Calculation control for hybrid computing of Hamiltonian eigensolutions

A classical computing system, including:

• at least one processor;
• and
• at least one memory that includes instructions, which when executed by the at least one processor, configure the at least one processor to:
• select K basis states from an ansatz space of a chemical system to define a core space for the chemical system, wherein:
• the ansatz space consists of a subset of basis states from a whole basis space of the chemical system that are sample-able from a single parameterized quantum circuit on a quantum computer system,
• the whole basis space consists of every basis state to describe the chemical system,
• the K basis states are selected according to a selection protocol to define the core space for the chemical system, wherein the selection protocol identifies a plurality of individual basis states from the ansatz space to include in the core space using at least one selection criterion other than a fixed-K-greatest selection protocol in which a given individual basis state of the plurality of individual basis states would be selected to be among the K basis states based on a magnitude of a probability of the given individual basis state being among the K-highest probabilities in the ansatz space:
• compute, via at least one eigensolver, an eigensolution for the chemical system from the core space;
• and
• output the eigensolution for the chemical system.

A hybrid computing system, comprising:

• at least one quantum computing system, including at least one eigensolver;
• and
• at least one classical computing system, including:
• at least one processor;
• and
• at least one memory that includes instructions, which when executed by the at least one processor, configure the at least one processor to:
• select K basis states from an ansatz space of a chemical system to define a core space for the chemical system, wherein:
• the ansatz space consists of a subset of basis states from a whole basis space of the chemical system that are sample-able from a single parameterized quantum circuit on the at least one quantum computer system,
• the whole basis space consists of every basis state to describe the chemical system,
• the K basis states are selected according to a selection protocol to define the core space for the chemical system, wherein the selection protocol identifies a plurality of individual basis states from the ansatz space to include in the core space using at least one selection criterion other than a fixed-K-greatest selection protocol in which a given individual basis state of the plurality of individual basis states would be selected to be among the K basis states based on a magnitude of a probability of the given individual basis state being among the K-highest probabilities in the ansatz space,
• wherein the at least one eigensolver:
• computes an eigensolution for the chemical system from the core space;
• and
• outputs the eigensolution for the chemical system.

A method, comprising:

• selecting K basis states from an ansatz space of a chemical system to define a core space for the chemical system, wherein:
• the ansatz space consists of a subset of basis states from a whole basis space of the chemical system that are sample-able from a single parameterized quantum circuit on a quantum computer system,
• the whole basis space consists of every basis state to describe the chemical system,
• the K basis states are selected according to a selection protocol to define the core space for the chemical system, wherein the selection protocol identifies a plurality of individual basis states from the ansatz space to include in the core space using at least one selection criterion, wherein the selection protocol is chosen from a group consisting of:
• an electron preserving selection protocol;
• an alpha beta electron preserving selection protocol;
• an overlap partition selection protocol with partition bias;
• an overlap partition selection protocol with breadth-first bias;
• an overlap partition selection protocol with best-first bias;
• and
• an iterative contribution-based selection protocol;
• computing, via an eigensolver, an eigensolution for the chemical system from the core space;
• and
• outputting the eigensolution for the chemical system.