  Quantum computing has emerged as a promising platform for simulating strongly
correlated systems in chemistry, for which the standard quantum chemistry
methods are either qualitatively inaccurate or too expensive. However, due to
the hardware limitations of the available noisy near-term quantum devices,
their application is currently limited only to small chemical systems. One way
for extending the range of applicability can be achieved within the quantum
embedding approach. Herein, we employ the projection-based embedding method for
combining the variational quantum eigensolver (VQE) algorithm, although not
limited to, with density functional theory (DFT). The developed VQE-in-DFT
method is then implemented efficiently on a real quantum device and employed
for simulating the triple bond breaking process in butyronitrile. The results
presented herein show that the developed method is a promising approach for
simulating systems with a strongly correlated fragment on a quantum computer.
The developments as well as the accompanying implementation will benefit many
different chemical areas including the computer aided drug design as well as
the study of metalloenzymes with a strongly correlated fragment.
