  Many quantum algorithms rely on a quality initial state for optimal
performance. Preparing an initial state for specific applications can
considerably reduce the cost of probabilistic algorithms such as the well
studied quantum phase estimation (QPE). Fortunately, in the application space
of quantum chemistry, generating approximate wave functions for molecular
systems is well studied, and quantum computing algorithms stand to benefit from
importing these classical methods directly into a quantum circuit. In this
work, we propose a state preparation method based on coupled cluster (CC)
theory, which is a pillar of quantum chemistry on classical computers, by
incorporating mid-circuit measurements into the circuit construction.
Currently, the most well studied state preparation method for quantum chemistry
on quantum computers is the variational quantum eigensolver (VQE) with a
unitary-CC with single- and double-electron excitation terms (UCCSD) ansatz
whose operations are limited to unitary gates. We verify the accuracy of our
state preparation protocol using mid-circuit measurements by performing energy
evaluation and state overlap computation for a set of small chemical systems.
We further demonstrate that our approach leads to a reduction of the classical
computation overhead, and the number of CNOT and T gates by 28% and 57% on
average when compared against the standard VQE-UCCSD protocol.
