Satrya Christoforus Dimas, Chang Yu-Cheng, Strelnikov Aleksandr S, Upadhyay Rishabh, Mäkinen Ilari K, Peltonen Joonas T, Karimi Bayan, Pekola Jukka P
Department of Applied Physics, Pico group, QTF Centre of Excellence, Aalto University, Aalto, Finland.
VTT Technical Research Centre of Finland Ltd, Espoo, Finland.
Nat Commun. 2025 May 13;16(1):4435. doi: 10.1038/s41467-025-58919-8.
Superconducting circuits provide a versatile and controllable platform for studies of fundamental quantum phenomena as well as for quantum technology applications. A conventional technique to read out the state of a quantum circuit or to characterize its properties is based on RF measurement schemes. Here we demonstrate a simple DC measurement of a thermal spectrometer to investigate properties of a superconducting circuit, in this proof-of-concept experiment a coplanar waveguide resonator. A fraction of the microwave photons in the resonator is absorbed by an on-chip bolometer, resulting in a measurable temperature rise. By monitoring the DC signal of the thermometer due to this process, we are able to determine the resonance frequency and the lineshape (quality factor) of the resonator. The demonstrated scheme, which is a simple DC measurement, offers a wide frequency band potentially reaching up to 200 GHz, far exceeding that of the typical RF spectrometer. Moreover, the thermal measurement yields a highly frequency independent reference level of the Lorentzian absorption signal. In the low power regime, the measurement is fully calibration-free. Our technique offers an alternative spectrometer for quantum circuits.
超导电路为研究基本量子现象以及量子技术应用提供了一个通用且可控的平台。一种读出量子电路状态或表征其特性的传统技术基于射频测量方案。在此，我们展示了一种用于研究超导电路特性的热谱仪的简单直流测量方法，在这个概念验证实验中使用的是共面波导谐振器。谐振器中的一部分微波光子被片上测辐射热计吸收，导致可测量的温度升高。通过监测由于这个过程产生的温度计的直流信号，我们能够确定谐振器的共振频率和线形（品质因数）。所展示的方案是一种简单的直流测量方法，提供了一个潜在可达200 GHz的宽频带，远远超过典型射频谱仪的频带。此外，热测量产生了一个高度与频率无关的洛伦兹吸收信号参考电平。在低功率状态下，测量完全无需校准。我们的技术为量子电路提供了一种替代谱仪。
