@article {2760, title = {Universality in one-dimensional scattering with general dispersion relations}, journal = {Phys. Rev. Res.}, volume = {4}, year = {2022}, month = {3/17/2021}, chapter = {023014}, abstract = {

Many synthetic quantum systems allow particles to have dispersion relations that are neither linear nor quadratic functions. Here, we explore single-particle scattering in one dimension when the dispersion relation is ϵ(k)=\±|d|km, where m\≥2 is an integer. We study impurity scattering problems in which a single-particle in a one-dimensional waveguide scatters off of an inhomogeneous, discrete set of sites locally coupled to the waveguide. For a large class of these problems, we rigorously prove that when there are no bright zero-energy eigenstates, the S-matrix evaluated at an energy E\→0 converges to a universal limit that is only dependent on m. We also give a generalization of a key index theorem in quantum scattering theory known as Levinson\&$\#$39;s theorem -- which relates the scattering phases to the number of bound states -- to impurity scattering for these more general dispersion relations.

}, doi = {https://doi.org/10.48550/arXiv.2103.09830}, url = {https://arxiv.org/abs/2103.09830}, author = {Yidan Wang and Michael Gullans and Xuesen Na and Alexey V. Gorshkov} } @article {2762, title = {Frustration-induced anomalous transport and strong photon decay in waveguide QED}, journal = {Phys. Rev. Research}, volume = {3}, year = {2021}, month = {9/16/2021}, abstract = {

We study the propagation of photons in a one-dimensional environment consisting of two non-interacting species of photons frustratingly coupled to a single spin-1/2. The ultrastrong frustrated coupling leads to an extreme mixing of the light and matter degrees of freedom, resulting in the disintegration of the spin and a breakdown of the \"dressed-spin\", or polaron, description. Using a combination of numerical and analytical methods, we show that the elastic response becomes increasingly weak at the effective spin frequency, showing instead an increasingly strong and broadband response at higher energies. We also show that the photons can decay into multiple photons of smaller energies. The total probability of these inelastic processes can be as large as the total elastic scattering rate, or half of the total scattering rate, which is as large as it can be. The frustrated spin induces strong anisotropic photon-photon interactions that are dominated by inter-species interactions. Our results are relevant to state-of-the-art circuit and cavity quantum electrodynamics experiments.

}, doi = {https://doi.org/10.1103/PhysRevResearch.3.L032058}, url = {https://arxiv.org/abs/2007.03690}, author = {Ron Belyansky and Seth Whitsitt and Rex Lundgren and Yidan Wang and Andrei Vrajitoarea and Andrew A. Houck and Alexey V. Gorshkov} } @article {2568, title = {On-demand indistinguishable single photons from an efficient and pure source based on a Rydberg ensemble}, year = {2020}, month = {3/4/2020}, abstract = {

Single photons coupled to atomic systems have shown to be a promising platform for developing quantum technologies. Yet a bright on-demand, highly pure and highly indistinguishable single-photon source compatible with atomic platforms is lacking. In this work, we demonstrate such a source based on a strongly interacting Rydberg system. The large optical nonlinearities in a blockaded Rydberg ensemble convert coherent light into a single-collective excitation that can be coherently retrieved as a quantum field. We observe a single-transverse-mode efficiency up to 0.18(2), g(2)=2.0(1.5)\×10\−4, and indistinguishability of 0.982(7), making this system promising for scalable quantum information applications. Accounting for losses, we infer a generation probability up to 0.40(4). Furthermore, we investigate the effects of contaminant Rydberg excitations on the source efficiency. Finally, we introduce metrics to benchmark the performance of on-demand single-photon sources.\ 

}, url = {https://arxiv.org/abs/2003.02202}, author = {Dalia P. Ornelas-Huerta and Alexander N. Craddock and Elizabeth A. Goldschmidt and Andrew J. Hachtel and Yidan Wang and P. Bienias and Alexey V. Gorshkov and Steve L. Rolston and James V. Porto} } @article {2681, title = {Resonant enhancement of three-body loss between strongly interacting photons}, year = {2020}, month = {10/19/2020}, abstract = {

