Abstract
Understanding the nature and dynamics of material defects in superconducting circuits is of paramount importance for improving qubit coherence and parameter stability and much needed for implementing large-scale quantum computing. Here we present measurements on individual highly coherent environmental two-level systems (TLS). We trace the spectral diffusion of specific TLS and demonstrate that it originates from the TLS coupling to a small number of low energy incoherent fluctuators. From the analysis of these fluctuations, we access the relevant parameters of low energy fluctuators: dipole moments, switching energies, and, more importantly, interaction energies. Our approach opens up the possibility of deducing the macroscopic observables in amorphous glassy media from direct measurements of local fluctuator dynamics at the microscopic level---a route towards substantiating commonly accepted, but so far phenomenological, models for the decohering environment.
Highlights
All superconducting qubit designs suggested so far suffer from noise and parameter drift and associated decoherence
Where γ ∼ p0/dgate is the coupling strength of the two-level systems (TLS) to the electric field induced by the applied gate voltage, and p0 = qd0 is the TLS dipole moment projected along the direction of the local electric field induced by the gate
We have shown that using frequency tunable superconducting planar resonators in combination with electrostatic gating the spectral diffusion of individual two-level system defects can be mapped and their parameters obtained
Summary
All superconducting qubit designs suggested so far suffer from noise and parameter drift and associated decoherence. Having energy level splittings UTLS > kBT , the near-resonant TLS are not subjected to thermal fluctuations and their parameter instability is attributed to interaction with much more abundant low energy fluctuators with UTLF < kBT. We employ kinetic-inductance frequency tunable planar resonators [25,35] in combination with external electrostatic gating as a versatile platform to resolve individual TLS and to track their dynamics Such a coupled resonator-TLS system becomes a sensitive probe for the study of individual TLF in a wide temperature range from 10 to >300 mK and provides access to TLF-TLF dynamics and interaction energies. We reveal direct evidence of two interacting TLFs, sensed through the same TLS
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
