  Systems which rapidly evolve through symmetry-breaking transitions on
timescales comparable to the fluctuation timescale of the single-particle
excitations may behave very differently than under controlled near-ergodic
conditions. A real-time investigation with high temporal resolution may reveal
new insights into the ordering through the transition that are not available in
static experiments. We present an investigation of the system trajectory
through a normal-to-superconductor transition in a prototype high-temperature
superconducting cuprate in which such a situation occurs. Using a multiple
pulse femtosecond spectroscopy technique we measure the system trajectory and
time-evolution of the single-particle excitations through the transition in
La$_{1.9}$Sr$_{0.1}$CuO$_{4}$ and compare the data to a simulation based on
time-dependent Ginzburg-Landau theory, using laser excitation fluence as an
adjustable parameter controlling the quench conditions in both experiment and
theory. The comparison reveals the presence of significant superconducting
fluctuations which precede the transition on short timescales. By including
superconducting fluctuations as a seed for the growth of superconducting order
we can obtain a satisfactory agreement of the theory with the experiment.
Remarkably, the pseudogap excitations apparently play no role in this process.
