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Direct measurement of microwave loss in Nb films for superconducting qubits

Journal Article · · Appl.Phys.Lett.
DOI:https://doi.org/10.1063/5.0226611· OSTI ID:2407094
 [1];  [2];  [2];  [2];  [3];  [2];  [2];  [4];  [4];  [4];  [2];  [2]
  1. Fermilab; Jefferson Lab; Old Dominion U.
  2. Fermilab
  3. Jefferson Lab; Old Dominion U.
  4. CERN
+ Show Author Affiliations
Niobium films are a key component in modern two-dimensional superconducting qubits, yet their contribution to the total qubit decay rate is not fully understood. The presence of different layers of materials and interfaces makes it difficult to identify the dominant loss channels in present two-dimensional qubit designs. In this paper, we present the study that directly correlates measurements of RF losses in such films to material parameters by investigating a high-power impulse magnetron sputtered (HiPIMS) film atop a three-dimensional niobium superconducting radio frequency (SRF) resonator. By using a 3D SRF structure, we are able to isolate the niobium film loss from other contributions. Our findings indicate that microwave dissipation in the HiPIMS-prepared niobium films, within the quantum regime, resembles that of record-high intrinsic quality factor of bulk niobium SRF cavities, with lifetimes extending into seconds. Microstructure and impurity level of the niobium film do not significantly affect the losses. These results set the scale of microwave losses in niobium films and show that niobium losses do not dominate the observed coherence times in present two-dimensional superconducting qubit designs, instead highlighting the dominant role of the dielectric oxide in limiting the performance. We can also set a bound for when niobium film losses will become a limitation for qubit lifetimes.
Research Organization:
CERN; Old Dominion U.; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Organization:
US Department of Energy
DOE Contract Number:
AC02-07CH11359; 89243024CSC000002
OSTI ID:
2407094
Report Number(s):
FERMILAB-PUB-24-0374-SQMS; oai:inspirehep.net:2807385; arXiv:2407.08856
Journal Information:
Appl.Phys.Lett., Journal Name: Appl.Phys.Lett. Journal Issue: 12 Vol. 125
Country of Publication:
United States
Language:
English

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