From Optics to Photonics

Christiana Varnava

Efficient conversion between microwave and optical photons is important for the development of hybrid quantum platforms in which quantum information is processed by superconducting circuits and transmitted with optical photons. A promising approach is to use electro-optic modulation with a microwave cavity coupled to an optical cavity, where microwave photons are up-converted to optical photons through sum frequency generation, and optical photons are converted to microwave photons through difference frequency generation. However, the frequency matching conditions in such set-ups usually require the size of the device to be large enough so that the optical frequencies of the pump and signal photons are supported. Hong Tang and colleagues have now fabricated a hybrid superconducting–photonic device that overcomes this limitation by using an integrated planar geometry to coherently convert between microwave and optical photons. adapted under a Creative Commons license CC BY-NC 4.0 ; AAAS

Mustafa A. G. Abushagur

E. Petrovskaya

Xi-Wang Luo, Xingxiang Zhou, Jin‐Shi Xu +4 more

All-optical photonic devices are crucial for many important photonic technologies and applications, ranging from optical communication to quantum information processing. Conventional design of all-optical devices is based on photon propagation and interference in real space, which may rely on large numbers of optical elements, and the requirement of precise control makes this approach challenging. Here we propose an unconventional route for engineering all-optical devices using the photon's internal degrees of freedom, which form photonic crystals in such synthetic dimensions for photon propagation and interference. We demonstrate this design concept by showing how important optical devices such as quantum memory and optical filters can be realized using synthetic orbital angular momentum (OAM) lattices in degenerate cavities. The design route utilizing synthetic photonic lattices may significantly reduce the requirement for numerous optical elements and their fine tuning in conventional design, paving the way for realistic all-optical photonic devices with novel functionalities.

Karl A. Stetson

Mihir Khanna, Yang Hu, Thomas P. Purdy

We present a resonant electro-optic transducer for efficient conversion between microwave and telecom wavelength photons. Our platform employs a bulk lithium niobate crystal whose large dielectric constant creates wavelength-scale confinement of microwave photons. By incorporating this crystal within a high-finesse Fabry - Perot optical cavity, microwave photons couple to optical photons through the electro-optic effect. We demonstrate the ability to tune our system into triply resonant operation, where microwave photons, optical pump photons, and upconverted optical photons are simultaneously resonant with high quality factor electromagnetic modes of the system. The device achieves photon number conversion efficiency at the percent level, comparable to state-of-the-art devices at room temperature -- sufficient to resolve the thermal occupation of the microwave mode -- while avoiding the noise and loss associated with metal electrodes. These results establish our all-dielectric devices as a promising platform for high-precision sensing of optically detected microwave fields and as a viable route toward single-photon-level microwave - optical quantum transduction.