  We experimentally study the generation of photon pairs via spontaneous
four-wave mixing with two distinct laser pulses. We find that the dual-pump
technique enables new capabilities: 1) a new characterization methodology to
measure noise contributions, source brightness and photon collection
efficiencies directly from raw photon-count measurements; 2) an enhanced
ability to generate heralded single photons in a pure quantum state; and 3) the
ability to derive upper and lower bounds on heralded-photon quantum state
purity from measurements of photon-number statistics even in the presence of
noise. Such features are highly valuable in photon-pair sources for quantum
applications.
