  Graphene quantum dots are promising candidates for qubits due to weak
spin-orbit and hyperfine interactions. The hyperfine interaction, controllable
via isotopic purification, could be the key to further improving the coherence.
Here, we use isotopically enriched graphite crystals of both $^{12}$C and
$^{13}$C grown by high-pressure-high-temperature method to exfoliate graphene
layers. We fabricated Hall bar devices and performed quantum transport
measurements, revealing mobilities exceeding $10^{5}$$\textrm{cm}^{2}/Vs$ and a
long mean free path of microns, which are as high as natural graphene.
Shubnikov-de Haas oscillations, quantum Hall effect up to the filling factor of
one, and Brown-Zak oscillations due to the alignment of hBN and graphene are
observed thanks to the high mobility. These results constitute a material
platform for physics and engineering of isotopically-enriched graphene qubits.
