Preliminary characterization of the stratospheric circulation using long-lived tracers with the WACCM chemistry-climate model and observations

The changes in stratospheric circulation are one of the major sources of uncertainty in climate projection, therefore they are a major area of research. The current work is part of the ACCROSS (Atmospheric Composition and Circulation investigated with meteorological Reanalyses, Observational datasets and models for the Study of the Stratosphere and its changes) project, which intends to improve our understanding of the circulation changes in the past years through an extensive use of observations and model simulations of selected long-lived tracers. Here we compare simulations of a state-of-the-art Chemistry Climate Model with satellite observations of HF and N2O from February 2004 to February 2013. To accomplish this task major modifications to the model chemistry scheme have been made. This early comparison shows poor agreement in the HF distribution in the middle stratosphere for all latitudes, while in the low stratosphere the agreement is better, especially in the tropics. Since good agreement is found in the N2O distribution, the residual circulation is well represented, e.g. the model reproduces well the position of the transport barriers in the SH, this suggests that the disagreement in the HF distributions is due to an incomplete chemical scheme. A comparison with chemistry-transport models using the same chemistry scheme and boundary conditions is needed to evaluate this point

Dynamical properties of dissipative XYZ Heisenberg lattices

We study dynamical properties of dissipative XYZ Heisenberg lattices where anisotropic spin-spin coupling competes with local incoherent spin flip processes. In particular, we explore a region of the parameter space where dissipative magnetic phase transitions for the steady state have been recently predicted by mean-field theories and exact numerical methods. We investigate the asymptotic decay rate towards the steady state both in 1D (up to the thermodynamical limit) and in finite-size 2D lattices, showing that critical dynamics does not occur in 1D, but it can emerge in 2D. We also analyze the behavior of individual homodyne quantum trajectories, which well reveal the nature of the transition

Homodyne versus photon-counting quantum trajectories for dissipative Kerr resonators with two-photon driving

We investigate two different kinds of quantum trajectories for a nonlinear photon resonator subject to two-photon pumping, a configuration recently studied for the generation of photonic Schroedinger cat states. In the absence of feedback control and in the strong-driving limit, the steady-state density matrix is a statistical mixture of two states with equal weight. While along a single photon-counting trajectory the systems intermittently switches between an odd and an even cat state, we show that upon homodyne detection the situation is different. Indeed, homodyne quantum trajectories reveal switches between coherent states of opposite phase.Comment: To appear on Eur. Phys. J. Special Topics, Quantum Gases and Quantum Coherence; 8 pages, 2 composed figures (5 panels

Mineral composition of organic and conventional white wines from Italy

Despite of the increased interest of consumers for organic agro-food products and of the growing demand for organic wines, scientific literature reports a limited number of studies aimed to evaluate the chemical composition of organic wine with respect to conventional wine in terms of major and trace metals. In the present study the concentrations of 19 elements (Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) were determined in samples of white wines from Italy, conventionally and organically produced. No significant difference in the mineral composition was found between the two groups, except for Ni, which showed a higher concentration in organic wines. By comparing our data with data from literature it can be pointed out that there is no agreement among the results presented in the different studies referring to comparisons between organically and conventionally produced wines, concluding that the mineral composition of wines depends on factors different from organic/conventional production method

A critical Schr\"odinger cat qubit

Encoding quantum information onto bosonic systems is a promising route to quantum error correction. In a cat code, this encoding relies on the confinement of the system's dynamics onto the two-dimensional manifold spanned by Schr\"odinger cats of opposite parity. In dissipative cat qubits, an engineered dissipation scheme combining two-photon drive and two-photon dissipation autonomously stabilize this manifold, ensuring passive protection against, e.g., phase-flip errors regardless of their origin. Similarly, in Kerr cat qubits, where highly-performing gates can be engineered, two-photon drive and Kerr nonlinearity cooperate to confine the system to the ground state manifold spanned by the cats. Dissipative, Hamiltonian, and hybrid confinement mechanisms have been mainly investigated at resonance. Here, we propose a critical cat code, where both two-photon dissipation and Kerr nonlinearity are present and the two-photon drive is allowed to be out of resonance. The competition between nonlinearity and detuning triggers a first-order dissipative phase transition, making the encoding efficient over a wide range of parameters. The performance of the code is benchmarked within the general framework of the Liouvillian spectral theory. We introduce a channel-fidelity decay rate, allowing a fair comparison between our critical stabilization mechanism and its Hamiltonian, dissipative, and resonant-hybrid counterparts in the presence of both photon loss and dephasing noise. The critical cat outperforms the others, and this enhanced performance lies within reach of current experimental setups. Efficiently operating over a broad range of detuning values, the critical cat code is particularly resistant to random frequency shifts characterizing multiple-qubit operations, opening venues for the realization of reliable protocols for scalable and concatenated bosonic qubit architectures.Comment: 21 pages, 15 figure