Freiburg 2024 – scientific programme

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SYAD: Symposium SAMOP Dissertation Prize 2024

SYAD 1: SAMOP Dissertation Prize

SYAD 1.4: Invited Talk

Monday, March 11, 2024, 16:00–16:30, Paulussaal

Non-Hermitian topology and directional amplification — •Clara Wanjura — Max Planck Institute for the Science of Light, Erlangen, Germany

Topology has been a major research theme in condensed matter physics and is associated with a number of remarkable phenomena such as robust edge states. A prominent example is the quantum Hall effect, in which the topological invariant is directly observable through the Hall resistance. More recently, topology started to be investigated in systems experiencing gain and loss sparking the field of non-Hermitian topology. However, so far, a clear observable signature of non-Hermitian topology had been lacking.

In this talk, I will show that non-trivial, non-Hermitian topology is in one-to-one correspondence with the phenomenon of directional amplification in one-dimensional bosonic systems, e.g., cavity arrays. Directional amplification allows to selectively amplify signals depending on their propagation direction and has attracted much attention as key resource for applications, such as quantum information processing. Remarkably, in non-trivial topological phases, the end-to-end gain grows exponentially with the number of sites. Furthermore, this effect is robust against disorder with the amount of tolerated disorder given by the separation between the complex spectrum and the origin. Our work opens up new routes for the design of multimode robust directional amplifiers and sensors based on non-Hermitian topology that can be integrated in scalable platforms such as superconducting circuits, optomechanical systems and nanocavity arrays.

Keywords: non-reciprocity and directional amplification; non-Hermitian topology; reservoir engineering; driven-dissipative quantum systems; cavity arrays