  In this letter, it is proposed that cryogenic quantum bits can operate based
on the nonlinearity due to the quantum capacitance of two-dimensional Dirac
materials, and in particular graphene. The anharmonicity of a typical
superconducting quantum bit is calculated, and the sensitivity of quantum bit
frequency and anharmonicity with respect to temperature are found. Reasonable
estimates reveal that a careful fabrication process can reveal expected
properties, putting the context of quantum computing hardware into new
perspectives.
