  Entanglement, describing the inseparability of a quantum multiparty system,
is one of the most intriguing features of quantum mechanics. Violation of Bell
inequality, for ruling out the possibility of local hidden variable theories,
is commonly used as a strong witness for quantum entanglement. In previous Bell
test experiments with photonic entanglement based on two-photon coincidence
measurement, the photon temporal wave packets are absorbed completely by the
detectors. That is, the photon coherence time is much shorter than the
detection time window. Here we demonstrate generation of frequency-bin
entangled narrowband biphotons, and for the first time, test the
Clauser-Horne-Shimony-Holt (CHSH) Bell inequality |S|<= 2 for their nonlocal
temporal correlations with time-resolved detection. We obtain a maximum |S|
value of 2.52+/-0.48 that violates the CHSH inequality. Our result will have
applications in quantum information processing involving time-frequency
entanglement.
