A Feasible Approach for Automatically Differentiable Unitary Coupled-Cluster on Quantum Computers

Abstract

We develop computationally affordable and encoding independent gradient evaluation procedures for unitary coupled-cluster type operators, applicable on quantum computers. We show that, within our framework, the gradient of an expectation value with respect to a parameterized n-fold fermionic excitation can be evaluated by four expectation values of similar form and size, whereas most standard approaches based on the direct application of the parameter-shift-rule come with an associated cost of O(2^(2n)) expectation values. For real wavefunctions, this cost can be further reduced to two expectation values. Our strategies are implemented within the open-source package tequila and allow blackboard style construction of differentiable objective functions. We illustrate initial applications for electronic ground and excited states.

References in corpus (3)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Simulated Quantum Computation of Molecular Energies
• Exact Parameterization of Fermionic Wave Functions via Unitary Coupled Cluster Theory

Cited by in corpus (1)

• Tequila: A platform for rapid development of quantum algorithms