  In classical superconductors an energy gap and phase coherence appear
simultaneously with pairing at the transition to the superconducting state. In
high-temperature superconductors, the possibility that pairing and phase
coherence are distinct and independent processes has led to intense
experimental search of their separate manifestations, but so far without
success. Using femtosecond spectroscopy methods we now show that it is possible
to clearly separate fluctuation dynamics of the superconducting pairing
amplitude from the phase relaxation above the critical transition temperature.
Empirically establishing a close correspondence between the superfluid density
measured by THz spectroscopy and superconducting optical pump-probe response
over a wide region of temperature, we find that in differently doped
Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} crystals the pairing gap amplitude
monotonically extends well beyond T_{c}, while the phase coherence shows a
pronounced power-law divergence as T\rightarrow T_{c}, thus showing for the
first time that phase coherence and gap formation are distinct processes which
occur on different timescales.
