Author: Ueki, H.
Paper Title Page
WEIAA01
 The Frequency Shift and Q of Disordered Superconducting RF Cavities  
 
  • H. Ueki, J.A. Sauls, M. Zarea
    LSU, Baton Rouge, USA
  
  Funding: U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Superconducting Quantum Materials and Systems Center (SQMS) under contract No. DE-AC02-07CH11359.
Su­per­con­duct­ing RF (SRF) cav­ity res­onators with ul­tra­high-Q, orig­i­nally de­vel­oped for par­ti­cle ac­cel­er­a­tor tech­nol­ogy, are a key tech­nol­ogy plat­form for de­tec­tors of rare events, e.g. light by light scat­ter­ing me­di­ated by vir­tual elec­tron-positron pairs, ax­ions [1] and high-fre­quency grav­i­ta­tional waves [2]. The mech­a­nism(s) lead­ing to cur­rent lim­its in Q are not fully un­der­stood. We de­vel­oped a nu­mer­i­cal method to cal­cu­late Q and cav­ity res­o­nant fre­quency shifts based on non­equi­lib­rium the­ory of su­per­con­duc­tiv­ity, in­clud­ing the role of im­pu­rity dis­or­der, com­bined with Slater’s method for solv­ing Maxwell’s equa­tions for the EM field con­fined in a cav­ity [3]. Our re­sults for the fre­quency shift and Q are in ex­cel­lent agree­ment with ex­per­i­men­tal data re­ported by the SRF group at Fer­mi­lab [4]. As a mea­sure of the pre­dic­tive ca­pa­bil­ity of the the­ory we are able to quan­ti­ta­tively ac­count for changes in the res­o­nant fre­quency of order 10 Hz for GHz SRF cav­i­ties over tem­per­a­ture ranges of 0.001 Tc. This level of pre­dic­tive the­ory is es­sen­tial for fur­ther im­prove­ments in per­for­mance of su­per­con­duct­ing res­onators and de­vices for quan­tum sens­ing and quan­tum proces­sors.
[1] Z. Bogorad et al., Phys. Rev. Lett. 123, 021801 (2019).
[2] A. Berlin et al., arXiv:2303.0151.
[3] H. Ueki, M. Zarea, and J. A. Sauls, arXiv:2207.14236.
[4] D. Bafia et al., arXiv:2103.10601. 		 
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