Electronically highly excited (Rydberg) atoms experience quantum state-changing interactions similar to Förster processes found in complex molecules, offering a model system to study the nature of dipole-mediated energy transport under the influence of a controlled environment. We demonstrate a nondestructive imaging method to monitor the migration of electronic excitations with high time and spatial resolution, using electromagnetically induced transparency on a background gas acting as an amplifier. The continuous spatial projection of the electronic quantum state under observation determines the many-body dynamics of the energy transport.

Rationale ER stress causes accumulation of misfolded proteins in the ER, activating the transcription factor, ATF6, which induces ER stress response genes. Myocardial ischemia induces the ER stress response; however, neither the function of this response nor whether it is mediated by ATF6 is known. Objective Here, we examined the effects of blocking the ATF6-mediated ER stress response on ischemia/reperfusion (I/R) in cardiac myocytes and mouse hearts. Methods and Results Knockdown of ATF6 in cardiac myocytes subjected to I/R increased ROS and necrotic cell death, which were mitigated by ATF6 overexpression. Under non-stressed conditions, WT and ATF6 knockout (KO) mouse hearts were similar. However, compared to WT, ATF6 KO hearts showed increased damage and decreased function upon I/R. Mechanistically, gene array analysis showed that ATF6, which is known to induce genes encoding ER proteins that augment ER protein-folding, induced numerous oxidative stress response genes not previously known to be ATF6-inducible. Many of the proteins encoded by the ATF6-induced oxidative stress genes identified here reside outside the ER, including catalase, which is known to decrease damaging ROS in the heart. Catalase was induced by the canonical ER stressor, tunicamycin, and by I/R in cardiac myocytes from WT but not in cardiac myocytes from ATF6 KO mice. ER stress response elements were identified in the catalase gene and were shown to bind ATF6 in cardiac myocytes, which increased catalase promoter activity. Overexpression of catalase, in vivo, restored ATF6 KO mouse heart function to WT levels in a mouse model of I/R, as did AAV9-mediated ATF6 overexpression. Conclusions ATF6 serves as a previously unappreciated link between the ER stress and oxidative stress gene programs, supporting a novel mechanism by which ATF6 decreases myocardial I/R damage.

We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional atomic gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Estimating rates for different excitation processes we conclude that the aggregates grow sequentially around an initial grain. Direct comparison with numerical simulations confirms this conclusion and reveals the presence of liquidlike spatial correlations. Our findings demonstrate the importance of dephasing in strongly correlated Rydberg gases and introduce a way to study spatial correlations in interacting many-body quantum systems without imaging.

We present the experimental observation of the antiblockade in an ultracold Rydberg gas recently proposed by Ates et al. [Phys. Rev. Lett. 98, 023002 (2007)]. Our approach allows the control of the pair distribution in the gas and is based on a strong coupling of one transition in an atomic three-level system, while introducing specific detunings of the other transition. When the coupling energy matches the interaction energy of the Rydberg long-range interactions, the otherwise blocked excitation of close pairs becomes possible. A time-resolved spectroscopic measurement of the Penning ionization signal is used to identify slight variations in the Rydberg pair distribution of a random arrangement of atoms. A model based on a pair interaction Hamiltonian is presented which well reproduces our experimental observations and allows one to deduce the distribution of nearest-neighbor distances.

We observe individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states coupled via an electromagnetically induced transparency resonance. Strong long-range interactions between Rydberg excitations give rise to a blockade between polaritons, resulting in large optical nonlinearities and modified polariton number statistics. By combining optical imaging and high-fidelity detection of the Rydberg polaritons we investigate both aspects of this coupled atom-light system. We map out the full nonlinear optical response as a function of atomic density and follow the temporal evolution of polaritons through the atomic cloud. In the blockade regime the statistical fluctuations of the polariton number drop well below the quantum noise limit. The low level of fluctuations indicates that photon correlations modified by the strong interactions have a significant back-action on the Rydberg atom statistics.Interfacing light and matter at the quantum level is at the heart of modern atomic and optical physics and enables new quantum technologies involving the manipulation of single photons and atoms. A prototypical atom-light interface is electromagnetically induced transparency (EIT) [1], which gives rise to hybrid states of photons and atoms called dark-state polaritons (DSPs) [2]. These long-lived quasi-particles simultaneously possess the properties of both the photonic and the atomic degrees of freedom, which can be interchanged in a fully coherent and reversible process. This has been intensively studied over the last decade, for instance, in the context of slow light [3], or to imprint a magnetic moment onto light fields [4] and to realize giant electrooptical effects [5]. Qualitatively new effects occur in strongly-interacting atomic systems in which the atomic admixture can mediate polariton-polariton interactions, leading to highly nonlinear [6][7][8] and nonlocal optical effects [9] as well as the emergence of correlations in both the atomic and the light fields [10,11]. The ability to produce and coherently control the propagation of quantum fields using interacting dark-state polaritons is expected to open up new applications including few photon nonlinear optics [6,11,12], non-classical light sources [7,10,[13][14][15][16], photonic quantum logic gates [16][17][18], and new types of strongly-interacting quantum gases [19].

