We present details of an experimental platform for studying Fermi polarons in a quantum-gas mixture. The system consists of about a thousand bosonic ^133Cs impurities immersed in a deeply degenerate Fermi gas (T/T_F ∼ 0.2) of approximately 2× 10^5 ^6Li atoms in a single hyperfine state, with interspecies interactions tunable via a Feshbach resonance. Using optical Raman spectroscopy without relative momentum transfer, we perform injection spectroscopy and thereby create the Fermi polaron. Owing to the large mass imbalance between the two species, the setup provides access to previously unexplored regimes of Fermi polarons.

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The Anderson orthogonality catastrophe (AOC) is a paradigmatic many-body phenomenon in which a local perturbation induces a macroscopic response of a Fermi sea. We probe signatures of the AOC by coherently driving heavy Fermi polarons in an ultracold ^6Li-^133Cs mixture. We observe a power-law dependence of the measured Rabi frequency on the drive strength, with exponents consistent with AOC predictions. Finite-temperature simulations quantitatively reproduce the observed scaling, indicating that AOC signatures persist beyond the idealized zero-temperature, infinite-mass limit. The damping of the Rabi oscillations provides access to polaron dephasing and reveals a nonmonotonic drive dependence, qualitatively consistent with current theories. Our results establish coherently driven impurities as a versatile probe of quantum many-body dynamics through local coherent control.

Magnetometry with nitrogen-vacancy (NV) centers in diamond has shown great promise in recent years. In particular, absorption-based magnetometry techniques, employing a cavity to enhance the absorption length, can improve the contrast and sensitivity compared to conventional techniques based on reading out the NV^- triplet fluorescence. The absorption techniques rely on magnetic-field-dependent absorption at the NV^- singlet zero phonon line at 1042nm and its phonon sideband. In a cavity-enhanced spectroscopy approach, we study pump-laser- and microwave-induced cavity signal changes at room temperature over a spectral range of 680-1050nm. Through normalization, we eliminate the cavity-enhancement effect and provide quasi-single-pass values for the absorption and optically detected magnetic resonance (ODMR) contrast. The highest contrast is found at 1042nm, but multiple points of high contrast are found at the peaks of the phonon sideband. Additionally, cavity-enhanced ODMR contrasts in the range of 50-80% are presented. We further measure the broadband singlet absorption cross section at room temperature with a novel method through microwave-induced signal changes. This method is insensitive to pump-laser-induced signal changes by other defects and quantifies the room-temperature absorption strength of the singlet transition and its entire phonon sideband. We determine the absorption cross section at 1042nm to be σ^ _1042=(0.89±0.14)· 10^-21 m^2 or σ^ ▴_1042=(2.9±0.5)· 10^-21 m^2. depending on the employed 532nm NV^- absorption cross section.

We report on the development of a modular platform for programmable quantum simulation with atomic quantum gases. The platform is centered around exchangeable optical modules with versatile functionalities. The performance of each module is disentangled from all others, enabling individual validation and maintenance of its outputs. The relative spatial positioning of the modules with respect to the position of the atomic sample is set by a global reference frame. In this way, the platform simplifies re-configuration and upgrading of existing setups and accelerates the design of new machines in a time- and cost-efficient manner. Furthermore, it facilitates collaboration among different experimental groups. This standardized hardware design framework, which we call Heidelberg Quantum Architecture, paves the way towards a new generation of on-demand and highly adaptable quantum simulation experiments.

Despite the fact that power-law interactions occur in a plethora of physical systems, their many-body dynamics is far less understood than that of nearest-neighbor interacting systems. Here, we study information scrambling in strongly disordered spin systems with power-law interactions via out-of-time-order correlators (OTOCs). Numerically, we find pronounced differences in the dynamical spreading of OTOCs between nearest-neighbor and power-law interacting systems. This deviation persists even for short-range interactions, opposing the common view that these interactions produce dynamics equivalent to the nearest-neighbor case. In a detailed experimental proposal, tailored but not limited to Rydberg tweezer setups, we present a protocol to extract OTOCs in XXZ Heisenberg spin systems with tunable anisotropy and programmable disorder based on currently available techniques.

