Gate decomposition via Householder reflections #758
Conversation
…gging for a single one
…gging for a single one
Update with upstream
There was a problem hiding this comment.
Great contribution! @tanujkhattar can you take a look as well.
My major ask is: can we rename these bloqs and the module to something other than "decompose". We already use that term to mean something else. I see the reference uses the word "synthesis" whose verb would be synthesize
| """Extra soquets inside soqs are: | ||
| * phase_grad: a phase gradient state of size phase_bitsize if internal_phase_gradient | ||
| is set to False | ||
| * refl_ancilla: a clean qubit in |0> if internal_refl_ancilla is set to False | ||
| """ |
There was a problem hiding this comment.
this can probably just be line comments # instead of a docstring. If you want this to be a docstring, it should follow the docstring format.
By "extra soquets" you mean "optional soquets"?
There was a problem hiding this comment.
Not really optional, but required in some situations. For example, if an user sets the internal_phase_grad flag to False then that register has to be provided, but it is not optional in that case.
There was a problem hiding this comment.
optional in a cosmic sense where you can set the flag to true
There was a problem hiding this comment.
@Vicara12 Thanks a lot for opening this PR and apologies for the late review!
I've left a round of comments - Would you still have time to address the comments and get this PR merged? Please let us know one way or the other since this would be a very useful primitive to get in.
Main suggestions are around making changes so we can support symbolic analysis.
| return Signature.build( | ||
| refl_ancilla=(not self.internal_refl_ancilla), | ||
| gate_input=self.gate_bitsize, | ||
| phase_grad=(not self.internal_phase_grad) * self.phase_bitsize, |
There was a problem hiding this comment.
Use QFxp type for the phase gradient register
| def signature(self) -> Signature: | ||
| return Signature.build(target_reg=self.state_bitsize + 1, phase_grad=self.phase_bitsize) | ||
|
|
||
| def build_composite_bloq( |
There was a problem hiding this comment.
Please implement a build_call_graph for symbolic analysis.
Co-authored-by: Tanuj Khattar <[email protected]>
This code implements the first two points in this comment from issue #596 . It adds a bloq that decomposes an arbitrary unitary gate into householder reflections. It allows for partial specification of the gate, in which case the T-gate cost of the bloq is linearly proportional to the number of gates specified.
This code is a necessary part for the goal of implementing a MPS preparation algorithm, even though it is useful on its own for other applications.