Fluid fermionic fragments for optimizing quantum measurements of electronic Hamiltonians in the variational quantum eigensolver

Understand

Measuring the expectation value of the molecular electronic Hamiltonian is one of the challenging parts of the variational quantum eigensolver.

• A widely used strategy is to express the Hamiltonian as a sum of measurable fragments using fermionic operator algebra.
• Such fragments have an advantage of conserving molecular symmetries that can be used for error mitigation.
• The number of measurements required to obtain the Hamiltonian expectation value is proportional to a sum of fragment variances.