We find energy-dependent hysteresis in an isolated Heisenberg quantum spin system, similar to thermomagnetic hysteresis in canonical spin glasses in contact with a thermal reservoir. Analogous to zero-field cooling and field cooling in conventional magnetic materials, an annealing protocol is devised to control the energy in an isolated system. Depending on the strength of disorder, the susceptibilities at zero field bifurcate at a specific energy, which signals the presence of different magnetic regimes. This behavior is apparent both in a numerical simulation by exact diagonalization of the Heisenberg Hamiltonian with twelve particles, as well as in an experiment with thousands of Rydberg atoms representing dipolar interacting quantum spins. The annealing protocols open a new path to explore the energy-dependent phase structure of spin systems at low energies. Our observation of a nonthermal metastable regime might indicate the existence of a phase transition to a novel state of isolated quantum spin systems.

We report on an imaging scheme for quantum gases that enables simultaneous detection of two spin states with single-atom resolution. It utilizes the polarization of the emitted photons during fluorescence by choosing appropriate internal states of lithium-6 atoms in a magnetic field. This scheme can readily be implemented to obtain in-situ spin correlations in a wide variety of experimental settings.

The amplitude and phase of a photoionization channel provide deep insights into the nature of ionization dynamics. Here, we propose a novel experimental approach to retrieve these parameters from the photoelectron momentum distribution (PMD), where a 400 nm femtosecond laser is used to ionize polarized Rb atoms prepared in the 5p state. The magnetic quantum numbers of polarized atoms are well controlled by breaking down the symmetry of the cooling laser in a magneto-optical trap reaction microscope. From the tilt angle of the PMD and the interference structure of εs and εd ionization channels, we are able to extract their relative amplitude and phase shift, in good agreement with ab initio calculations. This exhibits a benchmark one-photon single ionization study of the hydrogen-like atom, providing a complete measurement with full characterizations of intermediate and final state wave functions.

Time reversal in a macroscopic system contradicts daily experience. It is practically impossible to restore a shattered cup to its original state by just time reversing the microscopic dynamics that led to its breakage. Yet, with the precise control capabilities provided by modern quantum technology, the unitary evolution of a quantum system can be reversed in time. Here, we implement a time-reversal protocol in a dipolar interacting, isolated many-body spin system represented by Rydberg states in an atomic gas. By changing the states encoding the spin, we flip the sign of the interaction Hamiltonian, and demonstrate the reversal of the relaxation dynamics of the magnetization by letting a demagnetized many-body state evolve back in time into a magnetized state. We elucidate the role of atomic motion using the concept of a Loschmidt echo. Finally, by combining the approach with Floquet engineering, we demonstrate time reversal for a large family of spin models with different symmetries. Our method of state transfer is applicable across a wide range of quantum simulation platforms and has applications far beyond quantum many-body physics, reaching from quantum-enhanced sensing to quantum information scrambling.

An important step towards a comprehensive understanding of far-from-equilibrium dynamics of quantum many-body systems is the identification of unifying features that are independent of microscopic details of the system. We experimentally observe such robust features in the magnetization relaxation dynamics of disordered Heisenberg XX, XXZ, and Ising Hamiltonians. We realize these Heisenberg spin models with tunable anisotropy parameter and power-law interactions in an ensemble of Rydberg atoms by encoding the spin in suitable Rydberg state combinations. We consistently observe stretched-exponential relaxation of magnetization for all considered spin models, collapsing onto a single curve after appropriate rescaling of time. This robust short-time relaxation behavior is explained by a perturbative treatment that exploits the strong disorder in pairwise couplings, which leads to a description in terms of approximately independent pairs of spins. In numerical simulations of small systems, we show that these pairs of spins constitute approximate local integrals of motion, which remain at least partially conserved on a timescale exceeding the duration of the relaxation dynamics of the magnetization.

We developed a magneto-optical trap reaction microscope (MOTREMI) for strontium atoms by combining the multi-particle coincident detection with laser cooling technique. Present compact injection system can provide cold Sr atoms in three modes of 2D MOT, molasses and 3D MOT, delivering targets with adjustable densities and ratios of the ground state $5s^2$ ($^1S_{0}$) and the excited states $5s5p$ ($^{1}P_{1}$ and $^{3}P_{J}$ etc). The target profiles for the temperature, the density and the size of 3D MOT as well as cold atomic flux in 2D MOT model were characterized in details. With present state-of-the-art setup, we demonstrated the single photoionization of Sr atoms with molasses by absorption of few 800-nm photons, where Sr$^+$ and $e$ were detected in coincidence and most of ionization channels were identified taking into account photoelectron energy, laser-intensity dependence, and target dependence. The best momentum resolution of coincident Sr$^+$ and $e$ along time-of-flight are achieved up to 0.12 a.u. and 0.02 a.u., respectively. Present photoelectron momentum distributions ionized from the ground state and a few excited states illuminate unprecedentedly rich landscapes manifesting prominent features for multi-photon absorption. The full vector momenta of electrons and recoil ion in coincidence paves the way to further studying two-electron correlation dynamics and multi-electron effects in the multiple ionization of alkaline-earth atoms in the ultraviolet region.

