Error rate reduction of single-qubit gates via noise-aware decomposition
  into native gates
In the current era of Noisy Intermediate-Scale Quantum (NISQ) technology, the
practical use of quantum computers remains inhibited by our inability to aptly
decouple qubits from their environment to mitigate computational errors. In
this work, we introduce an approach by which knowledge of a qubit's initial
quantum state and the standard parameters describing its decoherence can be
leveraged to mitigate the noise present during the execution of a single-qubit
gate. We benchmark our protocol using cloud-based access to IBM quantum
processors. On ibmq_rome, we demonstrate a reduction of the single-qubit error
rate by $38\%$, from $1.6 \times 10 ^{-3}$ to $1.0 \times 10 ^{-3}$, provided
the initial state of the input qubit is known. On ibmq_bogota, we prove that
our protocol will never decrease gate fidelity, provided the system's $T_1$ and
$T_2$ times have not drifted above $100$ times their assumed values. The
protocol can be used to reduce quantum state preparation errors, as well as to
improve the fidelity of quantum circuits for which some knowledge of the
qubits' intermediate states can be inferred. This work presents a pathway to
using information about noise levels and quantum state distributions to
significantly reduce error rates associated with quantum gates via optimized
decomposition into native gates.
Thomas J. Maldonado Johannes Flick Stefan Krastanov Alexey Galda