In this work we study the heat transport in an XXZ spin-1/2 Heisenberg chain with homogeneous magnetic field, incoherently driven out of equilibrium by reservoirs at the boundaries. We focus on the effect of bulk dephasing (energydissipative) processes in different parameter regimes of the system. The nonequilibrium steady state of the chain is obtained by simulating its evolution under the corresponding Lindblad master equation, using the time evolving block decimation method. In the absence of dephasing, the heat transport is ballistic for weak interactions, while being diffusive in the strongly-interacting regime, as evidenced by the heat-current scaling with the system size. When bulk dephasing takes place in the system, diffusive transport is induced in the weakly-interacting regime, with the heat current monotonically decreasing with the dephasing rate. In contrast, in the stronglyinteracting regime, the heat current can be significantly enhanced by dephasing for systems of small size.

We report the observation of vortex nucleation in a rotating optical lattice. A 87 Rb Bose-Einstein condensate was loaded into a static two-dimensional lattice and the rotation frequency of the lattice was then increased from zero. We studied how vortex nucleation depended on optical lattice depth and rotation frequency. For deep lattices above the chemical potential of the condensate we observed a linear dependence of the number of vortices created with the rotation frequency, even below the thermodynamic critical frequency required for vortex nucleation. At these lattice depths the system formed an array of Josephson-coupled condensates. The effective magnetic field produced by rotation introduced characteristic relative phases between neighbouring condensates, such that vortices were observed upon ramping down the lattice depth and recombining the condensates.PACS numbers: 03.75. Lm, 67.85.Hj, 74.50.+r, 74.81.Fa Ultracold quantum gases in rotating optical lattices find themselves at the intersection of two fields which have generated an impressive body of experimental and theoretical work. The versatile and clean potentials offered by optical lattices have proved to be an incredibly adept system for exploring a wide range of fundamental problems in condensed matter physics such as the Mott-insulator transition [1], Anderson localization [2,3] and Tonks-Girardeau gases [4]. Similarly rotating quantum gases have provided an array of striking results, from the nucleation of vortex lattices in Bose gases [5,6] to rotating Fermi gases at the BCS-BEC crossover [7]. The close analogy between the physics of rapidly rotating neutral atoms and electrons under a magnetic field has led to considerable interest in the possibility of achieving strongly-correlated quantum Hall states in a rapidly rotating atomic gas [8,9].Rotating optical lattices for cold atoms have generated a large amount of interest in their own right, which can broadly be divided into three main areas: (i) Weak rotating lattices have been used to pin vortices [10] and theoretical work has shown that rich vortex lattices structures, including lattices of doubly quantized vortices, are predicted to emerge [11,12]; (ii) Stronger optical lattice potentials with a large number of atoms per site (100-1000) realize the physics of Josephson junction arrays (JJA) under magnetic fields [13,14]; (iii) Arguably the most interesting regime is for a dilute gas in the tight binding regime in a rotating lattice where fractional quantum Hall physics is predicted to occur [15][16][17]. In all three regimes rich structures emerge that depend on the relative density of vortices and lattice sites.We report on the first experiments with a rotating optical lattice in the 'deep' lattice regime where lattices depths were reached such that a 2D array of weakly linked condensates was created, forming a Josephson junction array. Under rotation this system realizes the uniformly frustrated JJA [13,18]. We have investigated the nucleation of vortices in a rotating lattice, start...

Recent experiments performed on cuprates and alkali-doped fullerides have demonstrated that key signatures of superconductivity can be induced above the equilibrium critical temperature by optical modulation. These observations in disparate physical systems may indicate a general underlying mechanism. Multiple theories have been proposed, but these either consider specific features, such as competing instabilities, or focus on conventional BCS-type superconductivity. Here we show that periodic driving can enhance electron pairing in strongly correlated systems. Focusing on the strongly repulsive limit of the doped Hubbard model, we investigate in-gap, spatially inhomogeneous, on-site modulations. We demonstrate that such modulations substantially reduce electronic hopping, while simultaneously sustaining superexchange interactions and pair hopping via driving-induced virtual charge excitations. We calculate real-time dynamics for the one-dimensional case, starting from zero- and finite-temperature initial states, and we show that enhanced singlet-pair correlations emerge quickly and robustly in the out-of-equilibrium many-body state. Our results reveal a fundamental pairing mechanism that might underpin optically induced superconductivity in some strongly correlated quantum materials

Abstract. In this technical paper we introduce the Tensor Network Theory (TNT) library -an open-source software project aimed at providing a platform for rapidly developing robust, easy to use and highly optimised code for TNT calculations. The objectives of this paper are (i) to give an overview of the structure of TNT library, and (ii) to help scientists decide whether to use the TNT library in their research. We show how to employ the TNT routines by giving examples of ground-state and dynamical calculations of one-dimensional bosonic lattice systems. We also discuss different options for gaining access to the software available at http://www.tensornetworktheory.org.

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 the 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.

We demonstrate a novel experimental arrangement which can rotate a 2D optical lattice at frequencies up to several kilohertz. Ultracold atoms in such a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, allowing investigation of phenomena such as the fractional quantum Hall effect. Our arrangement also allows the periodicity of a 2D optical lattice to be varied dynamically, producing a 2D accordion lattice.

The exciton relaxation dynamics of photoexcited electronic states in poly(p-phenylenevinylene) are theoretically investigated within a coarse-grained model, in which both the exciton and nuclear degrees of freedom are treated quantum mechanically. The Frenkel-Holstein Hamiltonian is used to describe the strong exciton-phonon coupling present in the system, while external damping of the internal nuclear degrees of freedom is accounted for by a Lindblad master equation. Numerically, the dynamics are computed using the time evolving block decimation and quantum jump trajectory techniques. The values of the model parameters physically relevant to polymer systems naturally lead to a separation of time scales, with the ultra-fast dynamics corresponding to energy transfer from the exciton to the internal phonon modes (i.e., the C-C bond oscillations), while the longer time dynamics correspond to damping of these phonon modes by the external dissipation. Associated with these time scales, we investigate the following processes that are indicative of the system relaxing onto the emissive chromophores of the polymer: (1) Exciton-polaron formation occurs on an ultra-fast time scale, with the associated exciton-phonon correlations present within half a vibrational time period of the C-C bond oscillations. (2) Exciton decoherence is driven by the decay in the vibrational overlaps associated with exciton-polaron formation, occurring on the same time scale. (3) Exciton density localization is driven by the external dissipation, arising from "wavefunction collapse" occurring as a result of the system-environment interactions. Finally, we show how fluorescence anisotropy measurements can be used to investigate the exciton decoherence process during the relaxation dynamics.

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