Merge branch 'main' into fix-backend-v1-pm-config-from

mtreinish · Mar 3, 2023 · 87ed13a · 87ed13a
2 parents 78ef8e8 + 23e30f2
commit 87ed13a
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Showing 2 changed files with 27 additions and 9 deletions.
diff --git a/qiskit/circuit/bit.py b/qiskit/circuit/bit.py
@@ -54,14 +54,23 @@ def __init__(self, register=None, index=None):
 
     @property
     def register(self):
-        """Get bit's register."""
+        """Get the register of an old-style bit.
+
+        .. deprecated:: 0.17
+            Use :meth:`.QuantumCircuit.find_bit` instead.
+
+        In modern Qiskit Terra (version 0.17+), bits are the fundamental object and registers are
+        aliases to collections of bits.  A bit can be in many registers depending on the circuit, so
+        a single containing register is no longer a property of a bit.  It is an error to access
+        this attribute on bits that were not constructed as "owned" by a register."""
         if (self._register, self._index) == (None, None):
             raise CircuitError("Attempt to query register of a new-style Bit.")
 
         warnings.warn(
-            "Back-references to from Bit instances to their containing "
-            "Registers have been deprecated. Instead, inspect Registers "
-            "to find their contained Bits.",
+            "'Bit.register' is deprecated since Qiskit Terra 0.17 and will be removed "
+            "in a future release. Bits may be in more than one register. "
+            "Use 'QuantumCircuit.find_bit' to find all the containing registers within a circuit, "
+            "and the index of the bit within the circuit.",
             DeprecationWarning,
             stacklevel=2,
         )
@@ -70,14 +79,23 @@ def register(self):
 
     @property
     def index(self):
-        """Get bit's index."""
+        """Get the index of an old-style bit in the register that owns it.
+
+        .. deprecated:: 0.17
+            Use :meth:`.QuantumCircuit.find_bit` instead.
+
+        In modern Qiskit Terra (version 0.17+), bits are the fundamental object and registers are
+        aliases to collections of bits.  A bit can be in many registers depending on the circuit, so
+        a single containing register is no longer a property of a bit.  It is an error to access
+        this attribute on bits that were not constructed as "owned" by a register."""
         if (self._register, self._index) == (None, None):
             raise CircuitError("Attempt to query index of a new-style Bit.")
 
         warnings.warn(
-            "Back-references to from Bit instances to their containing "
-            "Registers have been deprecated. Instead, inspect Registers "
-            "to find their contained Bits.",
+            "'Bit.index' is deprecated since Qiskit Terra 0.17 and will be removed "
+            "in a future release. Bits may be in more than one register. "
+            "Use 'QuantumCircuit.find_bit' to find all the containing registers within a circuit, "
+            "and the index of the bit within the circuit.",
             DeprecationWarning,
             stacklevel=2,
         )

diff --git a/qiskit/test/base.py b/qiskit/test/base.py
@@ -211,7 +211,7 @@ def setUpClass(cls):
             r"elementwise comparison failed.*",
             r"The jsonschema validation included in qiskit-terra.*",
             r"The DerivativeBase.parameter_expression_grad method.*",
-            r"Back-references to from Bit instances.*",
+            r"'Bit\.(register|index)' is deprecated.*",
             r"The CXDirection pass has been deprecated",
             r"The pauli_basis function with PauliTable.*",
             # Caused by internal scikit-learn scipy usage