The multichannel single photoionization of cold strontium atoms is investigated experimentally and theoretically with 800-nm femtosecond laser pulses of 35-fs duration at laser intensities of 3-6 TW/cm(2). The photoelectron energy spectra exhibit rich multipeak structures, which are identified as the multichannel ionization of the ground state 5s(2 1)S(0) and excited states 5s5p(1)P(1), 5s5p(3)P(2), and 5s4d(1)D(2). The photoelectron momentum distributions reveal distinct structures, and the corresponding photoelectron angular distributions provide valuable insights into the multiphoton ionization dynamics. As the laser intensity increases, the locations of the photoelectron energy peaks originating from the ionization of the excited states 5s5p(3)P(2) and 5s5p(1)D(2) remain unshifted, indicating the existence of Freeman resonance. The profiles from numerical solutions of the time-dependent Schrodinger equation (TDSE) are generally in agreement with the experimental results. However, some discrepancies, i.e., the ratio of partial waves contributing to the final states and tiny structures caused by resonance, may arise from the incomplete modeling of the valence-electron correlation effect in the present TDSE simulations based on the single-active-electron approximation.

We present the experimental apparatus enabling the observation of the heteronuclear Efimov effect in an optically trapped ultracold mixture of ^6 Li- ^133 Cs with high-resolution control of the interactions. A compact double-species Zeeman slower consisting of four interleaving helical coils allows for a fast-switching between two optimized configurations for either Li or Cs and provides an efficient sequential loading into their respective MOTs. By means of a bichromatic optical trapping scheme based on species-selective trapping we prepare mixtures down to 100 nK of 1× 10^4 Cs atoms and 7× 10^3 Li atoms. Highly stable magnetic fields allow high-resolution atom-loss spectroscopy and enable to resolve splitting in the loss feature of a few tens of milligauss. These features allowed for a detailed study of the Efimov effect.

Understanding how closed quantum systems dynamically approach thermal equilibrium presents a major unresolved problem in statistical physics. Generically, non-integrable quantum systems are expected to thermalize as they comply with the Eigenstate Thermalization Hypothesis. However, in the presence of strong disorder, the dynamics can possibly slow down to a degree that systems fail to thermalize on experimentally accessible timescales, as in spin glasses or many-body localized systems. In general, particularly in long-range interacting quantum systems, the specific nature of the disorder necessary for the emergence of a prethermal, metastable state–distinctly separating the timescales of initial relaxation and subsequent slow thermalization–remains an open question. We study an ensemble of Heisenberg spins with a tunable distribution of random coupling strengths realized by a Rydberg quantum simulator. We observe a drastic change in the late-time magnetization when increasing disorder strength. The data is well described by models based on pairs of strongly interacting spins, which are treated as thermal for weak disorder and isolated for strong disorder. Our results indicate a crossover into a pair-localized prethermal regime in a closed quantum system of thousands of spins in the critical case where the exponent of the power law interaction matches the spatial dimension.

The dynamics of correlated systems is relevant in many fields ranging from cosmology to plasma physics. However, they are challenging to predict and understand even for classical systems due to the typically large numbers of particles involved. Here, we study the evolution of an ultracold, correlated many-body system with repulsive interactions and initial correlations set by the Rydberg blockade using the analytical framework of Kinetic Field Theory (KFT). The KFT formalism is based on the path-integral formulation for classical mechanics and was first developed and successfully used in cosmology to describe structure formation in Dark Matter. The theoretical framework offers a high flexibility regarding the initial configuration and interactions between particles and, in addition, is computationally cheap. More importantly, the analytic approach allows us to gain better insight into the processes which dominate the dynamics. In this work we show that KFT can be applied in a much more general context and study the evolution of a correlated ion plasma. We find good agreement between the analytical KFT results for the evolution of the correlation function and results obtained from numerical simulations. We use the correlation functions obtained with KFT to compute the temperature increase in the ionic system due to disorder-induced heating. For certain choices of parameters we observe that the effect can be reversed, leading to correlation cooling. Due to its numerical efficiency as compared to numerical simulations, a detailed study using KFT can help to constrain parameter spaces where disorder-induced heating is minimal in order to reach the regime of strong coupling.

