Ultracold gases excited to strongly interacting Rydberg states are a promising system for quantum simulations of many-body systems. For off-resonant excitation of such systems in the dissipative regime, highly correlated many-body states exhibiting, among other characteristics, intermittency and multimodal counting distributions are expected to be created. Here we report on the realization of a dissipative gas of rubidium Rydberg atoms and on the measurement of its full counting statistics and phase diagram for both resonant and off-resonant excitation. We find strongly bimodal counting distributions in the off-resonant regime that are compatible with intermittency due to the coexistence of dynamical phases. Our results pave the way towards detailed studies of many-body effects in Rydberg gases.

The frequency shift of the center-of-mass oscillation, known as the (1,0) mode, of a trapped electron plasma and, furthermore, its time evolution were observed during the cooling of an injected antiproton beam for the first time. Here, antiprotons mixed with the electrons did not follow faster electron oscillations but contributed to the modification of the effective potential. The time evolution of the plasma temperature, deduced from the frequency shift of the excited (3,0) mode, suggested that there was an abnormal energy deposition of the antiproton beam in the electron plasma before thermalization.

We show that ultracold chemical reactions with an activation barrier can be tuned using Rydberg-dressed interactions. Scattering in the ultracold regime is sensitive to long-range interactions, especially when weakly bound (or quasibound) states exist near the collision threshold. We investigate how, by Rydberg dressing a reactant, one enhances its polarizability and modifies the long-range van der Waals collision complex, which can alter chemical reaction rates by shifting the position of near-threshold bound states. We carry out a full quantum mechanical scattering calculation for the benchmark system ${\mathrm{H}}_2+\mathrm{D}$, and show that resonances can be moved substantially and that rate coefficients at cold and ultracold temperatures can be increased by several orders of magnitude.

We study a broad class of epitaxial assembly of filament networks on lattice surfaces. Over time, a scale-free behavior emerges with a 2.5–3 power-law exponent in filament length distribution. Partitioning between the power-law and exponential behaviors in a network can be used to find the stage and kinetic parameters of the assembly process. To analyze real-world networks, we develop a computer program that measures the network architecture in experimental images. Application to triaxial networks of collagen fibrils shows quantitative agreement with our model. Our unifying approach can be used for characterizing and controlling the network formation that is observed across biological and nonbiological systems.

The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena of amorphous solids. Low temperature elastic measurements show that $e$-beam amorphous silicon ($a\text{−}\mathrm{Si}$) contains a variable density of TLSs which diminishes as the growth temperature reaches $400°\mathrm{C}$. Structural analyses show that these $a\text{−}\mathrm{Si}$ films become denser and more structurally ordered. We conclude that the enhanced surface energetics at a high growth temperature improved the amorphous structural network of $e$-beam $a\text{−}\mathrm{Si}$ and removed TLSs. This work obviates the role hydrogen was previously thought to play in removing TLSs in the hydrogenated form of $a\text{−}\mathrm{Si}$ and suggests it is possible to prepare “perfect” amorphous solids with “crystal-like” properties for applications.

Three-dimensional multicomponent plasmas composed of species with very different masses support a new branch of charge-density fluctuations known as acoustic plasmons. Here, we report on an ultrafast optical method to generate and probe coherent states of acoustic plasmons in a slab of GaAs, which relies on strong photoexcitation to create a large population of light electrons and heavy holes. Consistent with the random-phase-approximation theory, the data reveal standing plasma waves confined to these slabs, similar to those of conventional sound but with associated velocities that are significantly larger.

We demonstrate resonant coupling of a Mollow triplet sideband to an optical cavity in the strong coupling regime. We show that, in this regime, the resonant sideband is strongly enhanced relative to the detuned sideband. Furthermore, the linewidth of the Mollow sidebands exhibits a highly nonlinear pump power dependence when tuned across the cavity resonance due to strong resonant interactions with the cavity mode. We compare our results to calculations using the effective phonon master equation and show that the nonlinear linewidth behavior is caused by strong coherent interaction with the cavity mode that exists only when the Mollow sideband is near cavity resonance.

