Fix kraus channels for fallbacks to super-operators #7537
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- There were a few issues with the new strategy to fall back to super-operator calculations using apply_channels. - First, the super_operator_to_kraus function is generally not precise or numerically stable enough to support an atol of 1e-10 so loosened this to 1e-6 and also allowed the ability to specify this as a parameter. - Next, some operators define decomposition, so cirq.kraus should try to decompose and get a unitary before falling back to using apply_channel.
mhucka
requested changes
Jul 25, 2025
| @@ -149,6 +153,8 @@ def kraus( | |||
| default: Determines the fallback behavior when `val` doesn't have | |||
| a channel. If `default` is not set, a TypeError is raised. If | |||
| default is set to a value, that value is returned. | |||
| atol: If calculating kraus channels from channels, use this tolerance | |||
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| def test_kraus_channel_with_has_unitary(): | ||
| """CZSWAP is a gate with no unitary but has a unitary.""" |
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I think there is something wrong with this docstring ;-)
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #7537 +/- ##
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- Coverage 97.53% 97.53% -0.01%
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Files 1095 1095
Lines 99006 99014 +8
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+ Hits 96570 96576 +6
- Misses 2436 2438 +2 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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This was referenced Aug 5, 2025
pavoljuhas
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Aug 14, 2025
- There were a few issues with the new strategy to fall back to super-operator calculations using apply_channels. - First, the super_operator_to_kraus function is generally not precise or numerically stable enough to support an atol of 1e-10 so loosened this to 1e-6 and also allowed the ability to specify this as a parameter. - Next, some operators define decomposition, so cirq.kraus should try to decompose and get a unitary before falling back to using apply_channel. Fixes: #7536
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Fixes: #7536