Add a phased classical action for SelectedMajoranaFermion #1778
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Merge with upstream.
mpharrigan
reviewed
Jan 6, 2026
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| if len(self.control_registers) > 1 or len(self.selection_registers) > 1: | ||
| return NotImplemented |
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is this restriction necessary?
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I'm not sure - it is hard for me to understand what this gate does in the general case. Is my understanding in #1699 (comment) correct?
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| if self.target_gate != cirq.X: | ||
| return NotImplemented |
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In combination with basis_state_phase, this should be able to support Z as well. Z imparts a phase (and leaves the computational basis states unaffected)
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I have now added Z.
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| max_selection = self.selection_registers[0].dtype.iteration_length_or_zero() - 1 | ||
| target = (2 ** (max_selection - selection)) ^ target |
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can you add a comment describing how this logic works
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Add a phased classical action for SelectedMajoranaFermion.
The classical action only exists for some choices of
target_gate, and we assume specificallytarget_gate=cirq.X(and also that there is only 1 control register and 1 selection register).Fixes #1699