Characterization of Quantum Interconnects

Chiao-Hsuan Wang^1,2,3*

¹Department of Physics and Center for Theoretical Physics, National Taiwan University, Taipei, Taiwan
²Center for Quantum Science and Engineering, National Taiwan University, Taipei, Taiwan
³Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan

* Presenter:Chiao-Hsuan Wang, email:chiaowang@phys.ntu.edu.tw

High-performance quantum transducers, devices that interconnect disparate physical systems for coherent information conversion, are essential in quantum science and technology. To construct large-scale quantum networks, quantum transduction between optical frequencies, ideal for low-loss transmission across long distances, and microwave frequencies, which admit high-fidelity quantum operations, is especially in demand. In this talk, we will first present a generic formalism for N-stage quantum transduction that covers various leading experimental approaches and then identify the generalized matching conditions for achieving maximum conversion efficiency.
We will utilize quantum capacity, the highest achievable qubit communication rate through a channel, to define a single metric that unifies various criteria of a desirable transducer. Using the continuous-time quantum capacities of bosonic pure-loss channels as benchmarks, we investigate the optimal designs of generic quantum transduction schemes implemented by transmitting external signals through a coupled bosonic chain. With physical constraints on the maximal coupling rate, the highest quantum capacity is achieved by transducers with a maximally flat conversion frequency response, analogous to Butterworth electric filters.

Keywords: quantum network, hybrid quantum systems, quantum transduction, quantum capacity