Rydberg polaritons provide an example of a rare type of system where three-body interactions can be as strong or even stronger than two-body interactions. The three-body interactions can be either dispersive or dissipative, with both types possibly giving rise to exotic, strongly-interacting, and topological phases of matter. Despite past theoretical and experimental studies of the regime with dispersive interaction, the dissipative regime is still mostly unexplored. Using a renormalization group technique to solve the three-body Schr{\"o}dinger equation, we show how the shape and strength of dissipative three-body forces can be universally enhanced for Rydberg polaritons. We demonstrate how these interactions relate to the transmission through a single-mode cavity, which can be used as a probe of the three-body physics in current experiment

}, url = {https://arxiv.org/abs/2010.09772}, author = {Marcin Kalinowski and Yidan Wang and Przemyslaw Bienias and Michael Gullans and Dalia P. Ornelas-Huerta and Alexander N. Craddock and Steven L. Rolston and J. V. Porto and Hans Peter B{\"u}chler and Alexey V. Gorshkov} } @article {2609, title = {Transport and dynamics in the frustrated two-bath spin-boson model}, year = {2020}, month = {7/7/2020}, abstract = {

We study the strong coupling dynamics as well as transport properties of photons in the two-bath spin-boson model, in which a spin-1/2 particle is frustratingly coupled to two independent Ohmic bosonic baths. Using a combination of numerical and analytical methods, we show that the frustration in this model gives rise to rich physics in a very wide range of energies. This is in contrast to the one-bath spin-boson model, where the non-trivial physics occurs at an energy scale close to the renormalized spin frequency. The renormalized spin frequency in the two-bath spin-boson model is still important, featuring in different observables, including the non-equiblirum dynamics of both the spin and the baths along with the elastic transport properties of a photon. The latter however reveals a much more complex structure. The elastic scattering displays non-monotonic behavior at high frequencies, and is very different in the two channels: intra- and inter-bath scattering. The photon can also be inelastically scattered, a process in which it is split into several photons of smaller energies. We show that such inelastic processes are highly anisotropic, with the outgoing particles being preferentially emitted into only one of the baths. Moreover, the inelastic scattering rate is parameterically larger than in the one-bath case, and can even exceed the total elastic rate. Our results can be verified with state-of-the-art circuit and cavity quantum electrodynamics experiments.\ 

}, url = {https://arxiv.org/abs/2007.03690}, author = {Ron Belyansky and Seth Whitsitt and Rex Lundgren and Yidan Wang and Andrei Vrajitoarea and Andrew A. Houck and Alexey V. Gorshkov} } @article {2516, title = {Beyond Spontaneous Emission: Giant Atom Bounded in Continuum}, year = {2019}, month = {12/20/2019}, abstract = {

The quantum coupling of individual superconducting qubits to microwave photons leads to remarkable experimental opportunities. Here we consider the phononic case where the qubit is coupled to an electromagnetic surface acoustic wave antenna that enables supersonic propagation of the qubit oscillations. This can be considered as a giant atom that is many phonon wavelengths long. We study an exactly solvable toy model that captures these effects, and find that this non-Markovian giant atom has a suppressed relaxation, as well as an effective vacuum coupling between a qubit excitation and a localized wave packet of sound, even in the absence of a cavity for the sound waves. Finally, we consider practical implementations of these ideas in current surface acoustic wave devices.\ 

}, url = {https://arxiv.org/abs/1912.09980}, author = {Shangjie Guo and Yidan Wang and Thomas Purdy and J. M. Taylor} } @article {2213, title = {Single-photon bound states in atomic ensembles}, year = {2018}, abstract = {

We illustrate the existence of single-excitation bound states for propagating photons interacting with N two-level atoms. These bound states can be calculated from an effective spin model, and their existence relies on dissipation in the system. The appearance of these bound states is in a one-to-one correspondence with zeros in the single-photon transmission and with divergent bunching in the second-order photon-photon correlation function. We also formulate a dissipative version of Levinson\&$\#$39;s theorem for this system by looking at the relation between the number of bound states and the winding number of the transmission phases. This theorem allows a direct experimental measurement of the number of bound states using the measured transmission phases.

}, url = {https://arxiv.org/abs/1809.01147}, author = {Yidan Wang and Michael Gullans and Antoine Browaeys and J. V. Porto and Darrick E. Chang and Alexey V. Gorshkov} }