Alexander Poddubny Group

Research

In recent years, the quantum physics landscape has been reshaped by the emergence of diverse artificial quantum optical systems. In these systems, photons interact with multiple emitters—be it atoms, superconducting qubits, solid-state defects, or quantum dots. An intriguing aspect of these interactions is the reabsorption of emitted photons by remote emitters, initiating a photon-mediated coupling across significant distances. This long-range, collective coupling introduces unique properties to atom-photon systems.

We study theoretically various phenomena found within arrays of photon emitters, including both natural and artificial atoms, lasers, and particularly within topologically complex lattices. Our main setup is an array of emitters coupled to waveguide as in the video above. Our mission is two-fold: to advance the fundamental understanding of intricate quantum systems from the perspectives of quantum optics, nonlinear and many-body physics, and to provide a solid theoretical foundation for the development of emerging quantum technologies. We actively collaborate with experimental groups both at Weizmann and across the globe.

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News

January 20, 2025

Shira Barnoy Lapid, MSc student from the Chemistry Faculty, has started rotation with the group. Welcome!

January 16, 2025

A preprint on topological edge states of bound photon pairs in waveguide QED together with Jiaming Shi is now available on arXiv

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Latest Publications

Multimer states in multilevel waveguide QED

Shi J. & Poddubny A. N. (2024) Physical Review A. 110, 5, 053707.

Arxiv: 2406.12390

We study theoretically the interplay of spontaneous emission and interactions for the multiple-excited quasistationary eigenstates in a finite periodic array of multilevel atoms coupled to the waveguide. We develop an analytical approach to calculate such eigenstates based on the subradiant dimer basis. Our calculations reveal the peculiar multimerization effect driven by the anharmonicity of the atomic potential: while a general eigenstate is an entangled one, there exist eigenstates that are products of dimers, trimers, or tetramers, depending on the size of the system and the fill factor. At half-filling, these product states acquire a periodic structure with all-to-all connections inside each multimer and become the most subradiant ones.

How Single-Photon Switching is Quenched with Multiple Λ -Level Atoms

Poddubny A. N., Rosenblum S. & Dayan B. (2024) Physical Review Letters. 133, 11, 113601.

Single-photon nonlinearity, namely, the change in the response of the system as the result of the interaction with a single photon, is generally considered an inherent property of a single quantum emitter. Although the dependence on the number of emitters is well understood for the case of two-level systems, deterministic operations such as single-photon switching or photon-atom gates inherently require more complex level structures. Here, we theoretically consider single-photon switching in ensembles of emitters with a Λ-level scheme and show that the switching efficiency vanishes with the number of emitters. Interestingly, the mechanism behind this behavior is the quantum Zeno effect, manifested in a slowdown of the photon-controlled dynamics of the atomic ground states.

Mesoscopic non-Hermitian skin effect

Poddubny A., Zhong J. & Fan S. (2024) Physical Review A. 109, 6, L061501.

We discuss a generalization of the non-Hermitian skin effect to finite-size photonic structures with neither gain nor loss in the bulk and a purely real energy spectrum under periodic boundary conditions (PBCs). We show that despite being Hermitian in the bulk, such systems can still have significant portions of eigenmodes concentrated at the edges and that this edge concentration can be linked to the nontrivial point-gap topology of the size-dependent regularized PBC spectrum, accounting for the radiative losses due to photon emission through the edges. We focus on a particular example of an array of atoms chirally coupled to the waveguide, but our results are also applicable to other systems with losses through the edges.

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