  Resonant exchange qubits are a promising addition to the family of
experimentally implemented encodings of single qubits using semiconductor
quantum dots. We have shown previously that it ought to be straightforward to
perform a CPHASE gate between two resonant exchange qubits with a single
exchange pulse. This approach uses energy gaps to suppress leakage rather than
conventional pulse sequences. In this paper we present analysis and simulations
of our proposed two-qubit gate subject to charge and Overhauser field noise at
levels observed in current experiments. Our main result is that we expect
implementations of our two-qubit gate to achieve high fidelities, with errors
at the percent level and gate times comparable to single-qubit operations. As
such, exchange-coupled resonant exchange qubits remain an attractive approach
for quantum computing.
