30 August 2018 Quantum Simulators with bosons

A dynamical lattice is simulated using a set of two-level atoms (orange) deeply confined in an optical lattice. Another lattice traps itinerant bosons (green) that interact among them and with the lat

An ICFO study published in Physical Review Letters proposes an in-depth study on boson interactions in quantum systems. Understanding and modelling the behaviour of quantum many-body systems tends to be a very complicated task, to such extent that it cannot be done efficiently with classical computers. Quantum simulators are ideal for these scenarios, since they are very versatile platforms that allow mimicking complex quantum systems in a controllable environment.

In such quantum systems, the interplay between electrons and phonons has been extensively studied, leading to the description of many important effects, including superconductivity, polaron formation and charge density waves. However, the same problem for bosons has not been extensively addressed.

The study of boson-lattice problems becomes very relevant in the context of quantum simulators. Ultra-cold atoms in optical lattices, in particular, allow one to experimentally address systems of strongly correlated bosons and to study their properties, which provides an interesting platform to study novel phenomena, such as super-solid phases or topological order.

In a paper recently published in Physical Review Letters, ICFO researchers Daniel González-Cuadra, Przemysław R. Grzybowski and Alexandre Dauphin led by ICREA Prof. at ICFO Maciej Lewenstein propose and analyze a one-dimensional model of interacting bosons coupled to a dynamical lattice. In particular, they report on the generation of an exotic quantum phase that can be realized with state-of-the-art experimental techniques using ultra-cold atoms in optical lattices: the bosonic Peierls insulator.

Using a model of interacting bosons coupled to a dynamical lattice represented by a set of two-level systems, the researchers showed that similar physics to the fermionic counterpart appear for sufficiently strong boson interactions. They showed, in particular, how the underlying lattice reorganize in different patterns depending on the bosonic density, giving rise to various bosonic Peierls insulators with different topological properties.

The proposed model provides, therefore, a unique playground to study the interplay between strong boson interactions, lattice dynamics, spontaneous symmetry breaking and topological effects in a cold atom setup.