We study many-body optical phenomena arising in ensembles of atoms or other quantum emitters. When emitters decay into a common bath, dissipative interactions generate correlations and entanglement between them. This is the perfect playground for observing the physics that we are interested in: a combination of complexity, emergence, dissipation, long-range interactions, and non-linearity. Please see below for a more detailed description of our research interests.

Quantum optics in atomic arrays

In dense and ordered atomic arrays, strong constructive or destructive interference of light emitted by excited atoms can give rise to exotic phenomena, which have no counterpart in disordered atomic gases. Arrays potentially also comprise a powerful new platform for quantum optics. Interference in photon emission gives rise to the emergence of dark (subradiant) states, with extremely long lifetimes, which can be of use in applications in quantum information science, sensing, and metrology. We are interested in understanding both the single-excitation and many body properties of highly-correlated dark states in ordered and disordered arrays of different dimensionality and topology. We also investigate potential applications of correlated dissipation in the areas of quantum information science, nonlinear optics, and metrology. For references on these topics, please click herehere and here. This physics also occurs in other kinds of systems. Recently we have been exploring subradiant effects involving superconducting qubits coupled through a common transmission line. For details, click here.

The figure in the right shows the physics of subradiant single-excitation states of one-dimensional atomic arrays: (a) Decay rate of the most subradiant eigenstate vs. atom number N, for different lattice constants, normalized to the resonance wavelength. The continuous lines are guides to the eye and scale as ∼1/N3. (b) Field intensity emitted by the most subradiant mode in a chain of N = 50 atoms. The field is largely evanescent transverse to the bulk of the chain, while most of the energy is radiated out through scattering at the ends of the chain, as expected for an optical waveguide. Red circles denote atomic positions.

Quantum optics in non-traditional baths

Photon-mediated interactions can be modified by placing atoms in different dielectric environments, such as cavities, waveguides, and photonic crystals. For instance, photonic crystals – periodically modulated dielectric structures – display a bandgap in which light cannot propagate. This switches off dissipation through the photonic guided mode, making the interaction between atoms purely coherent (if one neglects dissipation into free space). This makes photonic crystals suitable platforms for quantum simulation, as well as fascinating atom-light interfaces. We are interested in expanding the quantum optics theoretical toolbox and guide state of the art experiments in this area. To read about our theory work describing how to understand atom-atom interactions in the presence of complex dielectrics, using the electromagnetic Green’s function, click here. For recent collaboration work with experimentalists, involving atoms in photonic crystals and superconducting qubits in transmission lines, click here, and here.

We regularly partner up with leading experimental groups at Columbia and other universities. We currently collaborate with the group of Prof. Jeff Kimble at Caltech, and the groups of Profs. Michal Lipson, Sebastian Will, Nanfang Yu, and Alex Gaeta at Columbia.