Experiment with different noncontextual Hamiltonian structures

UCL-CCS / symmer

An efficient Python-based framework for implementing qubit subspace methods, reducing the resource requirements for near-term quantum simulations.

MIT License

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Experiment with different noncontextual Hamiltonian structures #9

Closed TimWeaving closed 1 year ago

TimWeaving commented 2 years ago

The current CS-VQE implementation prioritises diagonal Hamiltonian terms (hence why the noncontextual energy aligns closely with the Hartree-Fock energy). This is not necessary, for example we might maximise anticommuting contributions - the noncontextual energy will be (considerably) worse in this case, but how does this affect the resulting quantum corrections?

TimWeaving commented 2 years ago

Not strictly addressed in #12 as intended, issue still ongoing.

TimWeaving commented 2 years ago

'diag' and 'legacy' are currently the only supported noncontextual forms in #27.

TimWeaving commented 1 year ago

Added the following in #95:

SingleSweep(_magnitude, _CurrentOrder, _random)
DFS(_magnitude, _largest)
diag

Still need to think about a graph-based implementation (i.e. heuristically solving the disjoint cliques problem).

TimWeaving commented 1 year ago

Largely addressed in #98, in which the StabilizeFirst noncontextual strategy is introduced. This works in reverse to the previous methodology, whereby the stabilizer set is identified upfront and a noncontextual Hamiltonian is built that respects this choice.