Symmetry-breaking transitions are a well-understood phenomenon of closed quantum systems in quantum optics, condensed matter, and high energy physics. However, symmetry breaking in open systems is less thoroughly understood, in part due to the richer steady-state and symmetry structure that such systems possess. For the prototypical open system{\textemdash}a Lindbladian{\textemdash}a unitary symmetry can be imposed in a {\textquotedblleft}weak{\textquotedblright} or a {\textquotedblleft}strong{\textquotedblright} way. We characterize the possible\ Zn\ symmetry-breaking transitions for both cases. In the case of\ Z2, a weak-symmetry-broken phase guarantees at most a classical bit steady-state structure, while a strong-symmetry-broken phase admits a partially protected steady-state qubit. Viewing photonic cat qubits through the lens of strong-symmetry breaking, we show how to dynamically recover the logical information after any gap-preserving strong-symmetric error; such recovery becomes perfect exponentially quickly in the number of photons. Our study forges a connection between driven-dissipative phase transitions and error correction.

}, doi = {10.1103/PhysRevLett.125.240405}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.125.240405}, author = {Lieu, Simon and Belyansky, Ron and Young, Jeremy T. and Lundgren, Rex and Albert, Victor V. and Gorshkov, Alexey V.} } @article {ISI:000464756500001, title = {Confined Quasiparticle Dynamics in Long-Range Interacting Quantum Spin Chains}, journal = {Phys. Rev. Lett.}, volume = {122}, number = {15}, year = {2019}, month = {APR 16}, pages = {150601}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We study the quasiparticle excitation and quench dynamics of the one-dimensional transverse-field Ising model with power-law (1/r(alpha)) interactions. We find that long-range interactions give rise to a confining potential, which couples pairs of domain walls (kinks) into bound quasiparticles, analogous to mesonic states in high-energy physics. We show that these quasiparticles have signatures in the dynamics of order parameters following a global quench, and the Fourier spectrum of these order parameters can be exploited as a direct probe of the masses of the confined quasiparticles. We introduce a two-kink model to qualitatively explain the phenomenon of long-range-interaction-induced confinement and to quantitatively predict the masses of the bound quasiparticles. Furthermore, we illustrate that these quasiparticle states can lead to slow thermalization of one-point observables for certain initial states. Our work is readily applicable to current trapped-ion experiments.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.122.150601}, author = {Liu, Fangli and Lundgren, Rex and Titum, Paraj and Pagano, Guido and Zhang, Jiehang and Monroe, Christopher and Gorshkov, V, Alexey} } @article { ISI:000457704900001, title = {Interacting Qubit-Photon Bound States with Superconducting Circuits}, journal = {PHYSICAL REVIEW X}, volume = {9}, number = {1}, year = {2019}, month = {FEB 1}, pages = {011021}, issn = {2160-3308}, doi = {10.1103/PhysRevX.9.011021}, author = {Sundaresan, Neereja M. and Lundgren, Rex and Zhu, Guanyu and Gorshkov, V, Alexey and Houck, Andrew A.} } @article { ISI:000502782600002, title = {Momentum-space entanglement after a quench in one-dimensional disordered fermionic systems}, journal = {Phys. Rev. B}, volume = {100}, number = {24}, year = {2019}, month = {DEC 13}, pages = {241108}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We numerically investigate the momentum-space entanglement entropy and entanglement spectrum of the random-dimer model and its generalizations, which circumvent Anderson localization, after a quench in the Hamiltonian parameters. The type of dynamics that occurs depends on whether or not the Fermi level of the initial state is near the energy of the delocalized states present in these models. If the Fermi level of the initial state is near the energy of the delocalized states, we observe an interesting slow logarithmiclike growth of the momentum-space entanglement entropy followed by an eventual saturation. Otherwise, the momentum-space entanglement entropy is found to rapidly saturate. We also find that the momentum-space entanglement spectrum reveals the presence of delocalized states in these models for long times after the quench and the many-body entanglement gap decays logarithmically in time when the Fermi level is near the energy of the delocalized states.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.100.241108}, author = {Lundgren, Rex and Liu, Fangli and Laurell, Pontus and Fiete, Gregory A.} } @article {10546, title = {Fractional Quantum Hall Phases of Bosons with Tunable Interactions: From the Laughlin Liquid to a Fractional Wigner Crystal}, journal = {Phys. Rev. Lett.}, volume = {121}, year = {2018}, month = {Dec}, pages = {253403}, doi = {10.1103/PhysRevLett.121.253403}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.121.253403}, author = {Gra{\ss}, Tobias and Bienias, Przemyslaw and Gullans, Michael J. and Lundgren, Rex and Maciejko, Joseph and Gorshkov, Alexey V.} }