Cavity quantum matter

     Physicists have observed in a variety of scenarios that the spontaneous emission rate of a quantum dipole depends on its photonic environment. This phenomenon is named the Purcell effect and can be derived from rigorous mathematical grounds by the Fermi's golden rule. In recent years, intense efforts have been made to fabricate hybrid quantum systems that incorporate solid-state materials and photonic cavities in a single device platform. These cavity quantum electrodynamic (QED) systems are born out of the same idea that underlies Purcell effect in that they leverage photonic density-of-states engineering, but have readily gone beyond it since the interaction of solid-state excitations with cavity light fields may exceed the Purcell limit by orders of magnitude. This opens up the possibility for studying the previously uncharted territories of cavity QED such as the ultrastrong coupling regime, which is defined as the light-matter coupling rate approaching the fundamental excitation frequency itself.
  We design and fabricate photonic cavity structures and embed solid-state materials in them, thereby constructing hybrid quantum devices. Our objective is to investigate unusual consequences of ultrastrong light-matter coupling, such as the possible emergence of novel light-matter entangled orders of polaritons, those are, quasiparticles formed by electrons dressed by cavity photons. Further, we are interested in exploring the possibility of engineering the ground states of solids by tailoring the cavity vacuum. When light-matter interaction is strong, it is predicted that even the vacuum photons that appear due to quantum mechanical fluctuations can significantly alter the materials' ground state. This would tremendously enrich the strategy for nonthermal light-control of solids, by exposing materials to engineered quantum vacuum fluctuations without the need to shine any light.

 

Selected publications of our work in this area:

• Nat. Photon. 12, 324 (2018).

• Nat. Photon. 12, 362 (2018).

• Nat. Phys. 12, 1005 (2016).

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