Implement MatrixGate and simplify __eq__ in BasicGate to improve performance

projectq/backends/_sim/_simulator_test.py

@@ -29,9 +29,9 @@
 from projectq import MainEngine
 from projectq.cengines import (BasicEngine, BasicMapperEngine, DummyEngine,
                                LocalOptimizer, NotYetMeasuredError)
-from projectq.ops import (All, Allocate, BasicGate, MatrixGate, BasicMathGate, CNOT,
-                          Command, H, Measure, QubitOperator, Rx, Ry, Rz, S,
-                          TimeEvolution, Toffoli, X, Y, Z)
+from projectq.ops import (All, Allocate, BasicGate, BasicMathGate, CNOT,
+                          Command, H, MatrixGate, Measure, QubitOperator,
+                          Rx, Ry, Rz, S, TimeEvolution, Toffoli, X, Y, Z)
 from projectq.meta import Control, Dagger, LogicalQubitIDTag
 from projectq.types import WeakQubitRef
 

projectq/ops/_basics.py

@@ -64,7 +64,7 @@ class NotInvertible(Exception):
 
 class BasicGate(object):
     """
-    Base class of all gates.
+    Base class of all gates. (Don't use it directly but derive from it)
     """
     def __init__(self):
         """
@@ -203,20 +203,15 @@ def __or__(self, qubits):
         cmd = self.generate_command(qubits)
         apply_command(cmd)
 
-    @property
-    def matrix(self):
-        raise AttributeError("BasicGate has no matrix property. Use MatrixGate instead.")
-
-    @matrix.setter
-    def matrix(self, matrix=None):
-        raise AttributeError("You cannot set the matrix property of gates derived"
-                             "from BasicGate. Please use MatrixGate instead if"
-                             "you need that functionality.")
-
     def __eq__(self, other):
         """ Return True if equal (i.e., instance of same class).
         """
-        return isinstance(other, self.__class__)
+        if isinstance(other, self.__class__):
+            return True
+        elif isinstance(other, MatrixGate):
+            return NotImplemented
+        else:
+            return False
 
     def __ne__(self, other):
         return not self.__eq__(other)
@@ -227,13 +222,30 @@ def __str__(self):
     def __hash__(self):
         return hash(str(self))
 
+
 class MatrixGate(BasicGate):
     """
-    Defines a base class of a matrix gate.
+    Defines a gate class whose instances are defined by a matrix.
+
+    Note:
+        Use this gate class only for gates acting on a small numbers of qubits.
+        In general, consider instead using one of the provided ProjectQ gates
+        or define a new class as this allows the compiler to work symbolically.
+
+    Example:
+
+        .. code-block:: python
 
-    A matrix gate is defined via its matrix.
+            gate = MatrixGate([[0, 1], [1, 0]])
+            gate | qubit
     """
     def __init__(self, matrix=None):
+        """
+        Initialize MatrixGate
+
+        Args:
+            matrix(numpy.matrix): matrix which defines the gate. Default: None
+        """
         BasicGate.__init__(self)
         self._matrix = np.matrix(matrix) if matrix is not None else None
 
@@ -246,9 +258,7 @@ def matrix(self, matrix):
         self._matrix = np.matrix(matrix)
 
     def __eq__(self, other):
-        """ Return True if equal (i.e., instance of same class).
-        """
-        if not isinstance(other, self.__class__):
+        if not hasattr(other, 'matrix'):
             return False
         if (not isinstance(self.matrix, np.matrix) or
                 not isinstance(other.matrix, np.matrix)):
@@ -262,12 +272,19 @@ def __eq__(self, other):
             return True
         return False
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __str__(self):
-        raise NotImplementedError('This gate does not implement __str__.')
+        return("MatrixGate(" + str(self.matrix.tolist()) + ")")
+
+    def __hash__(self):
+        return hash(str(self))
 
     def get_inverse(self):
         return MatrixGate(np.linalg.inv(self.matrix))
 
+
 class SelfInverseGate(BasicGate):
     """
     Self-inverse basic gate class.

projectq/ops/_basics_test.py

@@ -21,7 +21,7 @@
 import pytest
 
 from projectq.types import Qubit, Qureg
-from projectq.ops import Command
+from projectq.ops import Command, X
 from projectq import MainEngine
 from projectq.cengines import DummyEngine
 
@@ -295,6 +295,7 @@ def __init__(self):
     math_fun = gate.get_math_function(("qreg1", "qreg2", "qreg3"))
     assert math_fun([2, 3, 5]) == [2, 3, 11]
 
+
 def test_matrix_gate():
     gate1 = _basics.MatrixGate()
     gate2 = _basics.MatrixGate()
@@ -321,3 +322,7 @@ def test_matrix_gate():
     gate9 = _basics.MatrixGate([[1, 0], [0, (1-1j)/math.sqrt(2)]])
     gate10 = gate9.get_inverse()
     assert gate10 == gate8
+    assert gate3 == X
+    assert X == gate3
+    assert str(gate3) == "MatrixGate([[0, 1], [1, 0]])"
+    assert hash(gate3) == hash("MatrixGate([[0, 1], [1, 0]])")

projectq/ops/_metagates.py

@@ -28,7 +28,7 @@
 * C (Creates an n-ary controlled version of an arbitrary gate)
 """
 
-from ._basics import BasicGate, MatrixGate, NotInvertible
+from ._basics import BasicGate, NotInvertible
 from ._command import Command, apply_command
 
 
@@ -39,7 +39,7 @@ class ControlQubitError(Exception):
     pass
 
 
-class DaggeredGate(MatrixGate): #todo: do we want this?
+class DaggeredGate(BasicGate):
     """
     Wrapper class allowing to execute the inverse of a gate, even when it does
     not define one.

projectq/setups/decompositions/arb1qubit2rzandry_test.py

@@ -23,8 +23,8 @@
 from projectq.backends import Simulator
 from projectq.cengines import (AutoReplacer, DecompositionRuleSet,
                                DummyEngine, InstructionFilter, MainEngine)
-from projectq.ops import (BasicGate, MatrixGate, ClassicalInstructionGate, Measure, Ph, R,
-                          Rx, Ry, Rz, X)
+from projectq.ops import (BasicGate, ClassicalInstructionGate, MatrixGate,
+                          Measure, Ph, R, Rx, Ry, Rz, X)
 from projectq.meta import Control
 
 from . import arb1qubit2rzandry as arb1q

projectq/setups/decompositions/carb1qubit2cnotrzandry_test.py

@@ -21,8 +21,8 @@
 from projectq.cengines import (AutoReplacer, DecompositionRuleSet,
                                DummyEngine, InstructionFilter, MainEngine)
 from projectq.meta import Control
-from projectq.ops import (All, BasicGate, MatrixGate, ClassicalInstructionGate, Measure,
-                          Ph, R, Rx, Ry, Rz, X, XGate)
+from projectq.ops import (All, BasicGate, ClassicalInstructionGate,
+                          MatrixGate, Measure, Ph, R, Rx, Ry, Rz, X, XGate)
 from projectq.setups.decompositions import arb1qubit2rzandry_test as arb1q_t
 
 from . import carb1qubit2cnotrzandry as carb1q