  Electrons in two-dimensional hexagonal materials have valley degree of
freedom, which can be used to encode and process quantum information. The
valley-selective excitations, governed by the circularly polarised light
resonant with the material's band-gap, continues to be the foundation of
valleytronics. It is often assumed that achieving valley selective excitation
in pristine graphene with all-optical means is not possible due to the
inversion symmetry of the system. Here we demonstrate that both
valley-selective excitation and valley-selective high-harmonic generation can
be achieved in pristine graphene by using the combination of two
counter-rotating circularly polarized fields, the fundamental and its second
harmonic. Controlling the relative phase between the two colours allows us to
select the valleys where the electron-hole pairs and higher-order harmonics are
generated. We also describe an all-optical method for measuring valley
polarization in graphene with a weak probe pulse. This work offers a robust
recipe to write and read valley-selective electron excitations in materials
with zero bandgap and zero Berry curvature.
