  We introduce a simple, widely applicable formalism for designing
"error-divisible" two qubit gates: a quantum gate set where fractional
rotations have proportionally reduced error compared to the full entangling
gate. In current noisy intermediate-scale quantum (NISQ) algorithms,
performance is largely constrained by error proliferation at high circuit
depths, of which two-qubit gate error is generally the dominant contribution.
Further, in many hardware implementations, arbitrary two qubit rotations must
be composed from multiple two-qubit stock gates, further increasing error. This
work introduces a set of criteria, and example waveforms and protocols to
satisfy them, using superconducting qubits with tunable couplers for
constructing continuous gate sets with significantly reduced error for
small-angle rotations. If implemented at scale, NISQ algorithm performance
would be significantly improved by our error-divisible gate protocols.
