DQMP Forum - Josephson junction array modeling of an out of equilibrium supersolid - Growth and preservation of entanglement in a many-body localized array of superonducting qubits

30.06.2020 13:00 – 14:00

Josephson junction array modeling of an out of equilibrium supersolid
Giacomo Morpurgo (group of Prof. Giamarchi)

The supersolid phase is an exotic state of matter which has elements of both solids and superfluids. It has at the same time a crystalline order and a superfluid order. People have tried to obtain this phase in condensed matter systems, for instance with bulk Helium-4 but with no evident success. However this phase was recently achieved with dipolar atoms (using atoms with a large magnetic moment) in ultracold gases. [1]
To better understand the dynamics of such a phase, we looked at a supersolid system viewed as a Josephson Junction array and studied the global phase coherence when quenching the Josephson interaction term in a quasi-classical regime with Langevin formalism. We looked at the loss of phase coherence when the interaction term becomes negligible and at the regain of phase coherence when the interaction term becomes again non-negligible. In this talk I will discuss these results and compare them with experimental results. [2]
[1] Long-Lived and Transient Supersolid Behaviors in Dipolar Quantum Gases, L.Chomaz et al, Phys. Rev. X 9, 021012
[2] Phase coherence in out-of-equilibrium supersolid states of ultracold dipolar atoms, P.Ilzhfer et al, arXiv :1912.10892


Growth and preservation of entanglement in a many-body localized array of superonducting qubits
Michele Filippone (group of prof. Giamarchi)

Disclaimer: an experimental talk made by a theorist! :)
Is it possible to harness and preserve the quantum coherent properties of many-body systems? This project seems doomed to fail, as interactions in many-body systems generally lead to ergodicity, namely the inevitable loss of quantum coherence and memory about initial conditions. Nevertheless, the recent discovery of many-body localization (MBL) – a generalization of Anderson localization in the presence of interactions – has shown the possibility to circumvent ergodicity. Nowadays, a key challenge is to measure interaction induced dynamics of particles and of entanglement between the localized sites in this phase. By studying interacting photons in an array of superconducting qubits, we observe ergodicity breaking and directly measure the effective non-local interactions. We probe the entanglement signatures of MBL in 1D and 2D and observe the slow growth of entanglement entropy. Our work elucidates the fundamental mechanisms of entanglement formation, propagation, and preservation in the MBL phase of matter. [1]
[1] https://arxiv.org/abs/1910.06024

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