  Interference of multiple photons via a linear-optical network has profound
applications for quantum foundation, quantum metrology and quantum computation.
Particularly, a boson sampling experiment with a moderate number of photons
becomes intractable even for the most powerful classical computers, and will
lead to "quantum supremacy". Scaling up from small-scale experiments requires
highly indistinguishable single photons, which may be prohibited for many
physical systems. Here we experimentally demonstrate a time-resolved version of
boson sampling by using photons not overlapping in their frequency spectra from
three atomic-ensemble quantum memories. Time-resolved measurement enables us to
observe nonclassical multiphoton correlation landscapes. An average fidelity
over several interferometer configurations is measured to be 0.936(13), which
is mainly limited by high-order events. Symmetries in the landscapes are
identified to reflect symmetries of the optical network. Our work thus provides
a route towards quantum supremacy with distinguishable photons.
