A hybrid quantum-classical algorithm that finds the minimum eigenvalue of a Hamiltonian. It is the workhorse for near-term quantum chemistry and material science applications and is designed to be NISQ-friendly.
VQE uses a parameterized quantum circuit (the 'ansatz') to prepare a trial quantum state, measures the expectation value of the target Hamiltonian, then a classical optimizer adjusts the circuit parameters to minimize that expectation value. The minimum is the ground-state energy. VQE is hybrid (classical optimization, quantum measurement), tolerant of NISQ-era noise, and applicable to chemistry (molecular ground states), materials science, and certain optimization problems formulated as Hamiltonians.
Computing the H2 molecule's bond dissociation curve using VQE on a 4-qubit quantum simulator, within chemical accuracy of the exact answer.
VQE is the leading candidate for first commercially useful quantum advantage, aimed at quantum chemistry problems that classical methods scale poorly on and that NISQ-era hardware can reach.
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