  We measure for the first time the duration of long-quantum path EUV high
harmonics produced in xenon gas. The long-quantum path contribution to the
high-harmonic signal was carefully controlled by employing a two-colour driving
laser field and a high-harmonic spatial selection in the far field, over a
range of $18-25\,eV$ in photon energy. To characterise the temporal profile of
long quantum path high harmonics, we performed a second order volume
autocorrelation ($2-IVAC$) via two EUV photon double ionization in argon. Our
results show the production and characterisation of a train of EUV pulses from
the long-path with pulse duration as short as $1.4\,fs$. This measurement
demonstrates that the long-quantum path emission can have enough flux for
performing non-linear EUV experiments, and that the long trajectories enable a
pulse duration short enough to support measurements with a temporal resolution
below $2\,fs$.
