Experimental realization of on-chip few-photon control around exceptional points

• Published in: Nature communications Vol. 15; no. 1; pp. 9848 - 7
• Main Authors: Song, Pengtao, Ruan, Xinhui, Ding, Haijin, Li, Shengyong, Chen, Ming, Huang, Ran, Kuang, Le-Man, Zhao, Qianchuan, Tsai, Jaw-Shen, Jing, Hui, Yang, Lan, Nori, Franco, Zheng, Dongning, Liu, Yu-xi, Zhang, Jing, Peng, Zhihui
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 14-11-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/400/482; 639/925/927/1064; 639/925/927/481; Broken symmetry; Eigenvalues; Eigenvectors; Humanities and Social Sciences; Microwave transmission; multidisciplinary; Phase transitions; Photons; Science; Science (multidisciplinary); Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-54199-w

Non-Hermitian physical systems have attracted considerable attention in recent years for their unique properties around exceptional points (EPs), where the eigenvalues and eigenstates of the system coalesce. Phase transitions near exceptional points can lead to various interesting phenomena, such as unidirectional wave transmission. However, most of those studies are in the classical regime and whether these properties can be maintained in the quantum regime is still a subject of ongoing studies. Using a non-Hermitian on-chip superconducting quantum circuit, here we observe a phase transition and the corresponding exceptional point between the two phases. Furthermore, we demonstrate that unidirectional microwave transmission can be achieved even in the few-photon regime within the broken symmetry phase. This result holds some potential applications, such as on-chip few-photon microwave isolators. Our study reveals the possibility of exploring the fundamental physics and practical quantum devices with non-Hermitian systems based on superconducting quantum circuits.
The authors observe an exceptional point and the corresponding phase transition in a superconducting non-Hermitian circuit. They find non-reciprocal microwave transmission can be achieved within the broken symmetry phase in the few-photon regime.