Latest Papers in Condensed Matter Physics

Statistical Mechanics

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Spectral signatures of non-thermal baths in quantum thermalization (1903.07287v2)

Ricardo Román-Ancheyta, Barış Çakmak, Özgür E. Müstecaplıoğlu

2019-03-18

We show that certain coherences, termed as heat-exchange coherences, which contribute to the thermalization process of a quantum probe in a repeated interactions scheme, can be extracted from the power spectrum of the probe system. We suggest to use the power spectrum as a way to assess the apparent temperature of non-thermal atomic clusters carrying such coherences and also prove that it is useful to measure the corresponding thermalization time of the probe. We explore this idea in two examples in which the probe is assumed to be a single-qubit and a single-cavity field mode. Moreover, for the single-qubit case, we show how it is possible to perform a robust quantum simulation of resonance fluorescence using such repeated interactions scheme with clusters carrying different class of coherences.

Changeover in the transition nature of local-interaction Potts models: a new perspective (1808.04130v2)

Nir Schreiber, Reuven Cohen, Simi Haber, Gideon Amir, Baruch Barzel

2018-08-13

We present a novel combinatorial approach which allows the determination of the critical temperature and the phase transition order of Potts models with a round-the-face interaction. Using this approach, it is demonstrated that for some two dimensional ferromagnetic Potts models with completely local interaction there is a changeover in the transition order at a critical integer , where a first order transition is observed for and a second order transition is assumed at least for . This stands in contrast to the standard two-spin interaction Potts model where the critical integer value for which the transition is continuous is .

Thermometry in the quantum regime: Recent theoretical progress (1811.03988v2)

Mohammad Mehboudi, Anna Sanpera, Luis A. Correa

2018-11-09

Controlling and measuring the temperature in different devices and platforms that operate in the quantum regime is, without any doubt, essential for any potential application. In this review, we report the most recent theoretical developments dealing with accurate estimation of very low temperatures in quantum systems. Together with the emerging experimental techniques and developments of measurement protocols, the theory of quantum thermometry will decisively impinge and shape the forthcoming quantum technologies. While current quantum thermometric methods differ greatly depending on the experimental platform, the achievable precision, and the temperature range of interest, the theory of quantum thermometry is built under a unifying framework at the crossroads of quantum metrology, open quantum systems, and quantum many-body physics. At a fundamental level, theoretical quantum thermometry is concerned with finding the ultimate bounds and scaling laws that limit the precision of temperature estimation for systems in and out-of-thermal equilibrium. At a more practical level, it provides tools to formulate precise, yet feasible, thermometric protocols for relevant experimental architectures. Last but not least, the theory of quantum thermometry examines genuine quantum features, like entanglement and coherence, for their exploitation in enhanced-resolution thermometry.

Emergent interactions in conditioned processes: a route to smart matter? (1907.01383v1)

Francesco Cagnetta, Emil Mallmin

2019-07-02

We propose a method to derive `smart' active-matter interactions, such as collision avoidance, from first principles. Begin from a system with naive interactions, for example hardcore exclusion, and identify the natural fluctuations which by serendipity yield a high value of some relevant constituent performance, like mobility: in the effective dynamics describing these fluctuations smart interactions emerge. As a proof of concept, we examine two one-dimensional models of active matter: the totally asymmetric exclusion process and run-and-tumble particles. We show that the energy efficiency of motion, limited by particle collisions, can be increased up to a point of diminishing returns by conditioning on high mobility. Particular to the second model is the emergence of alignment interactions that allow substantial gains in efficiency, by preventing jamming without increasing energy consumption. We close by presenting features of our approach that go beyond the two models considered.

The Tangent Space to the Manifold of Critical Classical Hamiltonians Representable by Tensor Networks (1903.12137v3)

Yantao Wu

2019-03-28

We introduce a scheme to perform Monte Carlo Renormalization Group with the coupling constants of the system Hamiltonian encoded in a tensor network. With this scheme we compute the tangent space to the critical manifold at the nearest-neighbor critical coupling for three models: the two and three dimensional Ising models and the two dimensional three-state Potts model.

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