Mengmeng Li

Demonstration of Hopf-link semimetal bands with superconducting circuits

  1. Xinsheng Tan,
  2. Mengmeng Li,
  3. Danyu Li,
  4. Kunzhe Dai,
  5. Haifeng Yu,
  6. and Yang Yu
Hopf-link semimetals exhibit exotic gapless band structures with fascinating topological properties, which have never been observed in nature. Here we demonstrated nodal lines with
topological form of Hopf-link chain in artificial semimetal-bands. Driving superconducting quantum circuits with elaborately designed microwave fields, we mapped the momentum space of a lattice to the parameter space, realizing the Hamiltonian of a Hopf-link semimetal. By measuring the energy spectrum, we directly imaged nodal lines in cubic lattices. By tuning the driving fields we adjusted various parameters of Hamiltonian. Important topological features, such as link-unlink topological transition and the robustness of Hopf-link chain structure are investigated. Moreover, we extracted linking number by detecting Berry phase associated with different loops enclosing or disclosing nodal lines. The topological invariant clearly reveals the scenery of the connection between two nodal rings. Our simulations provide foremost knowledge for developing new materials and quantum devices.
arxiv pdf

Extensible 3D architecture for superconducting quantum computing

  1. Qiang Liu,
  2. Mengmeng Li,
  3. Kunzhe Dai,
  4. Ke Zhang,
  5. Guangming Xue,
  6. Xinsheng Tan,
  7. Haifeng Yu,
  8. and Yang Yu
Using a multi-layered printed circuit board, we propose a 3D architecture suitable for packaging supercon- ducting chips, especially chips that contain two-dimensional qubit arrays.
In our proposed architecture, the center strips of the buried coplanar waveguides protrude from the surface of a dielectric layer as contacts. Since the contacts extend beyond the surface of the dielectric layer, chips can simply be flip-chip packaged with on-chip receptacles clinging to the contacts. Using this scheme, we packaged a multi-qubit chip and per- formed single-qubit and two-qubit quantum gate operations. The results indicate that this 3D architecture provides a promising scheme for scalable quantum computing.
arxiv pdf