Preserving the quantum coherence of signals is of paramount importance for components utilized in quantum information processing, quantum computation and quantum measurement setups. In recent years a tremendous progress has been made in the development of quantum-limited components, such as reciprocal and nonreciprocal amplifiers, circulators and isolators. A promising way to design these devices is based on parametric modulation of coupled modes, where the required mode-mixing processes are realized by utilizing Josphson junction-based tunable couplers or via coupling to mechanical degrees of freedom. All designs come with their unique challenges, such as higher-order nonlinearities – limiting the dynamical range, or high thermal occupations – leading to noise contamination of the signal. In addition, standard cavity-based parametric amplifiers suffer from a fixed gain-bandwidth product.
In this talk we present possible ways to face these challenges, complemented with an introduction of the basic concept on how to engineer nonreciprocal interactions and devices based on balancing a coherent interaction with the corresponding dissipative interaction. Furthermore, we present possible implementations in superconducting circuit and optomechanical architectures and discuss routes for optimizing the design of microwave circuits enabling nonreciprocal and reciprocal amplification at the quantum limit.
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Anja Metelmann is a Emmy Noether research group leader at the Department of Theoretical Physics at the Free University Berlin in Germany. In 2012, she received her PhD in Physics from the Technical University Berlin in Germany, under the supervision of Prof. Tobias Brandes. She spend her postdoctral time in the group of Prof. Aashish Clerk at the Physics Department of McGill University in Montreal and in the group of Prof. Hakan Tureci at the Department of Electrical Engineering at Princeton University. Anja Metelmann’s research interests lay in the fundamental aspects and applications of superconducting circuits and mechanical systems in the quantum regime. Her current research focuses on the theory of nonreciprocal photon propagation in open quantum systems via reservoir engineering.