The extension theory and resonances for a quantum waveguide

H. A. Haus

I. Yu. Popov, S. L. Popova

The resonance effects in a quantum waveguide connected with a resonator is studied in the framework of the zero-width slits model based on the operator extensions theory approach.

Pin-Jia Zhou, Yiwen Wang, Lian-Fu Wei

Since the last decades, superconducting single-photon technology has been extensively used in the quantum security communication and the linear-optic quantum computing fields. Especially, the device based on the coplanar waveguide resonator has attracted substantial interests due to its evident advantages, including the relatively simple structure, the sufficiently high detection efficiency, and the photon-resolving capability, etc. With the profound investigation in optimizing the depositing methods and the material selections, as well as the the development of the relevant theories, the technology of single photon detection based on the coplanar waveguide resonator has obtained a breakthrough. In this review paper we begin from the basic principle of the coplanar waveguide detector, then interpret the relevant theory and some design details of the devices. Finally, based on some of the recent experimental results measured with the low-temperature devices in our lab, we give a brief perspective on the future development of the superconducting coplanar waveguide single photon detectors.

Jingbo Wang

Xiang Guo, Xiaojun Zhang, Mingzhu Weng +5 more

Bound states in the continuum (BICs) have been extensively exploited to enhance light--matter interactions in metamaterials, yet their emergence and utility in multi-atom waveguide platforms remain far less explored. Here we study atom--waveguide-dressed BICs in a one-dimensional coupled-resonator waveguide, where two spatially separated atomic arrays couple to distinct resonators with time-dependent strengths. We show that these BICs support a standing-wave photonic mode and enable the transfer of an arbitrary unknown quantum state between the two arrays with fidelities exceeding $99\%$. The protocol remains robust against both disorder and intrinsic dissipation. Our results establish BICs as long-lived resources for high-fidelity quantum information processing in waveguide-QED architectures.

Yue Cai, Kang‐Jie Ma, Jie Liu +3 more

Abstract Optical quantum routers play a crucial role in quantum networks and have been extensively studied in both theory and experiment, leading to significant advancements in their performance. However, these routers impose stringent requirements for achieving desired routing results, as the incident photon frequency must be in strict resonance with one or several specific frequencies. To address this challenge, we propose an efficient quantum router scheme composed of semi-infinite coupled-resonator waveguide (CRW) and a giant atom. The single-channel router scheme enables stable output with 100% transfer rate over the entire energy band of the CRW. Leveraging this intriguing result, we further propose a multi-channel router scheme that possesses high stability and universality, while also being capable of performing various functionalities. The complete physical explanation of the underlying mechanism for this intriguing result is also presented. We hope that quantum router with output results unaffected by the frequency of the incoming information carriers presents a more reliable solution for the implementation of quantum networks.