High-Energy Quasiparticle Injection in Mesoscopic Superconductors

At nonzero temperatures, superconductors contain excitations known as Bogoliubov quasiparticles. The mesoscopic dynamics of quasiparticles are crucial to designing quantum information processors, among other devices. Knowledge of these dynamics stems from experiments in which quasiparticles are injected in a controlled fashion, typically at energies comparable to the superconducting energy gap. Here we perform tunnel spectroscopy of a mesoscopic superconductor under high electric field. We observe quasiparticle injection into titanium with 10^6 times the gap energy, an unexplored regime of quasiparticle dynamics. We expect that high-energy injection will be useful for developing quasiparticle-tolerant quantum information processors, will allow rapid control of resonator quality factors, and will enable the design of electric-field-controlled superconducting devices with new functionality.