  Efficient generation of single photons is one of the key challenges of
building photonic quantum technology, such as quantum computers and
long-distance quantum networks. Photon source multiplexing -- where successful
pair generation is heralded by the detection of one of the photons, and its
partner is routed to a single mode output -- has long been known to offer a
concrete solution, with output probability tending toward unity as loss is
reduced. Here, we present a temporally multiplexed integrated single photon
source based on a silicon waveguide and a low-loss fibre switch and loop
architecture, which achieves enhancement of the single photon output
probability of $4.5 \pm 0.5$, while retaining $g^{(2)}(0) = 0.01$.
