diffusion constant of deuterium hydride obeys an Arrhenius law D=D0exp-EA/kBT, where the prefactor D0 is given by D0=9.5±1.2Å2/ps and the activation energy is given by EA = 58 ± 2K. We apply the quantum law of corresponding states to the known diffusion constants of the hydrogen isotopologues. From this application, we estimate that D0≈9.1Å2/ps and EA ≈ 75K in liquid tritium. Young's theory of quantum-mechanical effects in van der Waals fluids [Young, Phys. Rev. A 23, 1498 (1981)] is shown to apply to the diffusion constants of the liquid hydrogens. Our results underscore the importance of nuclear quantum effects in shaping the properties and behavior of the hydrogen isotopologues.

Where is the hidden intramolecular H-bonding vibrational signal in the proline matrix IR spectrum?

The assignment of the hydrogen bonded O-H stretch vibration in the proline matrix IR spectrum has sparked controversy. Employing constrained nuclear electronic orbital methods, we provide a clear assignment that the vibrational frequency drops to near 3000cm-1 as a result of the interplay between electronic effects, nuclear quantum effects, and matrix effects.

Evidence of genuine quantum effects in nonequilibrium entropy production via quantum photonics

Evidence of genuine quantum effects in nonequilibrium entropy production via quantum photonics

Manipulating one-way quantum steering in a mechanical gain-loss optomechanical system

Based on the phenomenon of exceptional points (EPs) in the optomechanically induced mechanical PT-symmetric binary and ternary systems, we propose a mechanism to generate the perfect one-way quantum steering between two totally symmetric modes, respectively. By investigating the quantum steering behavior in the close vicinity of EP, we find that the optimal one-way quantum steering can be successfully generated at the EP in the PT-symmetric binary mechanical system. When pushing the system towards the EP, we show that not only is the broadest region of the one-way quantum steering achieved, but the robustness against the thermal noise can be significantly enhanced. In addition, the direction of the one-way quantum steering can be precisely controlled only by altering the sign of the detuning of the cavity field. What’s more, we analyze the mean populations of the involved modes to further support our findings and find that the occurrence of the one-way quantum steering depends mainly on the difference in the populations between the two target modes. We also successfully extend our findings to the high-order EP, and the desired one-way quantum steering can still be generated in the PT-symmetric ternary mechanical system when it operates at the EP. Our scheme opens up an alternative manipulation method to explore the various novel quantum effects exploiting the EPs and has significant potential applications in quantum nonreciprocal devices.

Light rings and shadows of static black holes in effective quantum gravity

Recently, two types of static black hole models that retain general covariance have been proposed within the Hamiltonian constraint approach to effective quantum gravity (EQG). We have studied the light rings and shadows of these black holes using the topological method and the backward ray-tracing method, respectively. We demonstrate that these light rings in both types of static black holes are standard and unstable according to the classification of light rings. Subsequently, we checked the position of the light rings using the photon trajectory equation. We found that although the quantum parameters do not affect the light rings of these two types of black holes, they do reduce the size of the first type of static black hole in EQG, making it smaller. However, for the second type of static black hole in EQG, we cannot distinguish it from a Schwarzschild black hole based on the shadow alone. Fortunately, the quantum parameters shrink the lensing rings of both types of black holes in EQG, causing the black hole shadow to occupy a larger proportion within the ring. This can serve as a basis for distinguishing whether the black hole is in EQG or general relativity (GR).

Quantum Effects at a Spin-Flop Transition in the Antiferromagnetic Topological Insulator MnBi2Te4

It is shown that the experimentally detected features in the low-temperature behavior of the magnetization in an external magnetic field perpendicular to the layers of manganese ions of the topological antiferromagnet MnBi2Te4 are due to quantum effects induced by the off-diagonal nature of the trigonal component of the crystal field. In this case, the anomalous increase in the magnetization of the material before the spin-flop transition, as well as after it in the phase of “collapsed” sublattices, is explained by the suppression of contributions from quantum effects. The comparison of the results of the theoretical analysis with experimental data has made it possible to refine the parameters of the effective spin model of MnBi2Te4 and to establish the important role of the noted trigonal component.

Quasi-normal modes of loop quantum black holes formed from gravitational collapse

In this paper, we study the quasi-normal modes (QNMs) of a scalar field in the background of a large class of quantum black holes that can be formed from gravitational collapse of a dust fluid in the framework of effective loop quantum gravity. The loop quantum black holes (LQBHs) are characterized by three free parameters, one of which is the mass parameter, while the other two are purely due to quantum geometric effects. Among these two quantum parameters, one is completely fixed by black hole thermodynamics and its effects are negligible for macroscopic black holes, while the second parameter is completely free (in principle). In the studies of the QNMs of such LQBHs, we pay particular attention to the difference of the QNMs between LQBHs and classical ones, so that they can be observed for the current and forthcoming gravitational wave observations, whereby place the LQBH theory directly under the test of observations.

Accurate nuclear quantum statistics on machine-learned classical effective potentials.

The contribution of nuclear quantum effects (NQEs) to the properties of various hydrogen-bound systems, including biomolecules, is increasingly recognized. Despite the development of many acceleration techniques, the computational overhead of incorporating NQEs in complex systems is sizable, particularly at low temperatures. In this work, we leverage deep learning and multiscale coarse-graining techniques to mitigate the computational burden of path integral molecular dynamics (PIMD). In particular, we employ a machine-learned potential to accurately represent corrections to classical potentials, thereby significantly reducing the computational cost of simulating NQEs. We validate our approach using four distinct systems: Morse potential, Zundel cation, single water molecule, and bulk water. Our framework allows us to accurately compute position-dependent static properties, as demonstrated by the excellent agreement obtained between the machine-learned potential and computationally intensive PIMD calculations, even in the presence of strong NQEs. This approach opens the way to the development of transferable machine-learned potentials capable of accurately reproducing NQEs in a wide range of molecular systems.

Scalar Quasi-Normal Modes of a loop quantum black hole

We compute the Quasi-Normal Mode (QNM) frequencies for scalar perturbations for modified Schwarzschild black holes in Loop Quantum Gravity. We study the singularity-free polymerized metric characterized by two parameters encoding loop quantum effects: the minimal area gap a 0 and the polymeric deformation parameter P. We perform numerical computations using Leaver's continued fraction method and compare our results to other semi-analytical methods and existing literature. We study the effects on the QNM spectrum of variation of both deformation parameters and systematically compare to the standard Schwarzschild case. In particular we find that the scalar fundamental mode is modified from the third decimal for values of P in accordance with the most recent astrophysical constraints. We also show that qualitative differences arise for highly damped modes: on the one hand, a new crossing of the imaginary axis occurs for high values of a 0 and, on the other hand, increasing P produces a positive shift of the real part and an increase of the spacing in imaginary part between modes.