Call cirq.testing.assert_equivalent_repr for `cirq.SingleQubitCliff…

…ordGate` and `cirq.CliffordTableau` (#5664)

`cirq.CliffordTableau` is represented by `rs`, `xs` and `zs` yet these can't be passed into the `__init__` but are instead calculated and/or set in the class. This PR adds `xs`, `xs`, and `zs` as `Optional` arguments so that the `CliffordTableau` can be reconstructed from the `__repr__`.

Fixes: #5641

cirq-core/cirq/ops/clifford_gate.py

@@ -879,16 +879,7 @@ def equivalent_gate_before(self, after: 'SingleQubitCliffordGate') -> 'SingleQub
         return self.merged_with(after).merged_with(self**-1)
 
     def __repr__(self) -> str:
-        x = self.pauli_tuple(pauli_gates.X)
-        y = self.pauli_tuple(pauli_gates.Y)
-        z = self.pauli_tuple(pauli_gates.Z)
-        x_sign = '-' if x[1] else '+'
-        y_sign = '-' if y[1] else '+'
-        z_sign = '-' if z[1] else '+'
-        return (
-            f'cirq.SingleQubitCliffordGate(X:{x_sign}{x[0]!s}, '
-            f'Y:{y_sign}{y[0]!s}, Z:{z_sign}{z[0]!s})'
-        )
+        return f'cirq.CliffordGate.from_clifford_tableau({self.clifford_tableau!r})'
 
     def _circuit_diagram_info_(
         self, args: 'cirq.CircuitDiagramInfoArgs'

cirq-core/cirq/ops/clifford_gate_test.py

@@ -329,16 +329,22 @@ def test_eq_ne_and_hash():
 
 
 @pytest.mark.parametrize(
-    'gate,rep',
+    'gate',
     (
-        (cirq.SingleQubitCliffordGate.I, 'cirq.SingleQubitCliffordGate(X:+X, Y:+Y, Z:+Z)'),
-        (cirq.SingleQubitCliffordGate.H, 'cirq.SingleQubitCliffordGate(X:+Z, Y:-Y, Z:+X)'),
-        (cirq.SingleQubitCliffordGate.X, 'cirq.SingleQubitCliffordGate(X:+X, Y:-Y, Z:-Z)'),
-        (cirq.SingleQubitCliffordGate.X_sqrt, 'cirq.SingleQubitCliffordGate(X:+X, Y:+Z, Z:-Y)'),
+        cirq.SingleQubitCliffordGate.I,
+        cirq.SingleQubitCliffordGate.H,
+        cirq.SingleQubitCliffordGate.X,
+        cirq.SingleQubitCliffordGate.X_sqrt,
     ),
 )
-def test_repr(gate, rep):
-    assert repr(gate) == rep
+def test_repr_gate(gate):
+    cirq.testing.assert_equivalent_repr(gate)
+
+
+def test_repr_operation():
+    cirq.testing.assert_equivalent_repr(
+        cirq.SingleQubitCliffordGate.from_pauli(cirq.Z).on(cirq.LineQubit(2))
+    )
 
 
 @pytest.mark.parametrize(

cirq-core/cirq/qis/clifford_tableau.py

@@ -17,6 +17,7 @@
 import numpy as np
 
 from cirq import protocols
+from cirq._compat import proper_repr
 from cirq.qis import quantum_state_representation
 from cirq.value import big_endian_int_to_digits, linear_dict
 
@@ -137,30 +138,92 @@ class CliffordTableau(StabilizerState):
     an eigenoperator of the state vector with eigenvalue one: P|psi> = |psi>.
     """
 
