Topological bosonic states via squeezing

There is enormous interest in engineering topological photonic systems, where topological protection guarantees the existence of robust edge modes. Most works in this field amount to replicating a well-known fermionic single-particle Hamiltonian. We recently studied a class of systems where this correspondence fails. Here, topology is induced by coherent two-photon driving (i.e. parametric driving). While these systems have a Hamiltonian resembling that of a fermionic topological superconductor, the bosonic physics is completely different. In particular, the topologically-protected edge states can act as frequency-converting channels, and can even serve as quantum-limited amplifiers and squeezed light sources. It is even possible to construct bosonic systems that are reminiscent of the fermionic Kitaev-Majorana chain.

Nature Communications, 2016

Phys. Rev. X, 2016

Phys. Rev. X, 2018

Enhanced light-matter interactions via two-photon driving

We show how two-photon (or parametric) driving can be used to enhance the basic light-matter interaction in a generic cavity QED system, where a two-level atom (or qubit) interacts with photons in a cavity. Driving thus enables a weakly interacting system to behave like a strongly interacting one, and even allows one to reach so-called "ultra-strong" coupling regimes. Applications include the efficient production of highly entangled Schrodinger-cat style states. The effects we predict could be realized in a number of experimental platforms, including with superconducting quantum circuits.

Phys. Rev. Lett., 2018