Cold hybrid ion-atom systems

Using ultracold atomic systems as quantum simulators, many-body physics phenomena relevant to condensed matter systems can be explored. I will survey work in this area, and concentrate on the study of disorder in two-dimensional systems.

In this chapter, we will summarize some of the important results obtained in quantum simulation research into quantum many-body systems using ultracold atoms in an optical lattice. The extremely high controllability that is offered by systems of ultracold atoms in optical lattices has already allowed some highly impressive work to be accomplished. In particular, we focus on the two-electron atoms of ytterbium (Yb), which offer unique possibilities in the quantum simulation research field. After a brief introduction to the unique features of Yb atoms, we describe several important results, including the formation of strongly interacting Bose-Fermi mixtures and a novel SU(N) Mott insulator, a novel high-resolution laser spectroscopic method for measurement of the superfluid-Mott insulator transition, a quantum simulation of the impurity system with an Yb-Li (lithium) atomic mixture, the realization of nonstandard optical lattices, and the development of methods to manipulate interatomic interactions using both magnetic and optical Feshbach resonances.

We consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron-positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production including the backreaction leading to plasma oscillations. Unlike previous investigations on quantum link models, we focus on the infinite-dimensional Hilbert space of QED and show that it may be well approximated by experiments employing Bose-Einstein condensates interacting with fermionic atoms. The calculations based on functional integral techniques give a unique access to the physical parameters required to realize the QED phenomena in a cold atom experiment. In particular, we use our approach to consider quantum link models in a yet unexplored parameter regime and give bounds for their ability to capture essential features of the physics. The results suggest a paradigmatic change towards realizations using coherent many-body states rather than single atoms for quantum simulations of high-energy particle physics phenomena.

Interactions lie at the heart of correlated many-body quantum phases. Typically, the interactions between microscopic particles are described as two-body interactions. However, it has been shown that higher-order multi-body interactions could give rise to novel quantum phases with intriguing properties. So far, multi-body interactions have been observed as inelastic loss resonances in three- and four-body recombinations of atom-atom and atom-molecule collisions. Here we demonstrate the presence of effective multi-body interactions in a system of ultracold bosonic atoms in a three-dimensional optical lattice, emerging through virtual transitions of particles from the lowest energy band to higher energy bands. We observe such interactions up to the six-body case in time-resolved traces of quantum phase revivals, using an atom interferometric technique that allows us to precisely measure the absolute energies of atom number states at a lattice site. In addition, we show that the spectral content of these time traces can reveal the atom number statistics at a lattice site, similar to foundational experiments in cavity quantum electrodynamics that yield the statistics of a cavity photon field. Our precision measurement of multi-body interaction energies provides crucial input for the comparison of optical-lattice quantum simulators with many-body quantum theory.

Experimental progress in controlling and manipulating trapped atomic ions has opened the door for a series of proof-of-principle quantum simulations. This article reviews these experiments, together with the methods and tools that have enabled them, and provides an outlook on future directions in the field.

This topical review introduces the theoretical and experimental advances in continuous-variable (CV)—i.e. qumode-based in lieu of qubit-based—large-scale, fault-tolerant quantum computing and quantum simulation. An introduction to the physics and mathematics of multipartite entangled CV cluster states is given, and their connection to experimental concepts is delineated. Paths toward fault tolerance are also presented. It is the hope of the author that this review attract more contributors to the field and promote its extension to the promising technology of integrated quantum photonics.

We demonstrate novel implementations of high-precision optical magnetometers which allow for spatially-selective and spatially-resolved in situ measurements using cold atomic clouds. These are realised by using shaped dispersive probe beams combined with spatially-resolved balanced homodyne detection. Two magnetometer sequences are discussed: a vectorial magnetometer, which yields sensitivities two orders of magnitude better compared to a previous realisation and a Larmor magnetometer capable of measuring absolute magnetic fields. We characterise the dependence of single-shot precision on the size of the analysed region for the vectorial magnetometer and provide a lower bound for the measurement precision of magnetic field gradients for the Larmor magnetometer. Finally, we give an outlook on how dynamic trapping potentials combined with selective probing can be used to realise enhanced quantum simulations in quantum gas microscopes.

The rapid progress in quantum-optical experiments, especially in the field of cavity quantum electrodynamics and nanoplasmonics, allows one to substantially modify and control chemical and physical properties of atoms, molecules, and solids by strongly coupling to the quantized field. Alongside such experimental advances has been the recent development of ab initio approaches such as quantum electrodynamical density-functional theory (QEDFT), which is capable of describing these strongly coupled systems from first principles. To investigate response properties of relatively large systems coupled to a wide range of photon modes, ab initio methods that scale well with system size become relevant. In light of this, we extend the linear-response Sternheimer approach within the framework of QEDFT to efficiently compute excited-state properties of strongly coupled light–matter systems. Using this method, we capture features of strong light–matter coupling both in the dispersion and absorption properties of a molecular system strongly coupled to the modes of a cavity. We exemplify the efficiency of the Sternheimer approach by coupling the matter system to the continuum of an electromagnetic field. We observe changes in the spectral features of the coupled system as Lorentzian line shapes turn into Fano resonances when the molecule interacts strongly with the continuum of modes. This work provides an alternative approach for computing efficiently excited-state properties of large molecular systems interacting with the quantized electromagnetic field.

