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Fix num_qubits property on AsymetricDepolarizing Channel #4652

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merged 4 commits into from
Nov 10, 2021
Merged

Fix num_qubits property on AsymetricDepolarizing Channel #4652

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e479d18
Fix num_qubits property on Assymetric Depolarizing Channel
dabacon Nov 9, 2021
b0f88dc
Make more explicit
dabacon Nov 9, 2021
690d4f6
Fix changes
dabacon Nov 10, 2021
18377c6
Merge branch 'master' into propertyhell
dabacon Nov 10, 2021
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12 changes: 6 additions & 6 deletions cirq-core/cirq/ops/common_channels.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
from cirq import protocols, value
from cirq.ops import raw_types, common_gates, pauli_gates, gate_features, identity


if TYPE_CHECKING:
import cirq

Expand Down Expand Up @@ -53,6 +54,10 @@ def __init__(
(including identity). The input $\rho$ is the density matrix before the
depolarization.

Note: prior to Cirq v0.14, this class contained `num_qubits` as a property.
This violates the contract of `cirq.Gate` so it was removed. One can
instead get the number of qubits by calling the method `num_qubits`.

Args:
p_x: The probability that a Pauli X and no other gate occurs.
p_y: The probability that a Pauli Y and no other gate occurs.
Expand Down Expand Up @@ -178,11 +183,6 @@ def p_z(self) -> float:
raise ValueError('num_qubits should be 1')
return self._error_probabilities.get('Z', 0.0)

@property
def num_qubits(self) -> int:
"""The number of qubits"""
return self._num_qubits

@property
def error_probabilities(self) -> Dict[str, float]:
"""A dictionary from Pauli gates to probability"""
Expand All @@ -193,7 +193,7 @@ def _json_dict_(self) -> Dict[str, Any]:

def _approx_eq_(self, other: Any, atol: float) -> bool:
return (
self.num_qubits == other.num_qubits
self._num_qubits == other._num_qubits
and np.isclose(self.p_i, other.p_i, atol=atol).item()
and np.isclose(self.p_x, other.p_x, atol=atol).item()
and np.isclose(self.p_y, other.p_y, atol=atol).item()
Expand Down
4 changes: 3 additions & 1 deletion cirq-core/cirq/ops/common_channels_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,8 @@ def test_asymmetric_depolarizing_channel():
)
assert cirq.has_kraus(d)

assert cirq.AsymmetricDepolarizingChannel(p_x=0, p_y=0.1, p_z=0).num_qubits() == 1


def test_asymmetric_depolarizing_mixture():
d = cirq.asymmetric_depolarize(0.1, 0.2, 0.3)
Expand Down Expand Up @@ -729,7 +731,7 @@ def test_default_asymmetric_depolarizing_channel():
assert d.p_x == 0.0
assert d.p_y == 0.0
assert d.p_z == 0.0
assert d.num_qubits == 1
assert d.num_qubits() == 1


def test_bad_error_probabilities_gate():
Expand Down