Deprecate qiskit/quantum_info/synthesis and move to qiskit/synthesis

qiskit/circuit/library/generalized_gates/rv.py

@@ -55,10 +55,10 @@ def __init__(self, v_x, v_y, v_z, basis="U"):
             v_y (float): y-component
             v_z (float): z-component
             basis (str, optional): basis (see
-                :class:`~qiskit.quantum_info.synthesis.one_qubit_decompose.OneQubitEulerDecomposer`)
+                :class:`~qiskit.synthesis.one_qubit.one_qubit_decompose.OneQubitEulerDecomposer`)
         """
         # pylint: disable=cyclic-import
-        from qiskit.quantum_info.synthesis.one_qubit_decompose import OneQubitEulerDecomposer
+        from qiskit.synthesis.one_qubit.one_qubit_decompose import OneQubitEulerDecomposer
 
         super().__init__("rv", 1, [v_x, v_y, v_z])
         self._decomposer = OneQubitEulerDecomposer(basis=basis)

qiskit/circuit/library/generalized_gates/uc.py

@@ -35,7 +35,7 @@
 from qiskit.exceptions import QiskitError
 
 # pylint: disable=cyclic-import
-from qiskit.quantum_info.synthesis.one_qubit_decompose import OneQubitEulerDecomposer
+from qiskit.synthesis.one_qubit.one_qubit_decompose import OneQubitEulerDecomposer
 
 from .diagonal import Diagonal
 

qiskit/circuit/library/generalized_gates/unitary.py

@@ -28,8 +28,8 @@
 from qiskit.quantum_info.operators.predicates import is_unitary_matrix
 
 # pylint: disable=cyclic-import
-from qiskit.quantum_info.synthesis.one_qubit_decompose import OneQubitEulerDecomposer
-from qiskit.quantum_info.synthesis.two_qubit_decompose import two_qubit_cnot_decompose
+from qiskit.synthesis.one_qubit.one_qubit_decompose import OneQubitEulerDecomposer
+from qiskit.synthesis.two_qubit.two_qubit_decompose import two_qubit_cnot_decompose
 
 from .isometry import Isometry
 
@@ -146,7 +146,7 @@ def _define(self):
         elif self.num_qubits == 2:
             self.definition = two_qubit_cnot_decompose(self.to_matrix())
         else:
-            from qiskit.quantum_info.synthesis.qsd import (  # pylint: disable=cyclic-import
+            from qiskit.synthesis.unitary.qsd import (  # pylint: disable=cyclic-import
                 qs_decomposition,
             )
 

qiskit/circuit/library/pauli_evolution.py

@@ -19,7 +19,7 @@
 
 from qiskit.circuit.gate import Gate
 from qiskit.circuit.parameterexpression import ParameterExpression
-from qiskit.synthesis import EvolutionSynthesis, LieTrotter
+from qiskit.synthesis.evolution import EvolutionSynthesis, LieTrotter
 from qiskit.quantum_info import Pauli, SparsePauliOp
 
 

qiskit/circuit/library/standard_gates/equivalence_library.py

@@ -26,8 +26,6 @@
     Clbit,
 )
 
-from qiskit.quantum_info.synthesis.ion_decompose import cnot_rxx_decompose
-
 from . import (
     HGate,
     CHGate,
@@ -83,6 +81,38 @@
 _sel = StandardEquivalenceLibrary = EquivalenceLibrary()
 
 
+def _cnot_rxx_decompose(plus_ry: bool = True, plus_rxx: bool = True):
+    """Decomposition of CNOT gate.
+
+    NOTE: this differs to CNOT by a global phase.
+    The matrix returned is given by exp(1j * pi/4) * CNOT
+
+    Args:
+        plus_ry (bool): positive initial RY rotation
+        plus_rxx (bool): positive RXX rotation.
+
+    Returns:
+        QuantumCircuit: The decomposed circuit for CNOT gate (up to
+        global phase).
+    """
+    # Convert boolean args to +/- 1 signs
+    if plus_ry:
+        sgn_ry = 1
+    else:
+        sgn_ry = -1
+    if plus_rxx:
+        sgn_rxx = 1
+    else:
+        sgn_rxx = -1
+    circuit = QuantumCircuit(2, global_phase=-sgn_ry * sgn_rxx * pi / 4)
+    circuit.append(RYGate(sgn_ry * pi / 2), [0])
+    circuit.append(RXXGate(sgn_rxx * pi / 2), [0, 1])
+    circuit.append(RXGate(-sgn_rxx * pi / 2), [0])
+    circuit.append(RXGate(-sgn_rxx * sgn_ry * pi / 2), [1])
+    circuit.append(RYGate(-sgn_ry * pi / 2), [0])
+    return circuit
+
+
 # Import existing gate definitions
 
 # HGate
@@ -1250,9 +1280,9 @@
 
 # CXGate
 
-for plus_ry in [False, True]:
-    for plus_rxx in [False, True]:
-        cx_to_rxx = cnot_rxx_decompose(plus_ry, plus_rxx)
+for pos_ry in [False, True]:
+    for pos_rxx in [False, True]:
+        cx_to_rxx = _cnot_rxx_decompose(pos_ry, pos_rxx)
         _sel.add_equivalence(CXGate(), cx_to_rxx)
 
