  Nonequilibrium quasiparticles are ubiquitous in superconducting electronics.
These quasiparticles can trap in the internal Andreev bound states of a
phase-biased Josephson junction, providing a mechanism for studying their
presence and behavior. We characterize a quasiparticle trapping detector device
based on a two-junction aluminum nanobridge superconducting quantum
interference device incorporated into a transmission-line resonator. When
flux-biased, distinct resonant frequencies develop depending on the trapped
quasiparticle number. We demonstrate continuous detection of up to 3 trapped
quasiparticles, with detection of a trapped quasiparticle with signal-to-noise
ratio of 27 in 5 $\mu$s. We describe initial measurements of quasiparticle
behavior and discuss the possible optimization and application of such detector
devices.
