  The accretion of material onto young protostars is accompanied by the
launching of outflows. Observations show that accretion, and therefore also
outflows, are episodic. However, the effects of episodic outflow feedback on
the core-scale are not well understood. We have performed 88 Smoothed Particle
Hydrodynamic simulations of turbulent dense $1 \, \mathrm{M}_{\odot}$ cores, to
study the influence of episodic outflow feedback on the stellar multiplicity
and the star formation efficiency (SFE). Protostars are represented by sink
particles, which use a sub-grid model to capture stellar evolution, inner-disc
evolution, episodic accretion and the launching of outflows. By comparing
simulations with and without episodic outflow feedback, we show that
simulations with outflow feedback reproduce the binary statistics of young
stellar populations, including the relative proportions of singles, binaries,
triples, etc. and the high incidence of twin binaries with $q\geq 0.95$;
simulations without outflow feedback do not. Entrainment factors (the ratio
between total outflowing mass and initially ejected mass) are typically $\sim
7\pm 2$, but can be much higher if the total mass of stars formed in a core is
low and/or outflow episodes are infrequent. By decreasing both the mean mass of
the stars formed and the number of stars formed, outflow feedback reduces the
SFE by about a factor of 2 (as compared with simulations that do not include
outflow feedback).
