  In this work we present an experimental demonstration of the Contextual
Subspace Variational Quantum Eigensolver on superconducting quantum hardware.
In particular, we compute the potential energy curve for molecular nitrogen,
where a dominance of static correlation in the dissociation limit proves
challenging for many conventional quantum chemistry techniques. Our quantum
simulations retain good agreement with the full configuration interaction
energy in the chosen STO-3G basis, outperforming all benchmarked
single-reference wavefunction techniques in capturing the bond-breaking
appropriately. Moreover, our methodology is competitive with several
multiconfigurational approaches, but at a considerable saving of quantum
resource, meaning larger active spaces can be treated for a fixed qubit
allowance. To achieve this result we deploy an error mitigation/suppression
strategy comprised of dynamical decoupling, measurement-error mitigation and
zero-noise extrapolation, in addition to circuit parallelization that not only
provides passive averaging of noise but improves the effective shot-yield to
reduce the measurement overhead. Furthermore, we introduce a modification to
previous adaptive ansatz construction algorithms that incorporates
hardware-awareness into our variational circuits to minimize the transpilation
cost for the target qubit topology.
