@article { WOS:000693643600008,
title = {Frustration-induced anomalous transport and strong photon decay in waveguide QED},
journal = {Phys. Rev. Res.},
volume = {3},
number = {3},
year = {2021},
month = {SEP 7},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We study the propagation of photons in a one-dimensional environment consisting of two noninteracting 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 {\textquoteleft}{\textquoteleft}dressed-spin,{{\textquoteright}{\textquoteright}} 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 interspecies interactions. Our results are relevant to state-of-the-art circuit and cavity quantum electrodynamics experiments.},
doi = {10.1103/PhysRevResearch.3.L032058},
author = {Belyansky, Ron and Whitsitt, Seth and Lundgren, Rex and Wang, Yidan and Vrajitoarea, Andrei and Houck, Andrew A. and Gorshkov, V, Alexey}
}
@article { WOS:000646178000004,
title = {Torus spectroscopy of the Gross-Neveu-Yukawa quantum field theory: Free Dirac versus chiral Ising fixed point},
journal = {Phys. Rev. B},
volume = {103},
number = {12},
year = {2021},
month = {MAR 12},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We establish the universal torus low-energy spectra at the free Dirac fixed point and at the strongly coupled chiral Ising fixed point and their subtle crossover behavior in the Gross-Neuveu-Yukawa field theory with n(D) = 4 component Dirac spinors in D = (2 + 1) dimensions. These fixed points and the field theories are directly relevant for the long-wavelength physics of certain interacting Dirac systems, such as repulsive spinless fermions on the honeycomb lattice or pi-flux square lattice. The torus energy spectrum has been shown previously to serve as a characteristic fingerprint of relativistic fixed points and is a powerful tool to discriminate quantum critical behavior in numerical simulations. Here, we use a combination of exact diagonalization and quantum Monte Carlo simulations of strongly interacting fermionic lattice models, to compute the critical torus energy spectrum on finite-size clusters with periodic boundaries and extrapolate them to the thermodynamic limit. Additionally, we compute the torus energy spectrum analytically using the perturbative expansion in epsilon = 4 - D, which is in good agreement with the numerical results, thereby validating the presence of the chiral Ising fixed point in the lattice models at hand. We show that the strong interaction between the spinor field and the scalar order-parameter field strongly influences the critical torus energy spectrum and we observe prominent multiplicity features related to an emergent symmetry predicted from the quantum field theory. Building on these results we are able to address the subtle crossover physics of the low-energy spectrum flowing from the chiral Ising fixed point to the Dirac fixed point, and analyze earlier flawed attempts to extract Fermi velocity renormalizations from the low-energy spectrum.},
issn = {2469-9950},
doi = {10.1103/PhysRevB.103.125128},
author = {Schuler, Michael and Hesselmann, Stephan and Whitsitt, Seth and Lang, Thomas C. and Wessel, Stefan and Laeuchli, Andreas M.}
}
@article {liu_circuit_2020,
title = {Circuit complexity across a topological phase transition},
journal = {Phys. Rev. Res.},
volume = {2},
number = {1},
year = {2020},
note = {Place: ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA Publisher: AMER PHYSICAL SOC Type: Article},
month = {mar},
abstract = {We use Nielsen{\textquoteright}s geometric approach to quantify the circuit complexity in a one-dimensional Kitaev chain across a topological phase transition. We find that the circuit complexities of both the ground states and nonequilibrium steady states of the Kitaev model exhibit nonanalytical behaviors at the critical points, and thus can be used to detect both equilibrium and dynamical topological phase transitions. Moreover, we show that the locality property of the real-space optimal Hamiltonian connecting two different ground states depends crucially on whether the two states belong to the same or different phases. This provides a concrete example of classifying different gapped phases using Nielsen{\textquoteright}s circuit complexity. We further generalize our results to a Kitaev chain with long-range pairing, and we discuss generalizations to higher dimensions. Our result opens up an avenue for using circuit complexity as a tool to understand quantum many-body systems.},
doi = {10.1103/PhysRevResearch.2.013323},
author = {Liu, Fangli and Whitsitt, Seth and Curtis, Jonathan B. and Lundgren, Rex and Titum, Paraj and Yang, Zhi-Cheng and Garrison, James R. and Gorshkov, V, Alexey}
}
@article { ISI:000550577700002,
title = {Real-time dynamics of string breaking in quantum spin chains},
journal = {Phys. Rev. B},
volume = {102},
number = {1},
year = {2020},
month = {JUL 21},
pages = {014308},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {String breaking is a central dynamical process in theories featuring confinement, where a string connecting two charges decays at the expense of the creation of new particle-antiparticle pairs. Here, we show that this process can also be observed in quantum Ising chains where domain walls get confined either by a symmetry-breaking field or by long-range interactions. We find that string breaking occurs, in general, as a two-stage process. First, the initial charges remain essentially static and stable. The connecting string, however, can become a dynamical object. We develop an effective description of this motion, which we find is strongly constrained. In the second stage, which can be severely delayed due to these dynamical constraints, the string finally breaks. We observe that the associated timescale can depend crucially on the initial separation between domain walls and can grow by orders of magnitude by changing the distance by just a few lattice sites. We discuss how our results generalize to one-dimensional confining gauge theories and how they can be made accessible in quantum simulator experiments such as Rydberg atoms or trapped ions.},
issn = {2469-9950},
doi = {10.1103/PhysRevB.102.014308},
author = {Verdel, Roberto and Liu, Fangli and Whitsitt, Seth and Gorshkov, V, Alexey and Heyl, Markus}
}
@article { ISI:000449780400004,
title = {Quantum field theory for the chiral clock transition in one spatial dimension},
journal = {PHYSICAL REVIEW B},
volume = {98},
number = {20},
year = {2018},
month = {NOV 9},
pages = {205118},
issn = {2469-9950},
doi = {10.1103/PhysRevB.98.205118},
author = {Whitsitt, Seth and Samajdar, Rhine and Sachdev, Subir}
}