 # CXGate

qiskit/quantum_info/__init__.py

@@ -74,6 +74,11 @@
 Utility Functions
 =================
 
+.. autosummary::
+   :toctree: ../stubs/
+
+   Quaternion
+
 .. autofunction:: partial_trace
 .. autofunction:: schmidt_decomposition
 .. autofunction:: shannon_entropy
@@ -105,19 +110,6 @@
 
    Z2Symmetries
 
-Synthesis
-=========
-
-.. autosummary::
-   :toctree: ../stubs/
-
-   OneQubitEulerDecomposer
-   TwoQubitBasisDecomposer
-   Quaternion
-   XXDecomposer
-
-.. autofunction:: two_qubit_cnot_decompose
-.. autofunction:: decompose_clifford
 """
 
 from __future__ import annotations
@@ -163,11 +155,27 @@
     state_fidelity,
     negativity,
 )
-from .synthesis import (
-    OneQubitEulerDecomposer,
-    Quaternion,
-    TwoQubitBasisDecomposer,
-    XXDecomposer,
-    decompose_clifford,
-    two_qubit_cnot_decompose,
-)
+from .quaternion import Quaternion
+
+_DEPRECATED_NAMES = {
+    "OneQubitEulerDecomposer": "qiskit.synthesis",
+    "TwoQubitBasisDecomposer": "qiskit.synthesis",
+    "XXDecomposer": "qiskit.synthesis",
+    "two_qubit_cnot_decompose": "qiskit.synthesis",
+}
+
+
+def __getattr__(name):
+    if name in _DEPRECATED_NAMES:
+        import importlib
+        import warnings
+
+        module_name = _DEPRECATED_NAMES[name]
+        warnings.warn(
+            f"Accessing '{name}' from '{__name__}' is deprecated since Qiskit 0.46"
+            f" and will be removed in 1.0.  Import from '{module_name}' instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return getattr(importlib.import_module(module_name), name)
+    raise AttributeError(f"module '{__name__}' has no attribute '{name}'")

qiskit/quantum_info/synthesis/__init__.py

@@ -13,8 +13,18 @@
 """State and Unitary synthesis methods."""
 
 from __future__ import annotations
-from .two_qubit_decompose import TwoQubitBasisDecomposer, two_qubit_cnot_decompose
-from .one_qubit_decompose import OneQubitEulerDecomposer
-from .quaternion import Quaternion
-from .clifford_decompose import decompose_clifford
-from .xx_decompose.decomposer import XXDecomposer
+import warnings
+
+from qiskit.synthesis.one_qubit import OneQubitEulerDecomposer
+from qiskit.synthesis.two_qubit.xx_decompose import XXDecomposer
+from qiskit.synthesis.two_qubit.two_qubit_decompose import (
+    TwoQubitBasisDecomposer,
+    two_qubit_cnot_decompose,
+)
+
+warnings.warn(
+    "The qiskit.quantum_info.synthesis module is deprecated since Qiskit 0.46.0."
+    "It will be removed in the Qiskit 1.0 release.",
+    stacklevel=2,
+    category=DeprecationWarning,
+)

qiskit/quantum_info/synthesis/ion_decompose.py

@@ -21,8 +21,10 @@
 from qiskit.circuit.library.standard_gates.ry import RYGate
 from qiskit.circuit.library.standard_gates.rx import RXGate
 from qiskit.circuit.library.standard_gates.rxx import RXXGate
+from qiskit.utils.deprecation import deprecate_func
 
 
+@deprecate_func(since="0.46.0")
 def cnot_rxx_decompose(plus_ry: bool = True, plus_rxx: bool = True):
     """Decomposition of CNOT gate.
 

qiskit/synthesis/__init__.py

@@ -10,7 +10,7 @@
 # copyright notice, and modified files need to carry a notice indicating
 # that they have been altered from the originals.
 
-"""
+r"""
 ===========================================
 Circuit Synthesis (:mod:`qiskit.synthesis`)
 ===========================================
@@ -94,8 +94,29 @@
 Unitary Synthesis
 =================
 
+Decomposition of general :math:`2^n \times 2^n` unitary matrices for any number of qubits.
+
+.. autofunction:: qs_decomposition
+
 The Approximate Quantum Compiler is available here: :mod:`qiskit.synthesis.unitary.aqc`
 
+One-Qubit Synthesis
+===================
+
+.. autosummary::
+   :toctree: ../stubs/
+
+   OneQubitEulerDecomposer
+
+Two-Qubit Synthesis
+===================
+
+.. autosummary::
+   :toctree: ../stubs/
+
+   TwoQubitBasisDecomposer
+   XXDecomposer
+
 """
 
 from .evolution import (
@@ -137,4 +158,8 @@
 )
 from .discrete_basis import SolovayKitaevDecomposition, generate_basic_approximations
 from .qft import synth_qft_line
+from .unitary.qsd import qs_decomposition
 from .unitary import aqc
+from .one_qubit import OneQubitEulerDecomposer
+from .two_qubit.xx_decompose import XXDecomposer
+from .two_qubit.two_qubit_decompose import TwoQubitBasisDecomposer, two_qubit_cnot_decompose

qiskit/synthesis/one_qubit/__init__.py

@@ -0,0 +1,15 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2017, 2023.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Module containing one qubit unitary synthesis methods."""
+
+from .one_qubit_decompose import OneQubitEulerDecomposer