From 184500d6ece40fea04e1965d07f72d2fb08d4a4a Mon Sep 17 00:00:00 2001 From: Dave Bacon Date: Tue, 29 Mar 2022 11:44:50 -0700 Subject: [PATCH] Clarify virtual tag docstring (#5161) Propose that instead of changing whether virtual tags are applied to noise models, we instead just clarify what it means to be virtual. Fixes: #2984 --- cirq-core/cirq/ops/tags.py | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/cirq-core/cirq/ops/tags.py b/cirq-core/cirq/ops/tags.py index f51d2962b51..acb30fe2788 100644 --- a/cirq-core/cirq/ops/tags.py +++ b/cirq-core/cirq/ops/tags.py @@ -18,6 +18,12 @@ class VirtualTag: """A TaggedOperation tag indicating that the operation is virtual. + Virtual operations are one that do not correspond to some physical signal sent + to the quantum computer. An example of such an operation is a Z rotation gates + where the gate is not enacted in the circuit, but instead is tracked in software. + Another example is noise that has been added to a gate to make it appear as + a noisy gate in a `cirq.NoiseModel`. + Operations marked with this tag are presumed to have zero duration of their own, although they may have a non-zero duration if run in the same Moment as a non-virtual operation.