The ability to uniquely identify a quantum state is integral to quantum science, but for nonorthogonal states, quantum mechanics precludes deterministic, error-free discrimination. However, using the nondeterministic protocol of unambiguous state discrimination enables the error-free differentiation of states, at the cost of a lower frequency of success. We discriminate experimentally between nonorthogonal, high-dimensional states encoded in single photons; our results range from dimension $d=2$ to $d=14$. We quantify the performance of our method by comparing the total measured error rate to the theoretical rate predicted by minimum-error state discrimination. For the chosen states, we find a lower error rate by more than 1 standard deviation for dimensions up to $d=12$. This method will find immediate application in high-dimensional implementations of quantum information protocols, such as quantum cryptography.

We demonstrate the possibility to systematically steer the most probable escape paths (MPEPs) by adjusting relative noise intensities in dynamical systems that exhibit noise-induced escape from a metastable point via a saddle point. With the use of a geometric minimum action approach, an asymptotic theory is developed that is broadly applicable to fast-slow systems and shows the important role played by the nullcline associated with the fast variable in locating the MPEPs. A two-dimensional quadratic system is presented which permits analytical determination of both the MPEPs and associated action values. Analytical predictions agree with computed MPEPs, and both are numerically confirmed by constructing prehistory distributions directly from the underlying stochastic differential equation.

Many relevant applications in gravitational wave physics share a significant common problem: the seven-dimensional parameter space of gravitational waveforms from precessing compact binary inspirals and coalescences is large enough to prohibit covering the space of waveforms with sufficient density. We find that by using the reduced basis method together with a parametrization of waveforms based on their phase and precession, we can construct ultracompact yet high-accuracy representations of this large space. As a demonstration, we show that less than 100 judiciously chosen precessing inspiral waveforms are needed for 200 cycles, mass ratios from 1 to 10, and spin magnitudes $\le 0.9$. In fact, using only the first 10 reduced basis waveforms yields a maximum mismatch of 0.016 over the whole range of considered parameters. We test whether the parameters selected from the inspiral regime result in an accurate reduced basis when including merger and ringdown; we find that this is indeed the case in the context of a nonprecessing effective-one-body model. This evidence suggests that as few as $\sim 100$ numerical simulations of binary black hole coalescences may accurately represent the seven-dimensional parameter space of precession waveforms for the considered ranges.

We introduce a $N=1$ supergravity model with a very simple hidden sector coupled to the electroweak gauge and Higgs sectors of the minimal supersymmetric standard model. At the classical level, supersymmetry and $SU(2)\times U(1)$ are both spontaneously broken, with vanishing vacuum energy. Two real flat directions control the two symmetry-breaking scales $m_{3/2}$ and $m_Z$. The two massless scalars are a gauge singlet and the standard Higgs boson. All other unobserved particles have masses of order $m_{3/2}$. This may be a new starting point for studying the compatibility of naturalness with the observed mass hierarchies.

We compute leading-power fragmentation corrections to $J/\psi$ production at the Tevatron and the LHC. We find that, when these corrections are combined with perturbative corrections through next-to-leading order in the strong coupling constant ${\alpha }_s$, we obtain a good fit to high-$p_T$ cross section data from the CDF and CMS Collaborations. The fitted long-distance matrix elements lead to predictions of near-zero $J/\psi$ polarization in the helicity frame at large $p_T$.

We report the observation of macroscopic field-free orientation, i.e., more than 73% of CO molecules pointing in the same direction. This is achieved through an all-optical scheme operating at high particle densities ($>10^{17}{\mathrm{cm}}^{-3}$) that combines one-color ($\omega$) and two-color ($\omega +2\omega$) nonresonant femtosecond laser pulses. We show that the achieved orientation solely relies on the hyperpolarizability interaction as opposed to an ionization-depletion mechanism, thus, opening a wide range of applications. The achieved strong orientation enables us to reveal the molecular-frame anisotropies of the photorecombination amplitudes and phases caused by a shape resonance. The resonance appears as a local maximum in the even-harmonic emission around 28 eV. In contrast, the odd-harmonic emission is suppressed in this spectral region through the combined effects of an asymmetric photorecombination phase and a subcycle Stark effect, generic for polar molecules, that we experimentally identify.

