Alexander Poddubny Group

Research

Recent preprints on arXiv Google Scholar

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

December 4, 2025

Just a group photo!

October 22, 2025

New preprint with Gad Horovitz

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Latest Publications

van der Waals materials for waveguide QED

Poddubny A. (2025) Nature Photonics. 19, 8, p. 783-784

Topological Nature of Edge States for One-Dimensional Systems without Symmetry Protection

Zhong J., Wang H., Poddubny A. N. & Fan S. (2025) Physical Review Letters. 135, 1, 016601.

We numerically verify and analytically prove a winding number invariant that correctly predicts the number of edge states in one-dimensional, nearest-neighbor (between unit cells), two-band models with any complex couplings and open boundaries. Our winding number uses analytical continuation of the wave-vector into the complex plane and involves two special points on the full Riemann surface band structure that correspond to bulk eigenvector degeneracies. Our winding number is invariant under unitary or similarity transforms. We emphasize that the topological criteria we propose here differ from what is traditionally defined as a topological or trivial phase in symmetry-protected classification studies. It is a broader invariant for our model that supports non-zero energy edge states and its transition does not coincide with the gap closing condition. When the relevant symmetries are applied, our invariant reduces to well-known Hermitian and non-Hermitian symmetry-protected topological invariants.

Chiral Dissociation of Bound Photon Pairs for a Non-Hermitian Skin Effect

Shi J. & Poddubny A. N. (2025) Physical Review Letters. 134, 23, p. 233602 233602.

We theoretically study the bound states of interacting photons propagating in a waveguide chirally coupled to an array of atoms. We demonstrate that the bound photon pairs can concentrate at the edge of the array and link this to the non-Hermitian skin effect. Unlike tight-binding non-Hermitian setups, the bound states in the waveguide-coupled array exhibit infinite radiative lifetimes when the array has an infinite size. However, in a finite array, non-Hermiticity and localization of bound pairs emerge due to their chiral dissociation into scattering states. Counterintuitively, when the photons are preferentially emitted to the right, the bound pairs are localized at the left edge of the array and vice versa.

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