[open-systems] Phased classical simulation #1590
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This pull request is the second in a series for supporting open system (classical data & measurement), roadmap item quantumlib#445. ~~This branch is based on quantumlib#1584~~ ## `Bloq.basis_state_phase` This new method can be overridden for phased-classical gates. In this PR, I show how `CZ` can support this new method. This leaves the basis states alone but applies a phase when `11` is encountered. ## `PhasedClassicalSimState(ClassicalSimState)` I refactored the classical simulator into a (mutable) class with initialization `.from_cbloq(...)`, binst-by-binst stepping `.step()`, and finalization `.finalize()`. These can be combined with `.simulate()`, which is the new backend for the familiar entry points `Bloq.call_classically(...)` and friends. Doing ordinary classical simulation will raise an error if it encounters a bloq with a non-trivial phase. The phased classical simulator will raise an error if it encounters a bloq without classical action; otherwise it will propagate phase. If a bloq does not specifically annotate a phase (but does indeed have classical action), the trivial +1 phase is assumed. ## Non-changes (yet) This PR does not directly support any "open systems" things. The ultimate goal is to support fuzz-testing measurement-based uncomputation. Since MBUC involves tracking phases, this PR is a necessary but not sufficient pre-requisite. ## Related - This PR unblocks quantumlib#1527 - quantumlib#1499 easier to test - https://arxiv.org/abs/2105.13410 has a ton of cool circuit constructions that can be tested with this
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This pull request is the second in a series for supporting open system (classical data & measurement), roadmap item #445.
This branch is based on #1584Bloq.basis_state_phaseThis new method can be overridden for phased-classical gates. In this PR, I show how
CZcan support this new method. This leaves the basis states alone but applies a phase when11is encountered.PhasedClassicalSimState(ClassicalSimState)I refactored the classical simulator into a (mutable) class with initialization
.from_cbloq(...), binst-by-binst stepping.step(), and finalization.finalize(). These can be combined with.simulate(), which is the new backend for the familiar entry pointsBloq.call_classically(...)and friends.Doing ordinary classical simulation will raise an error if it encounters a bloq with a non-trivial phase. The phased classical simulator will raise an error if it encounters a bloq without classical action; otherwise it will propagate phase. If a bloq does not specifically annotate a phase (but does indeed have classical action), the trivial +1 phase is assumed.
Non-changes (yet)
This PR does not directly support any "open systems" things. The ultimate goal is to support fuzz-testing measurement-based uncomputation. Since MBUC involves tracking phases, this PR is a necessary but not sufficient pre-requisite.
Related
on_classical_valsforCSwapApprox? #1527