-    def __init__(self, num_qubits, initial_state: int = 0):
+    def __init__(
+        self,
+        num_qubits,
+        initial_state: int = 0,
+        rs: Optional[np.ndarray] = None,
+        xs: Optional[np.ndarray] = None,
+        zs: Optional[np.ndarray] = None,
+    ):
         """Initializes CliffordTableau
         Args:
             num_qubits: The number of qubits in the system.
             initial_state: The computational basis representation of the
                 state as a big endian int.
         """
         self.n = num_qubits
-
-        # The last row (`2n+1`-th row) is the scratch row used in _measurement
+        self.initial_state = initial_state
+        # _reconstruct_* adds the last row (`2n+1`-th row) to the input arrays,
+        # which is the scratch row used in _measurement
         # computation process only. It should not be exposed to external usage.
-        self._rs = np.zeros(2 * self.n + 1, dtype=bool)
-
-        for (i, val) in enumerate(
-            big_endian_int_to_digits(initial_state, digit_count=num_qubits, base=2)
-        ):
-            self._rs[self.n + i] = bool(val)
+        self._rs = self._reconstruct_rs(rs)
+        self._xs = self._reconstruct_xs(xs)
+        self._zs = self._reconstruct_zs(zs)
+
+    def _reconstruct_rs(self, rs: Optional[np.ndarray]) -> np.ndarray:
+        if rs is None:
+            new_rs = np.zeros(2 * self.n + 1, dtype=bool)
+            for (i, val) in enumerate(
+                big_endian_int_to_digits(self.initial_state, digit_count=self.n, base=2)
+            ):
+                new_rs[self.n + i] = bool(val)
+        else:
+            shape = rs.shape
+            if len(shape) == 1 and shape[0] == 2 * self.n and rs.dtype == np.dtype(bool):
+                new_rs = np.append(rs, np.zeros(1, dtype=bool))
+            else:
+                raise ValueError(
+                    f"The value you passed for rs is not the correct shape and/or type. "
+                    f"Please confirm that it's a single row with 2*num_qubits columns "
+                    f"and of type bool."
+                )
+        return new_rs
+
+    def _reconstruct_xs(self, xs: Optional[np.ndarray]) -> np.ndarray:
+        if xs is None:
+            new_xs = np.zeros((2 * self.n + 1, self.n), dtype=bool)
+            for i in range(self.n):
+                new_xs[i, i] = True
+        else:
+            shape = xs.shape
+            if (
+                len(shape) == 2
+                and shape[0] == 2 * self.n
+                and shape[1] == self.n
+                and xs.dtype == np.dtype(bool)
+            ):
+                new_xs = np.append(xs, np.zeros((1, self.n), dtype=bool), axis=0)
+            else:
+                raise ValueError(
+                    f"The value you passed for xs is not the correct shape and/or type. "
+                    f"Please confirm that it's 2*num_qubits rows, num_qubits columns, "
+                    f"and of type bool."
+                )
+        return new_xs
 
-        self._xs = np.zeros((2 * self.n + 1, self.n), dtype=bool)
-        self._zs = np.zeros((2 * self.n + 1, self.n), dtype=bool)
+    def _reconstruct_zs(self, zs: Optional[np.ndarray]) -> np.ndarray:
 
-        for i in range(self.n):
-            self._xs[i, i] = True
-            self._zs[self.n + i, i] = True
+        if zs is None:
+            new_zs = np.zeros((2 * self.n + 1, self.n), dtype=bool)
+            for i in range(self.n):
+                new_zs[self.n + i, i] = True
+        else:
+            shape = zs.shape
+            if (
+                len(shape) == 2
+                and shape[0] == 2 * self.n
+                and shape[1] == self.n
+                and zs.dtype == np.dtype(bool)
+            ):
+                new_zs = np.append(zs, np.zeros((1, self.n), dtype=bool), axis=0)
+            else:
+                raise ValueError(
+                    f"The value you passed for zs is not the correct shape and/or type. "
+                    f"Please confirm that it's 2*num_qubits rows, num_qubits columns, "
+                    f"and of type bool."
+                )
+        return new_zs
 
     @property
     def xs(self) -> np.ndarray:
@@ -233,8 +296,13 @@ def copy(self, deep_copy_buffers: bool = True) -> 'CliffordTableau':
         return state
 
     def __repr__(self) -> str:
-        stabilizers = ", ".join([repr(stab) for stab in self.stabilizers()])
-        return f'stabilizers: [{stabilizers}]'
+        return (
+            f"cirq.CliffordTableau({self.n},"
+            f"rs={proper_repr(np.delete(self._rs, len(self._rs)-1))}, "
+            f"xs={proper_repr(np.delete(self._xs, len(self._xs)-1, axis=0))},"
+            f"zs={proper_repr(np.delete(self._zs, len(self._zs)-1, axis=0))}, "
+            f"initial_state={self.initial_state})"
+        )
 
     def __str__(self) -> str:
         string = ''

cirq-core/cirq/qis/clifford_tableau_test.py

@@ -55,6 +55,21 @@ def test_tableau_initial_state_string(num_qubits):
             assert splitted_represent_string[n] == expected_string
 
 
+def test_tableau_invalid_initial_state():
+    with pytest.raises(ValueError, match="2*num_qubits columns and of type bool."):
+        cirq.CliffordTableau(1, rs=np.zeros(1, dtype=bool))
+
+    with pytest.raises(
+        ValueError, match="2*num_qubits rows, num_qubits columns, and of type bool."
+    ):
+        cirq.CliffordTableau(1, xs=np.zeros(1, dtype=bool))
+
+    with pytest.raises(
+        ValueError, match="2*num_qubits rows, num_qubits columns, and of type bool."
+    ):
+        cirq.CliffordTableau(1, zs=np.zeros(1, dtype=bool))
+
+
 def test_stabilizers():
     # Note: the stabilizers are not unique for one state. We just use the one
     # produced by the tableau algorithm.
@@ -271,8 +286,7 @@ def test_str():
 
 
 def test_repr():
-    t = cirq.CliffordTableau(num_qubits=1)
-    assert repr(t) == "stabilizers: [cirq.DensePauliString('Z', coefficient=(1+0j))]"
+    cirq.testing.assert_equivalent_repr(cirq.CliffordTableau(num_qubits=1))
 
 
 def test_str_full():