Yang monopoles and emergent three-dimensional topological defects in interacting bosons

Yang monopole as a zero-dimensional topological defect has been well established in multiple fields in physics. However, it remains an intriguing question to understand interaction effects on Yang monopoles. Here, we show that collective motions of many interacting bosons give rise to exotic topological defects that are distinct from Yang monopoles seen by a single particle. Whereas interactions may distribute Yang monopoles in the parameter space or glue them to a single giant one of multiple charges, three-dimensional topological defects also arise from continuous manifolds of degenerate many-body eigenstates. Their projections in lower dimensions lead to knotted nodal lines and nodal rings. Our results suggest that ultracold bosonic atoms can be used to create emergent topological defects and directly measure topological invariant that are not easy to access in solids.Comment: 6 pages (2 figures) + 7 pages (2 figures); accepted draft; fixed link

High coherent solid-state qubit from a pair of quantum dots

In this letter we propose a scheme to build up high coherent solid-state quantum bit (qubit) from two coupled quantum dots. Quantum information is stored in electron-hole pair state with the electron and hole locating in different dots, and universal quantum gates involving any pair of qubits are realized by effective coupling interaction via virtually exchanging cavity photons.Comment: 3 pages, 1 figur