Nearly quantum-limited microwave amplification via interfering degenerate stimulated emission in a single artificial atom
Journal article, 2025
Reaching the quantum limit for added noise in amplification processes is an important step toward many quantum technologies. Nearly quantum-limited traveling-wave parametric amplifiers with Josephson junction arrays have been developed and recently even become commercially available. However, the fundamental question of whether a single atom also can reach this quantum limit has not yet been answered in practice. Here, we investigate the amplification of a microwave probe signal by a superconducting artificial atom, a transmon, at the end of a semi-infinite transmission line, under a strong pump field. The end of the transmission line acts as a mirror for microwave fields. Due to the weak anharmonicity of the artificial atom, the strong pump field creates multi-photon excitations among the dressed states. Transitions between these dressed states, Rabi sidebands, give rise to either amplification or attenuation of the weak probe. We obtain a maximum power amplification of 1.402 +/- 0.025, higher than in any previous experiment with a single artificial atom. We achieve near-quantum-limited added noise (0.157 +/- 0.003 quanta; the quantum limit is 0.143 +/- 0.006 quanta for this level of amplification), due to quantum coherence between Rabi sidebands, leading to constructive interference between emitted photons.
Author
Fahad Aziz
National Tsing Hua University
City University of Hong Kong
Kuan-Ting Lin
National Taiwan University
Hon Hai Research Institute
Ping-Yi Wen
National Chung Cheng University
Yu-Chen Lin
National Taiwan University
Emely Wiegand
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Ching-Ping Lee
National Tsing Hua University
Yu-Ting Cheng
National Tsing Hua University
Yong Lu
Xidian University
Ching-Yeh Chen
National Tsing Hua University
Chin-Hsun Chien
National Tsing Hua University
Kai-Min Hsieh
National Tsing Hua University
Yu-Huan Huang
National Tsing Hua University
Haw-Tyng Huang
National Taiwan University
Hou Ian
University of Macau
Jeng-Chung Chen
National Tsing Hua University
Yen-Hsiang Lin
National Tsing Hua University
Anton Frisk Kockum
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Guin-Dar Lin
National Taiwan University
Hon Hai Research Institute
Natl Ctr Theoret Sci
Io-Chun Hoi
City University of Hong Kong
npj Quantum Information
20566387 (eISSN)
Vol. 11 1 45Giant atoms - a new regime in quantum optics
Swedish Research Council (VR) (2019-03696), 2020-01-01 -- 2023-12-31.
Open Superconducting Quantum Computers (OpenSuperQPlus)
European Commission (EC) (EC/HE/101113946), 2023-03-01 -- 2026-08-31.
Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Condensed Matter Physics
DOI
10.1038/s41534-025-00993-3