  The ability of quantum computers to overcome the exponential memory scaling
of many-body problems is expected to transform quantum chemistry. Quantum
algorithms require accurate representations of electronic states on a quantum
device, but current approximations struggle to combine chemical accuracy and
gate-efficiency while preserving physical symmetries, and rely on
measurement-intensive adaptive methods that tailor the wave function ansatz to
each molecule. In this contribution, we present a symmetry-preserving and
gate-efficient ansatz that provides chemically accurate molecular energies with
a well-defined circuit structure. Our approach exploits local qubit
connectivity, orbital optimisation, and connections with generalised valence
bond theory to maximise the accuracy that is obtained with shallow quantum
circuits. Numerical simulations for molecules with weak and strong electron
correlation, including benzene, water, and the singlet-triplet gap in
tetramethyleneethane, demonstrate that chemically accurate energies are
achieved with as much as 84% fewer two-qubit gates compared to state-of-the-art
adaptive ansatz techniques.