We investigate Coherent Population Trapping in a strongly interacting ultracold Rydberg gas. Despite the strong van der Waals interactions and interparticle correlations, we observe the persistence of a resonance with subnatural linewidth at the single-particle resonance frequency as we tune the interaction strength. This narrow resonance cannot be understood within a meanfield description of the strong Rydberg-Rydberg interactions. Instead, a many-body density matrix approach, accounting for the dynamics of interparticle correlations, is shown to reproduce the observed spectral features.PACS numbers: 42.50. Gy,42.50.Ct,32.80.Ee Coherent population trapping (CPT), i.e. the population of a quantum state decoupled from a resonant light field, serves as a paradigm for a quantum interference effect [1]. First observed in 1976 [2], CPT with its related phenomena electromagnetically induced transparency (EIT) [3,4] and stimulated Raman adiabatic passage (STIRAP) [5] has provided the basis for a large variety of effects and applications in many areas of physics, such as high-resolution spectroscopy, coherent control, metrology, quantum information and quantum gases. While CPT, EIT and STIRAP are generally described in terms of isolated single-atom interactions with coherent light fields, the situation becomes more involved when interactions between the particles need to be considered.To gain initial insights into the effects of interactions on the quantum interference in CPT, consider two atoms with a three-level ladder structure with states |1 , |2 and |3 as shown in Fig. 1(a). The atoms are exposed to two resonant coherent light fields and interact only if both of them are in the highly excited atomic state |3 . In the case of non-interacting atoms the population accumulates in the two-body product state of the single-particle dark state |d which is a coherent superposition of |1 and |3 [1]. This state is defined as the eigenstate of the total Hamiltonian with vanishing coupling to the coherent light field. When turning on the interparticle interaction this state is no longer a dark state as it is no longer an eigenstate of the total Hamiltonian. As pointed out in [6], the two interacting atoms, nevertheless, possess two dark states |d ± . These states are dissipative due to the admixture of the intermediate, decaying state |2 , but are significantly populated by optical pumping. While these states have dissipative character, they do not contain the state |33 and are, thus, immune to interactions.In a first approach to a many-particle system one could apply a meanfield model by replacing many-body opera- PSfrag replacementsFIG. 1: (a) Excitation scheme ( 87 Rb). Ω1 and Ω2 are the Rabi frequencies at 780 and 480 nm, respectively, δ is the detuning of the upper transition; (b) calculated Rydberg state population, produced by the two-step sequence described in the text. The upper panel shows the result of a meanfield calculation, which predicts a strong shift and broadening of the resonance line. On the contrary, the...

Conceptually similar to modifications of DNA, mRNAs undergo chemical modifications, which can affect their activity, localization, and stability. The most prevalent internal modification in mRNA is the methylation of adenosine at the N6-position (m6A). This returns mRNA to a role as a central hub of information within the cell, serving as an information carrier, modifier, and attenuator for many biological processes. Still, the precise role of internal mRNA modifications such as m6A in human and murine-dilated cardiac tissue remains unknown. Transcriptome-wide mapping of m6A in mRNA allowed us to catalog m6A targets in human and murine hearts. Increased m6A methylation was found in human cardiomyopathy. Knockdown and overexpression of the m6A writer enzyme Mettl3 affected cell size and cellular remodeling both in vitro and in vivo. Our data suggest that mRNA methylation is highly dynamic in cardiomyocytes undergoing stress and that changes in the mRNA methylome regulate translational efficiency by affecting transcript stability. Once elucidated, manipulations of methylation of specific m6A sites could be a powerful approach to prevent worsening of cardiac function.

We propose a new all-optical method to image individual atoms within dense atomic gases. The scheme exploits interaction induced shifts on highly polarizable excited states, which can be spatially resolved via an electromagnetically induced transparency resonance. We focus in particular on imaging strongly interacting many-body states of Rydberg atoms embedded in an ultracold gas of ground state atoms. Using a realistic model we show that it is possible to image individual impurity atoms with enhanced sensitivity and high resolution despite photon shot noise and atomic density fluctuations. This new imaging scheme is ideally suited to equilibrium and dynamical studies of complex many-body phenomena involving strongly interacting atoms. As an example we study blockade effects and correlations in the distribution of Rydberg atoms optically excited from a dense gas.The ability to prepare and probe individual quantum systems in precisely controlled environments is a driving force in modern atomic, molecular and optical physics. More recently, new single atom and single site sensitive imaging techniques for optical lattices have opened the door to control and probe complex many-body quantum systems in strongly correlated regimes [7].The usual approach to detect atoms is to measure the fluorescence or absorption of light by driving a strong optical cycling-transition. Weak or open transitions present a difficulty since the maximum number of scattered photons per atom becomes greatly limited. In the case of long lived states of trapped ions, the technique of electron shelving has been used as an amplifying mechanism in order to directly observe quantum jumps [8]. Another approach involves the use of an optical cavity to enhance the interaction of the atoms with the light field [9]. This makes it possible to reach single-atom sensitivity, but usually at the expense of greatly reduced spatial resolution.Here we propose a new method to image individual atoms embedded within a dense atomic gas. The concept exploits strong interactions of the atoms with highly polarizable Rydberg states of the surrounding gas. The induced level shifts can then be transferred to a strong optical transition and to many surrounding atoms within a critical radius, thereby providing two mechanisms which greatly enhance the effect of a single impurity on the light field. The Rydberg states could act as non-destructive probes for individual trapped ions, nearby surface charges, dipolar molecules, or other Rydberg atoms. In our approach, the interaction-induced shifts are spatially resolved via an electromagneticallyinduced-transparency (EIT) resonance involving a weak