Speaker: 
Andreas Nunnenkamp - Univ. Wien

Title: 
Directional amplification and non-Hermitian topology

Abstract:
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 then show that this correspondence also holds in the presence of disorder as long as the size of the point gap is larger than the disorder. Finally, I will show how to restore the bulk-boundary correspondence for one paradigmatic class of non-Hermitian Hamiltonians. Our work opens up new avenues in topological photonics and non-Hermitian phases of matter.

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QuCoLiMa Talks are regular seminars of the collaborative research center TRR 306 QuCoLiMa (Quantum Cooperativity of Light and Matter), where (external) experts are invited to present their work.

More information at www.qucolima.de/talks