A systematic investigation of the nuclear polarization effects in one- and few-electron heavy ions is presented. The nuclear polarization corrections in the zeroth and first orders in $1/Z$ are evaluated to the binding energies, the hyperfine splitting, and the bound-electron $g$ factor. It is shown that the nuclear polarization contributions can be substantially canceled simultaneously with the rigid nuclear corrections. This allows for new prospects for probing the QED effects in a strong electromagnetic field and the determination of fundamental constants.

We design a multimode interferometer with cold atoms confined in a harmonic trap. A first Kapitza-Dirac pulse creates several spatially addressable modes which are coherently recombined by the harmonic potential and mixed again by a second Kapitza-Dirac pulse. A phase shift among the mode is estimated by fitting the density profile or by measuring the number of atoms in each output mode. The expected sensitivity is rigorously calculated with the Fisher information and the Cramér-Rao lower bound. For the measurement of the gravitational acceleration $g$ we predict, with typical parameters of a compact setup, a temperature independent sensitivity which can exceed, by several orders of magnitude, the sensitivity of current atomic interferometers.

We study the optomechanical coupling of a oscillating effective mirror with a Rydberg atomic gas, mediated by the dynamical atom-mirror Casimir-Polder force. This coupling may produce a near-field resonant atomic excitation whose probability scales as $\propto (d^{2}a{n}^{4}t{)}^2/z_0^8$, where $z_0$ is the average atom-surface distance, $d$ the atomic dipole moment, $a$ the mirror’s effective oscillation amplitude, $n$ the initial principal quantum number, and $t$ the time. We propose an experimental configuration to realize this system with a cold atom gas trapped at a distance $\sim 2\times 10\mu \mathrm{m}$ from a semiconductor substrate whose dielectric constant is periodically driven by an external laser pulse, hence realizing an effective mechanical mirror motion due to the periodic change of the substrate from transparent to reflecting. For a parabolic gas shape, this effect is predicted to excite about $\sim 10^2$ atoms of a dilute gas of $10^3$ trapped Rydberg atoms with $n=75$ after about $0.5\mu \mathrm{s}$, which is high enough to be detected in typical Rydberg gas experimental conditions.

We investigated bistability with light beams in reorientational nematic liquid crystals. For a range of input powers, beams can propagate as either diffracting or self-trapped, the latter corresponding to spatial solitons. The first-order transition in samples exhibiting abrupt self-focusing with a threshold is in agreement with a simple model.

The turbulent energy flux through scales, $\overline{\epsilon }$, remains constant and nonvanishing in the limit of zero viscosity, which results in the fundamental anomaly of time irreversibility. It was considered straightforward to deduce from this the Lagrangian velocity anomaly, $⟨d{u}^2/dt⟩=-4\overline{\epsilon }$ at $t=0$, where $\overrightarrow{u}$ is the velocity difference of a pair of particles, initially separated by a fixed distance. Here we demonstrate that this assumed first taking the limit $t\to 0$ and then $\nu \to 0$, while a zero-friction anomaly requires taking viscosity to zero first. We find that the limits $t\to 0$ and $\nu \to 0$ do not commute if particles deplete (accumulate) in shocks backward (forward) in time on the viscous time scale. We compute analytically the resultant Lagrangian anomaly for one-dimensional Burgers turbulence and find it completely altered: $⟨d{u}^2/dt⟩$ has different values forward and backward in time. For incompressible flows, on the other hand, we show that the limits commute and the Lagrangian anomaly is still induced by the flux law, apparently due to a homogeneous distribution of fluid particles at all times.