Emerging Quadrature Lattices of Kerr Combs

A quadrature lattice is a coupled array of squeezed vacuum field quadratures that offers new avenues in shaping the quantum properties of multimode light [1-3]. Such lattices are described within the framework of non-Hermitian, non-dissipative physics and exhibit intriguing lattice phenomena such as lattice exceptional points, edge-states, entanglement and non-Hermitian skin effect, offering fundamentally new methods for controlling quantum fluctuations [1, 4]. Nonlinear resonators are suitable for studying multimode pair-generation processes and squeezing which are non-dissipative in χ(2) and χ(3) materials [5-12], but observing non-Hermitian lattice phenomena in photonic quadrature lattices was not achieved. Remarkably, in dissipative Kerr microcombs [13], which have revolutionized photonic technology, such lattices emerge and govern the quantum noise that leads to comb formation. Thus, they offer a unique opportunity to realize quadrature lattices, and to study and manipulate multimode quantum noise which is essential for any quantum technology. Here, we experimentally study non-Hermitian lattice effects in photonic quadrature lattices for the first time. Our photonic quadrature lattices emerge at Kerr microcomb transitions, allowing us to observe fundamental connections between dispersion symmetry, frequency-dependent squeezed supermodes, and non-Hermitian lattice physics in an integrated setup. Our work unifies two major fields, quantum non-Hermitian physics and Kerr combs, and opens the door to utilizing dissipative Kerr combs to experimentally explore rich non-Hermitian physics in the quantum regime, engineer quantum light, and develop new tools to study the quantum noise and formation of Kerr combs.