  The silicon metal-oxide-semiconductor (MOS) material system is
technologically important for the implementation of electron spin-based quantum
information technologies. Researchers predict the need for an integrated
platform in order to implement useful computation, and decades of advancements
in silicon microelectronics fabrication lends itself to this challenge.
However, fundamental concerns have been raised about the MOS interface (e.g.
trap noise, variations in electron g-factor and practical implementation of
multi-QDs). Furthermore, two-axis control of silicon qubits has, to date,
required the integration of non-ideal components (e.g. microwave strip-lines,
micro-magnets, triple quantum dots, or introduction of donor atoms). In this
paper, we introduce a spin-orbit (SO) driven singlet-triplet (ST) qubit in
silicon, demonstrating all-electrical two-axis control that requires no
additional integrated elements and exhibits charge noise properties equivalent
to other more model, but less commercially mature, semiconductor systems. We
demonstrate the ability to tune an intrinsic spin-orbit interface effect, which
is consistent with Rashba and Dresselhaus contributions that are remarkably
strong for a low spin-orbit material such as silicon. The qubit maintains the
advantages of using isotopically enriched silicon for producing a quiet
magnetic environment, measuring spin dephasing times of 1.6 $\mu$s using 99.95%
$^{28}$Si epitaxy for the qubit, comparable to results from other isotopically
enhanced silicon ST qubit systems. This work, therefore, demonstrates that the
interface inherently provides properties for two-axis control, and the
technologically important MOS interface does not add additional detrimental
qubit noise.
