Loss channels affecting lithium niobate phononic crystal resonators at cryogenic temperature

Building a fault-tolerant quantum computer using concatenated cat codes

“…By contrast, the single-phonon loss rate κ 1 involves several dissipation channels, only some of which are directly controllable. Those decay processes that are intrinsic (i.e., not directly controllable) are due to a rich variety of mechanisms such as decay into ensembles of "two-level system" defects or quasi-particles in the superconductors [29], and are difficult to quantify from first principles. Our best reference for these loss rates is experimental data.…”

“…These devices cannot be easily coupled to superconducting circuits, but they offer insight into the decoherence mechanisms affecting nanomechanical resonators and suggest a roadmap for achieving similar levels of coherence with piezoelectric devices. For example, similar studies with lithium niobate PCDRs are already under way [29], and although their coherence times are currently limited to ∼ 1 µs, there is no reason to believe that these numbers could not approach those of the silicon devices after sufficient advances in materials and surface science.…”

“…[28]. We use for its Foster network parameters the values C g = 0.385 fF, C a = 1.682 fF, and L a = 2.614 µH, which in previous work have produced accurate estimates of the linear coupling rate between the phononic mode and other electrical circuits [28,29]. These parameters set ω a /2π ≈ 2.17 GHz as the storage mode frequency, which will remain fixed for the reaminder of this Appendix.…”