Reproducing spin lattice models in strongly coupled atom-cavity systems

In an array of coupled cavities where the cavities are doped with an atomic V-system, and the two excited levels couple to cavity photons of different polarizations, we show how to construct various spin models employed in characterizing phenomena in condensed matter physics, such as the spin-1/2 Ising, XX, Heisenberg, and XXZ models. The ability to construct networks of arbitrary geometry also allows for the simulation of topological effects. By tuning the number of excitations present, the dimension of the spin to be simulated can be controlled, and mixtures of different spin types produced. The facility of single-site addressing, the use of only the natural hopping photon dynamics without external fields, and the recent experimental advances towards strong coupling, makes the prospect of using these arrays as efficient quantum simulators promising.Comment: 4 pages, 3 figures. v3: References adde

F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars

The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars. In the current study we show and discuss the evolution of broad-band radio spectra, which are measured at ten frequencies between 2.64 and 142 GHz using the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. It is argued that these can be attributed to only two classes of variability mechanisms. The first four types are dominated by spectral evolution and can be described by a simple two-component system composed of: (a) a steep quiescent spectral component from a large scale jet and (b) a time evolving flare component following the "Shock-in-Jet" evolutionary path. The fifth type is characterised by an achromatic change of the broad band spectrum, which could be attributed to a different mechanism, likely involving differential Doppler boosting caused by geometrical effects. Here we present the classification, the assumed physical scenario and the results of calculations that have been performed for the spectral evolution of flares.Comment: Proceedings of the conference: "The Central Kiloparsec in Galactic Nucleic: Astronomy at High Angular Resolution 2011", August 29 - September 2, 2011, Bad Honnef, German

Simulation of high-spin Heisenberg models in coupled cavities

We propose a scheme to realize the Heisenberg model of any spin in an arbitrary array of coupled cavities. Our scheme is based on a fixed number of atoms confined in each cavity and collectively applied constant laser fields, and is in a regime where both atomic and cavity excitations are suppressed. It is shown that as well as optically controlling the effective spin Hamiltonian, it is also possible to engineer the magnitude of the spin. Our scheme would open up an unprecedented way to simulate otherwise intractable high-spin problems in many-body physics.Comment: 4 pages, 2 figure

Photon blockade induced Mott transitions and XY spin models in coupled cavity arrays

As photons do not interact with each other, it is interesting to ask whether photonic systems can be modified to exhibit the phases characteristic of strongly coupled many-body systems. We demonstrate how a Mott insulator type of phase of excitations can arise in an array of coupled electromagnetic cavities, each of which is coupled resonantly to a {\em single} two level system (atom/quantum dot/Cooper pair) and can be individually addressed from outside. In the Mott phase each atom-cavity system has the same integral number of net polaritonic (atomic plus photonic) excitations with photon blockade providing the required repulsion between the excitations in each site. Detuning the atomic and photonic frequencies suppresses this effect and induces a transition to a photonic superfluid. We also show that for zero detuning, the system can simulate the dynamics of many body spin systems.Comment: 4 pages, 3 figure

Topological pumping of photons in nonlinear resonator arrays

We show how to implement topological or Thouless pumping of interacting photons in one dimensional nonlinear resonator arrays, by simply modulating the frequency of the resonators periodically in space and time. The interplay between interactions and the adiabatic modulations enables robust transport of Fock states with few photons per site. We analyze the transport mechanism via an effective analytic model and study its topological properties and its protection to noise. We conclude by a detailed study of an implementation with existing circuit QED architectures.Comment: 5 pages, 4 figures, and Supplemental Material. Comments are welcom

Floquet stroboscopic divisibility in non-Markovian dynamics

We provide a general discussion of the Liouvillian spectrum for a system coupled to a non-Markovian bath using Floquet theory. This approach is suitable when the system is described by a time-convolutionless master equation with time-periodic rates. Surprisingly, the periodic nature of rates allow us to have a stroboscopic divisible dynamical map at discrete times, which we refer to as Floquet stroboscopic divisibility. We illustrate the general theory for a Schr\"odinger cat which is roaming inside a non-Markovian bath, and demonstrate the appearance of stroboscopic revival of the cat at later time after its death. Our theory may have profound implications in entropy production in non-equilibrium systems.Comment: We changed the title and explained in more detail the definition of non-Markovian dynamics used in the manuscrip

Ammonia assimilation in Vitis vinifera L.: III. Glutamate oxaloacetate transaminase from leaf and root tissue

Glutamate-oxaloacetate transaminase (GOT) activities in Vitis vinifera L. cv. Chenin blanc leaf and root tissues were associated only with the soluble fraction. Mean in vitro enzyme activity of both tissues was 4.3 ± 0.8 μmol oxaloacetate formed per g fresh tissue per hour. Km values of GOT from leaves and roots were (1.9 ± 0.4) · 10-4 M for α-ketoglutarate and (4.7 ± 0.5) · 10-3 M for L-aspartate. Optimum in vitro conditions for GOT activity were pH 7.4-7.8, amount of enzyme equivalent to 95-130 mg fresh tissue and incubation temperature 38-39 °C. Neither leaf nor root GOT responded to exogenous pyridoxal-5' phosphate.Die Ammonium-Assimilation bei Vitis vinifera L.:III. GlutamatcOxalacetat-Transaminase aus Blatt- und WurzelgewebeDie Aktivität der Glutamat-Oxalacetat-Transaminase (GOT) in Blatt- und Wurzelgewebe der Rebsorte Chenin blanc (Vitis vinifera L.) war auf die lösliche Fraktion beschränkt. In vitro betrug die mittlere Enzymaktivität in beiden Organen 4,3 ± 0,8 μmol Oxalacetat je g Frischgewicht und h. Die Km-Werte von GOT aus Blättern und Wurzeln betrugen (1,9±0,4) . 10-4 M für α-Ketoglutarat und (4,7±0,5) · 10-3 M für L-Aspartat. Die optimalen Bedingungen der GOT-Aktivität waren in vitro ein pH von 7,4-7,8, eine Enzymmenge, die dem Gehalt von 95-130 mg Frischmaterial entsprach, und eine Inkubationstemperatur von 38-39 °C. Weder Blatt- noch Wurzel-GOT reagierten auf zugesetztes Pyridoxal-5'-Phosphat