Cavity Quantum Electro Optics: Microwave photonics with nonclassical states

Optical photons propagate with ultra-low loss and do not interact easily which makes them perfect information carriers. Logical operations and sensing on the other hand rely on nonlinearities and strong interactions.

GHz clock speed electrical circuits are used for computing and wireless receivers a frequency range where also some of the most promising solid-state quantum devices, such as superconducting circuits and semiconductor spin qubits, operate and interact.

The field of microwave photonics combines these two domains of the electromagnetic spectrum with a diverse set of applications ranging from radar and satellite communication, to radio-over-fiber and remote sensing. At the quantum level however, no equivalent technology exists.

This is particularly problematic because quantum systems rely on analog information exchange in a low-noise environment.

Microwave quantum circuits so far are restricted to operate inside an isolated space at millikelvin temperatures.Building on our modular electro-optic platform - the lowest noise microwave-optical interconnect to date - cQEO will realize a remarkable set of new experiments that were not possible before: Heralded entanglement and teleportation of long-lived qubit states over kilometers of fiber, synthesis of optical cat states from microwave cats, photonic control and readout of superconducting circuits, as well as photonic masing and RF sensing below the standard quantum limit.

Pushing towards higher electro-optic cooperativities will open up the rich physics known from cavity optomechanics, except now it is the readily accessible microwave field that experiences dynamical and quantum back-action rather than a mechanical mode.

This is a new physical limit akin to nonlinear optics that was predicted a decade ago but never realized.cQEO aims to uncover the full range of new physics offered by high quantum cooperativity electro-optics combined with the unique capabilities of circuit quantum electrodynamics.