Arabic Named Entity Recognition (ANER) systems aim to identify and classify Arabic Named entities (NEs) within Arabic text. Other important tasks in Arabic Natural Language Processing (NLP) depends on ANER such as machine translation, question-answering, information extraction, etc. In general, ANER systems can be classified into three main approaches, namely, rule-based, machine-learning or hybrid systems. In this paper, we focus on research progress in machine-learning (ML) ANER and compare between linguistic resource, entity type, domain, method and performance. We also highlight the challenges when processing Arabic NEs through ML systems.

This review systematically examines the latest research progress and diverse applications of direct evaporative cooling and indirect evaporative cooling across five core sectors: industrial and energy engineering, the built environment, agriculture and food preservation, transportation and aerospace, and emerging interdisciplinary fields. While existing research often focuses on single application silos, this paper distills two common foundational challenges: climate adaptability and water resource management. Quantitative analysis demonstrates significant performance gains. Hybrid systems in data centers increase annual energy-saving potential by 14% to 41%, while precision root-zone cooling in greenhouses boosts crop yields by 13.22%. Additionally, passive cooling blankets reduce post-harvest losses by up to 45%, and integrated desalination cycles achieve 18.64% lower energy consumption compared to conventional systems. Innovative strategies to overcome humidity bottlenecks include vacuum-assisted membranes, advanced porous materials, and hybrid radiative-evaporative systems. The paper also analyzes sustainable water management through rainwater harvesting, seawater utilization, and atmospheric water capture. Collectively, these advancements provide a comprehensive framework to guide the future development and commercialization of sustainable cooling technologies.

Ramsey interferometry is an important technique in precision spectroscopy and quantum coherence measurement. The authors explore an innovative scheme in which splitter pulses are implemented by geometrical means, eliminating the temporal dependence of the atom-light interaction. This translates to an interferometer that is insensitive to the mean velocity of the atomic ensemble, making it suitable for applications in quantum computing and simulation, as well as atomtronic circuits. Using this geometric Ramsey interferometer, the team measures the phase accumulation during the free-evolution time due to a geometric scalar term.

Cognitive science is the interdisciplinary study of mind and intelligence, embracing psychology, neuroscience, linguistics, philosophy, anthropology, and computer modeling (artificial intelligence). After a review of the history of the field and its contributing disciplines, this chapter examines some of the main theoretical and experimental advances that cognitive science has accomplished over the past half-century, deriving lessons that might be useful for researchers in any emerging interdisciplinary area. The intellectual benefits of interdisciplinary research dramatically outweigh the personal and social difficulties of operating in more than one field. For theoretical, experimental, and practical progress, the separate disciplines that study the mind need to be interdependent, relying on each other for ideas and methods that complement their own.

Quantum simulation is one of the main contents of quantum information science, aiming to simulate and investigate poorly controllable or unobtainable quantum systems by using controllable quantum systems. Quantum simulation can be implemented in quantum computers, quantum simulators, and small quantum devices. Non-Hermitian systems have aroused research interest increasingly in recent two decades. On one hand, non-Hermitian quantum theories can be seen as the complex extensions of the conventional quantum mechanics, and are closely related to open systems and dissipative systems. On the other hand, both quantum systems and classical systems can be constructed as non-Hermitian systems with novel properties, which can be used to improve the precision of precise measurements. However, a non-Hermitian system is more difficult to simulate than a Hermitian system in that the time evolution of it is no longer unitary. In this review, we introduce recent research progress of quantum simulations of non-Hermitian systems. We mainly introduce theoretical researches to simulate typical non-Hermitian quantum systems by using the linear combinations of unitaries, briefly showing the advantages and limitations of each proposal, and we briefly mention other theoretical simulation methods, such as quantum random walk, space embedded and dilation. Moreover, we briefly introduce the experimental quantum simulations of non-Hermitian systems and novel phenomena in nuclear magnetic resonance, quantum optics and photonics, classical systems, etc. The recent progress of the combinations of quantum simulation and non-Hermitian physics has promoted the development of the non-Hermitian theories, experiments and applications, and expand the scope of application of quantum simulations and quantum computers.

Graph states are one of the most significant classes of entangled states, serving as the quantum resources for quantum technologies. Recently, integrated quantum photonics is becoming a promising platform for quantum information processing, enabling the generation, manipulation, and measurement of photonic quantum states. This article summarizes state-of-the-art experimental progress and advances in the chip-based photonic graph states.

Arrays of neutral-atom qubits in optical tweezers are a promising platform for quantum computation. Despite experimental progress, a major roadblock for realizing neutral-atom quantum computation is the qubit initialization. Here we propose that supersymmetry, a theoretical framework developed in particle physics, can be used for ultrahigh-fidelity initialization of neutral-atom qubits. We show that a single atom can be deterministically prepared in the vibrational ground state of an optical tweezer by adiabatically extracting all excited atoms to a supersymmetric auxiliary tweezer. The scheme works for both bosonic and fermionic atom qubits trapped in realistic Gaussian optical tweezers and may pave the way for realizing large-scale quantum computation, simulation, and information processing with neutral atoms.