Replace qubit_pauli_string with qubit_pauli_tensor (#200)

qermit/noise_model/noise_model.py

@@ -409,7 +409,7 @@ def distribution(self) -> Dict[QubitPauliString, float]:
         distribution: Dict[QubitPauliString, float] = {}
         for stab, count in dict(self.pauli_error_counter).items():
             # Note that the phase is ignored here
-            pauli_string, _ = stab.qubit_pauli_string
+            pauli_string = stab.qubit_pauli_tensor.string
             distribution[pauli_string] = (
                 distribution.get(pauli_string, 0) + count / self.total
             )

qermit/noise_model/qermit_pauli.py

@@ -7,7 +7,7 @@
 import numpy as np
 from numpy.random import Generator
 from pytket.circuit import Circuit, OpType, Qubit
-from pytket.pauli import Pauli, QubitPauliString
+from pytket.pauli import Pauli, QubitPauliString, QubitPauliTensor
 
 
 class QermitPauli:
@@ -208,8 +208,7 @@ def __hash__(self):
         return hash(key)
 
     def __str__(self) -> str:
-        qubit_pauli_string, operator_phase = self.qubit_pauli_string
-        return f"{qubit_pauli_string}, {operator_phase}"
+        return str(self.qubit_pauli_tensor)
 
     def __eq__(self, other: object) -> bool:
         """Checks for equality by checking all qubits match, and that all
@@ -538,10 +537,10 @@ def circuit(self) -> Circuit:
         return circ
 
     @property
-    def pauli_string(self) -> Tuple[List[Pauli], complex]:
-        """List of Paulis which correspond to Pauli, and the phase.
+    def qubit_pauli_tensor(self) -> QubitPauliTensor:
+        """Return QubitPauliTensor describing Pauli.
 
-        :return: [description]
+        :return: QubitPauliTensor describing Pauli.
         """
 
         operator_phase = self.phase
@@ -558,21 +557,11 @@ def pauli_string(self) -> Tuple[List[Pauli], complex]:
                 operator_phase += 3
                 operator_phase %= 4
 
-        return paulis, self.phase_dict[operator_phase]
-
-    @property
-    def qubit_pauli_string(self) -> Tuple[QubitPauliString, complex]:
-        """Qubit pauli string corresponding to Pauli,
-        along with the appropriate phase.
-
-        :return: Pauli string and phase corresponding to Pauli.
-        """
-
-        paulis, operator_phase = self.pauli_string
-
-        qubit_pauli_string = QubitPauliString(qubits=self.qubit_list, paulis=paulis)
-
-        return qubit_pauli_string, operator_phase
+        return QubitPauliTensor(
+            qubits=self.qubit_list,
+            paulis=paulis,
+            coeff=self.phase_dict[operator_phase],
+        )
 
     @classmethod
     def from_pauli_iterable(

tests/coherent_pauli_checks_test.py

@@ -336,12 +336,11 @@ def test_logical_error_coherent_pauli_check_workflow():
     )
 
     pauli_sampler = OptimalPauliSampler(noise_model=noise_model, n_checks=1)
-    assert pauli_sampler.sample(circ=cliff_sub_circ)[0].qubit_pauli_string == (
-        QubitPauliString(
-            qubits=[Qubit(0), Qubit(1), Qubit(2)], paulis=[Pauli.I, Pauli.I, Pauli.Z]
-        ),
-        1,
+    pauli = pauli_sampler.sample(circ=cliff_sub_circ)[0]
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
+        qubits=[Qubit(0), Qubit(1), Qubit(2)], paulis=[Pauli.I, Pauli.I, Pauli.Z]
     )
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     cliff_circ = Circuit()
     cliff_circ.add_q_register(name="my_reg", size=3)

tests/noise_model_test.py

@@ -108,7 +108,8 @@ def test_qermit_pauli_from_iterable() -> None:
         pauli_iterable=qubit_pauli_string.map.values(),
         qubit_list=list(qubit_pauli_string.map.keys()),
     )
-    pauli.qubit_pauli_string == (qubit_pauli_string, 1 + 0j)
+    pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    pauli.qubit_pauli_tensor.coeff == 1 + 0j
 
 
 def test_qermit_pauli_commute_coeff() -> None:
@@ -606,26 +607,27 @@ def test_identity_clifford() -> None:
     )
     pauli.apply_circuit(circ)
 
