Xueyue Zhang

A scalable superconducting quantum simulator with long-range connectivity based on a photonic bandgap metamaterial

  1. Xueyue Zhang,
  2. Eunjong Kim,
  3. Daniel K. Mark,
  4. Soonwon Choi,
  5. and Oskar Painter
Synthesis of many-body quantum systems in the laboratory can provide further insight into the emergent behavior of quantum materials. While the majority of engineerable many-body systems,
or quantum simulators, consist of particles on a lattice with local interactions, quantum systems featuring long-range interactions are particularly difficult to model and interesting to study due to the rapid spatio-temporal growth of entanglement in such systems. Here we present a scalable quantum simulator architecture based on superconducting transmon qubits on a lattice, with interactions mediated by the exchange of photons via a metamaterial waveguide quantum bus. The metamaterial waveguide enables extensible scaling of the system and multiplexed qubit read-out, while simultaneously protecting the qubits from radiative decay. As an initial demonstration of this platform, we realize a 10-qubit simulator of the one-dimensional Bose-Hubbard model, with in situ tunability of both the hopping range and the on-site interaction. We characterize the Hamiltonian of the system using a measurement-efficient protocol based on quantum many-body chaos, uncovering the remnant phase of Bloch waves of the metamaterial bus in the long-range hopping terms. We further study the many-body quench dynamics of the system, revealing through global bit-string statistics the predicted crossover from integrability to ergodicity as the hopping range is extended beyond nearest-neighbor. Looking forward, the metamaterial quantum bus may be extended to a two-dimensional lattice of qubits, and used to generate other spin-like lattice interactions or tailored lattice connectivity, expanding the accessible Hamiltonians for analog quantum simulation using superconducting quantum circuits.
arxiv pdf

Quantum electrodynamics in a topological waveguide

  1. Eunjong Kim,
  2. Xueyue Zhang,
  3. Vinicius S. Ferreira,
  4. Jash Banker,
  5. Joseph K. Iverson,
  6. Alp Sipahigil,
  7. Miguel Bello,
  8. Alejandro Gonzalez-Tudela,
  9. Mohammad Mirhosseini,
  10. and Oskar Painter
While designing the energy-momentum relation of photons is key to many linear, non-linear, and quantum optical phenomena, a new set of light-matter properties may be realized by employing
the topology of the photonic bath itself. In this work we investigate the properties of superconducting qubits coupled to a metamaterial waveguide based on a photonic analog of the Su-Schrieffer-Heeger model. We explore topologically-induced properties of qubits coupled to such a waveguide, ranging from the formation of directional qubit-photon bound states to topology-dependent cooperative radiation effects. Addition of qubits to this waveguide system also enables direct quantum control over topological edge states that form in finite waveguide systems, useful for instance in constructing a topologically protected quantum communication channel. More broadly, our work demonstrates the opportunity that topological waveguide-QED systems offer in the synthesis and study of many-body states with exotic long-range quantum correlations.
arxiv pdf