arXiv subjects

Jean-Baptiste Bouhiron

Publications and source records attributed to Jean-Baptiste Bouhiron.

5 recordsLinked to original sources

arXiv2024

Realization of an atomic quantum Hall system in four dimensions

Modern condensed matter physics relies on the concept of topology to classify matter, from quantum Hall systems to topological insulators. Engineered systems, benefiting from synthetic dimensions, can potentially give access to novel topological states predicted in dimensions $D > 3$. We report the realization of an atomic quantum Hall system evolving in four dimensions (4D), with two spatial dimensions and two synthetic ones encoded in the large spin of dysprosium atoms. The non-trivial topology is evidenced by measuring a quantized electromagnetic non-linear response and observing anisotropic hyperedge modes. We also excite non-planar cyclotron motion, contrasting with its circular equivalents in $D\leq3$. Our work opens to the investigation of strongly-correlated topological liquids in 4D generalizing fractional quantum Hall states.

cond-mat.quant-gas↗

arXiv2023

Realizing the entanglement Hamiltonian of a topological quantum Hall system

Topological quantum many-body systems, such as Hall insulators, are characterized by a hidden order encoded in the entanglement between their constituents. Entanglement entropy, an experimentally accessible single number that globally quantifies entanglement, has been proposed as a first signature of topological order. Conversely, the full description of entanglement relies on the entanglement Hamiltonian, a more complex object originally introduced to formulate quantum entanglement in curved spacetime. As conjectured by Li and Haldane, the entanglement Hamiltonian of a many-body system appears to be directly linked to its boundary properties, making it particularly useful for characterizing topological systems. While the entanglement spectrum is commonly used to identify complex phases arising in numerical simulations, its measurement remains an outstanding challenge. Here, we perform a variational approach to realize experimentally, as a genuine Hamiltonian, the entanglement Hamiltonian of a synthetic quantum Hall system. We use a synthetic dimension, encoded in the electronic spin of dysprosium atoms, to implement spatially deformed Hall systems, as suggested by the Bisognano-Wichmann prediction. The spectrum of the optimal variational Hamiltonian exhibits a chiral dispersion akin to a topological edge mode, revealing the fundamental link between entanglement and boundary physics. Our variational procedure can be easily generalized to interacting many-body systems on various platforms, marking an important step towards the exploration of exotic quantum systems with long-range correlations, such as fractional Hall states, chiral spin liquids and critical systems.

cond-mat.quant-gas↗

arXiv2021

Laughlin's topological charge pump in an atomic Hall cylinder

The quantum Hall effect occuring in two-dimensional electron gases was first explained by Laughlin, who envisioned a thought experiment that laid the groundwork for our understanding of topological quantum matter. His proposal is based on a quantum Hall cylinder periodically driven by an axial magnetic field, resulting in the quantized motion of electrons. We realize this milestone experiment with an ultracold gas of dysprosium atoms, the cyclic dimension being encoded in the electronic spin and the axial field controlled by the phases of laser-induced spin-orbit couplings. Our experiment provides a straightforward manifestation of the non-trivial topology of quantum Hall insulators, and could be generalized to strongly-correlated topological systems.

cond-mat.quant-gas↗

arXiv2021

Simulating two-dimensional dynamics within a large-size atomic spin

Encoding a dimension in the internal degree of freedom of an atom provides an interesting tool for quantum simulation, facilitating the realization of artificial gauge fields. We propose an extension of the synthetic dimension toolbox, making it possible to encode two dimensions within a large atomic spin. The protocol combines first- and second-order spin couplings, such that the spin projection $m$ and the remainder $r=m$ (mod 3) of its Euclidian division by 3 act as orthogonal coordinates on a synthetic cylinder. It is suited for an implementation with lanthanide atoms, which feature a large electronic spin and narrow optical transitions for applying the required spin couplings. This method is useful for simulating geometries with periodic boundary conditions, and engineering various types of topological systems evolving in high dimensions.

cond-mat.quant-gas↗

arXiv2021

Partitioning dysprosium's electronic spin to reveal entanglement in non-classical states

Quantum spins of mesoscopic size are a well-studied playground for engineering non-classical states. If the spin represents the collective state of an ensemble of qubits, its non-classical behavior is linked to entanglement between the qubits. In this work, we report on an experimental study of entanglement in dysprosium's electronic spin. Its ground state, of angular momentum $J=8$, 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. Starting with the well-known W and squeezed states, we extract the concurrence of qubit pairs, which quantifies their 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 probe decoherence of a state prepared in the excited level $J'=J+1$ and interpret spontaneous emission as a loss of a qubit pair in a random state. This allows us to contrast the robustness of pairwise entanglement of the W state with the fragility of the coherence involved in a Schrödinger cat state. Our findings open up the possibility to engineer novel types of entangled atomic ensembles, in which entanglement occurs within each atom's electronic spin as well as between different atoms.

quant-ph↗