The study of cold and controlled molecular ions has been of key importance for a wide range of applications, such as the production of cold antihydrogen, creation and study of anionic Coulomb crystals and in atmospheric research and astrochemistry. However, the commonly used anion cooling technique via collisions with a buffer gas is limited by the temperature of the used cryogenic cooling medium. Here we demonstrate the forced evaporative cooling of anions via a laser beam with photon energies far above the photodetachment threshold of the anion. We cool an anionic ensemble from an initial temperature of 370(12) K down to 2.2(8) K. This results in a three orders of magnitude increase in the phase-space density of the ions, approaching the near-strong Coulomb coupling regime. We present an analysis of the cooling dynamics through a thermodynamic model that includes the role of intrinsic collisional heating, without any fitting parameters. This technique can be used to cool any anionic species below liquid helium temperature, providing a tool to push the frontiers of anion cooling below state-of-the-art temperature regimes. A common technique to cool down molecular ions is through collisions with a buffer gas, but that is limited by the achievable temperature of the medium. Now, an experiment demonstrates the evaporative cooling of molecular ions below previously reached temperatures.

Photoionization of the rubidium (Rb) atoms cooled in a magneto-optical trap, characterized by the coexistence of the ground 5$S_{1/2}$ and the excited 5$P_{3/2}$ states, is investigated experimentally and theoretically with the 400 nm femtosecond laser pulses at intensities of $I=3\times10^9$ W/cm$^2$ - $4.5\times10^{12}$ W/cm$^2$. Recoil-ion momentum distribution (RIMD) of Rb$^+$ exhibits rich ring-like structures and their energies correspond to one-photon ionization of the 5$P_{3/2}$ state, two-photon and three-photon ionizations of the 5$S_{1/2}$ state, respectively. With the increasing of $I$, we find that experimental signals near zero-momentum (NZM) in RIMDs resulted from the 5$P_{3/2}$ state enhance dramatically and its peaked Rb$^+$ momenta dwindle obviously while that from the 5$S_{1/2}$ state is maintained. Meanwhile, the ion-yield ratio of the 5$S_{1/2}$ over the 5$P_{3/2}$ states varies from $I$ to $I^{1.5}$ as $I$ increases. These features indicate a transition from perturbative ionization to strong-perturbative ionization for the 5$P_{3/2}$ state. Numerical simulations by solving the time-dependent Schr\"odinger equation (TDSE) can qualitatively explain the measurements of RIMD, photoion angular distributions, as well as ion-yield ratio. However, some discrepancies still exist, especially for the NZM dip, which could stem from the electron-electron correlation that is neglected in the present TDSE simulations since we have adopted the single-active-electron approximation.

Network science provides a universal framework for modeling complex systems, contrasting the reductionist approach generally adopted in physics. In a prototypical study, we utilize network models created from spectroscopic data of atoms to predict microscopic properties of the underlying physical system. For simple atoms such as helium, an a posteriori inspection of spectroscopic network communities reveals the emergence of quantum numbers and symmetries. For more complex atoms such as thorium, finer network hierarchies suggest additional microscopic symmetries or configurations. Furthermore, link prediction in spectroscopic networks yields a quantitative ranking of yet unknown atomic transitions, offering opportunities to discover new spectral lines in a well-controlled manner. Our work promotes a genuine bi-directional exchange of methodology between network science and physics, and presents new perspectives for the study of atomic spectra.

We theoretically investigate three-body losses in a single-component Fermi gas near a $p$-wave Feshbach resonance in the interacting, non-unitary regime. We extend the cascade model introduced by Waseem \textit{et al.} [M. Waseem, J. Yoshida, T. Saito, and T. Mukaiyama, Phys. Rev. A \textbf{99}, 052704 (2019)] to describe the elastic and inelastic collision processes. We find that the loss behavior exhibits a $n^3$ and an anomalous $n^2$ density dependence for a ratio of elastic-to-inelastic collision rate larger and smaller than 1, respectively. The corresponding evolutions of the energy distribution show collisional cooling or evolution toward low-energetic non-thermalized steady states, respectively. These findings are particularly relevant for understanding atom loss and energetic evolution of ultracold gases of fermionic lithium atoms in their ground state.