-    qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qubit_pauli_string == QubitPauliString(
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.Z, Pauli.Z]
     )
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
 
 def test_H() -> None:
     qubit_list = [Qubit(0)]
     pauli = QermitPauli(Z_list=[1], X_list=[0], qubit_list=qubit_list)
 
     pauli.H(qubit=qubit_list[0])
-    qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qubit_pauli_string == QubitPauliString(qubits=qubit_list, paulis=[Pauli.X])
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
+        qubits=qubit_list, paulis=[Pauli.X]
+    )
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.H(qubit=qubit_list[0])
-    qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qubit_pauli_string == QubitPauliString(qubits=qubit_list, paulis=[Pauli.Z])
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
+        qubits=qubit_list, paulis=[Pauli.Z]
+    )
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
 
 def test_h_series_gates() -> None:
@@ -643,11 +645,10 @@ def test_apply_circuit() -> None:
 
     pauli.apply_circuit(circ)
 
-    qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qubit_pauli_string == QubitPauliString(
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.Y]
     )
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
 
 def test_apply_gate() -> None:
@@ -660,11 +661,10 @@ def test_apply_gate() -> None:
 
     pauli.apply_gate(op_type=OpType.H, qubits=[qubit_list[0]])
 
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == QubitPauliString(
+    assert pauli.qubit_pauli_tensor.string == QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.Z, Pauli.Z]
     )
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.apply_gate(
         op_type=OpType.CX,
@@ -674,15 +674,13 @@ def test_apply_gate() -> None:
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.I, Pauli.Z]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.apply_gate(op_type=OpType.S, qubits=[qubit_list[1]])
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
 
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
 
 def test_qubit_pauli_string() -> None:
@@ -696,47 +694,42 @@ def test_qubit_pauli_string() -> None:
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.Z, Pauli.Z, Pauli.Z]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.H(qubit_list[0])
     pauli.S(qubit_list[0])
 
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.Y, Pauli.Z, Pauli.Z]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.CX(qubit_list[0], qubit_list[1])
 
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.Y, Pauli.Z]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == 1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == 1
 
     pauli.S(qubit_list[1])
 
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.X, Pauli.Z]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == -1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == -1
 
     pauli.S(qubit_list[0])
     pauli.CX(qubit_list[0], qubit_list[2])
 
     qubit_pauli_string = QubitPauliString(
         qubits=qubit_list, paulis=[Pauli.X, Pauli.X, Pauli.Y]
     )
-    qermit_qubit_pauli_string, phase = pauli.qubit_pauli_string
-    assert qermit_qubit_pauli_string == qubit_pauli_string
-    assert phase == -1
+    assert pauli.qubit_pauli_tensor.string == qubit_pauli_string
+    assert pauli.qubit_pauli_tensor.coeff == -1
 
 
 def test_clifford_incremental() -> None:
@@ -801,9 +794,8 @@ def test_to_from_qps() -> None:
         paulis=paulis,
     )
     stab = QermitPauli.from_qubit_pauli_string(qubit_pauli_string)
-    stab_qps, stab_phase = stab.qubit_pauli_string
-    assert stab_qps == qubit_pauli_string
-    assert stab_phase == 1 + 0j
+    assert stab.qubit_pauli_tensor.string == qubit_pauli_string
+    assert stab.qubit_pauli_tensor.coeff == 1 + 0j
 
 
 def test_is_measureable() -> None: