Andreas Nunnenkamp (Vienna): Novel Platforms for Quantum Science and Technology

The 'second quantum revolution' aims at exploiting coherence for noveltechnologies that will likely involve electromagnetic, mechanical, atomic, andtopological degrees of freedom. Directional amplifiers, that amplify signalsdepending on the propagation direction, have recently attracted muchattention, also for applications in quantum technologies. Here, I will present aunifying framework based on topology to understand non-reciprocity anddirectional amplification in driven-dissipative cavity arrays. Specifically, I willdiscuss a one-to-one correspondence between a non-zero topological invariantdefined on the spectrum of the dynamic matrix and regimes of directionalamplification, in which the end-to-end gain grows exponentially with thenumber of cavities. Time-permitting, I will give a brief overview on our work onhigher-order and fractional discrete time crystals in quantum and classical spinarrays.