TRR 360 Seminar:

Directional amplification, non-Hermitian topology, and optomechanical realisation of the bosonic Kitaev chain

Andreas Nunnenkamp

Directional amplification, in which signals are selectively amplified depending on their propagation direction, has attracted much attention as a key resource for applications, including quantum information processing. I will present a unifying framework based on non-Hermitian topology to understand non-reciprocity and directional amplification in driven-dissipative cavity arrays. Specifically, I will unveil a one-to-one correspondence between a non-zero topological invariant defined on the spectrum of the dynamic matrix and regimes of directional amplification, in which the end-to-end gain grows exponentially with the number of cavities. I will show how to restore the bulk-boundary correspondence for one paradigmatic class of non-Hermitian Hamiltonians. Finally, I will present experiments on a bosonic analog of the fermionic Kitaev chain in an nano-optomechanical network. Our work opens up new avenues in topological photonics and non-Hermitian phases of matter.

 

C.C. Wanjura, M. Brunelli, and A. Nunnenkamp,

Topological framework for directional amplification in driven-dissipative cavity arrays,

Nat Commun 11, 3149 (2020).

 

M. Brunelli, C.C. Wanjura, and A. Nunnenkamp,

Restoration of the non-Hermitian bulk-boundary correspondence via topological amplification,

SciPost Phys. 15, 173 (2023).

 

J.J. Slim, C.C. Wanjura, M. Brunelli et al.,

Optomechanical realization of the bosonic Kitaev chain,

Nature 627, 767 (2024).