Group Seminar via Zoom: Entanglement in non-classical spin states and realisation of a Laughlin charge pump with ultracold dysprosium

Tanish Satoor, Laboratoire Kastler Brossel
Group Seminar via video conference (Zoom)
Tuesday, September 21st, 9:00 am (MEZ)

Due to the Covid-19 pandemic, we are now holding our group seminars and journal clubs via video conference.This procedure enables us to continue our research, enhance discussions and exchange important information.

Abstract:

In this talk, I will focus on two recent projects from our dysprosium quantum gas experiment. Firstly, we describe a study of entanglement within non-classical spin states of the electronic ground state spin J=8 of dysprosium [1]. This spin can formally be viewed as a set of 2J qubits symmetric upon exchange. To access entanglement properties, we partition the spin by optically coupling it to an excited state J'=J-1, which removes a pair of qubits in a state defined by the light polarization. For the well-known W and Schrödinger cat states, we measure the concurrence of the extracted qubit pair, which quantifies its non-classical character. We also directly demonstrate entanglement between the 14- and 2-qubit subsystems via an increase in entropy upon partition. In a complementary set of experiments, we prepare these states in the excited level J'=J+1 and interpret spontaneous emission as a loss of a qubit pair in a random state.

In contrast, the second part of the talk is based on exploiting the spin J=8 as a synthetic dimension to engineer artificial gauge fields. After a brief recap of our realisation of a Quantum hall system in a 2D ribbon geometry [2], we focus on our recent scheme to extend this to a cylindrical geometry, using laser couplings to engineer a periodic synthetic dimension. We characterize the lowest energy band properties, and probe its transverse linear response to reveal its underlying topological character. Finally, we realise Laughlin's charge pump by applying a magnetic flux along the cylinder axis and measuring an atomic displacement consistent with the band's topology.

[1]: T Satoor, A Fabre, JB Bouhiron, A Evrard, R Lopes & S Nascimbene, arXiv:2104.14389 (2021)

[2]: T Chalopin, T Satoor, A Evrard, V Makhalov, J Dalibard, R Lopes & S Nascimbene, Nature Physics 16, 1017–1021 (2020)

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