Bolometer operating at the threshold for circuit quantum electrodynamics

R. Kokkoniemi, J.-P. Girard, Dibyendu Hazra, A. Laitinen, Joonas Govenius, R.E. Lake, I. Sallinen, Visa Vesterinen, M. Partanen, J. Y. Tan, K. W. Chan, K. Y. Tan, P. Pakonen, Mikko Möttönen (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

67 Citations (Scopus)


Radiation sensors based on the heating effect of absorbed radiation are typically simple to operate and flexible in terms of input frequency, so they are widely used in gas detection, security, terahertz imaging, astrophysical observations and medical applications. Several important applications are currently emerging from quantum technology and especially from electrical circuits that behave quantum mechanically, that is, circuit quantum electrodynamics. This field has given rise to single-photon microwave detectors and a quantum computer that is superior to classical supercomputers for certain tasks. Thermal sensors hold potential for enhancing such devices because they do not add quantum noise and they are smaller, simpler and consume about six orders of magnitude less power than the frequently used travelling-wave parametric amplifiers. However, despite great progress in the speed and noise levels of thermal sensors, no bolometer has previously met the threshold for circuit quantum electrodynamics, which lies at a time constant of a few hundred nanoseconds and a simultaneous energy resolution of the order of 10h gigahertz (where h is the Planck constant). Here we experimentally demonstrate a bolometer that operates at this threshold, with a noise-equivalent power of 30 zeptowatts per square-root hertz, comparable to the lowest value reported so far, at a thermal time constant two orders of magnitude shorter, at 500 nanoseconds. Both of these values are measured directly on the same device, giving an accurate estimation of 30h gigahertz for the calorimetric energy resolution. These improvements stem from the use of a graphene monolayer with extremely low specific heat as the active material. The minimum observed time constant of 200 nanoseconds is well below the dephasing times of roughly 100 microseconds reported for superconducting qubits and matches the timescales of currently used readout schemes, thus enabling circuit quantum electrodynamics applications for bolometers.

Original languageEnglish
Pages (from-to)47–51
Issue number7827
Publication statusPublished - 30 Sept 2020
MoE publication typeA1 Journal article-refereed


We acknowledge the provision of facilities and technical support by Aalto University at OtaNano – Micronova Nanofabrication Center and LTL Infrastructure, which is part of the European Microkelvin Platform (EMP, number 824109 EU Horizon 2020). We have received funding from the European Research Council under Consolidator Grant number 681311 (QUESS) and under Advanced Grant number 670743 (QuDeT), the European Commission through the H2020 programme project QMiCS (grant agreement 820505, Quantum Flagship), the Academy of Finland through its Centres of Excellence Programme (project numbers 312300, 312059 and 312295) and grants (numbers 314447, 314448, 314449, 305237, 316551, 308161, 335460, and 314302), the Finnish Cultural Foundation and the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters.


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