Remove unnecessary use of circuit.propagatos() (#226)

`QubitCircuit.compute_unitary()` is faster and saves memory.

src/qutip_qip/qasm.py

@@ -774,7 +774,7 @@ def _gate_add(
             self._custom_gate(
                 qc_temp, [command[0], args, [str(i) for i in range(n)]]
             )
-            unitary_mat = gate_sequence_product(qc_temp.propagators())
+            unitary_mat = qc_temp.compute_unitary()
             custom_gates[gate_name] = unitary_mat
 
         qc.user_gates = custom_gates

tests/test_circuit.py

@@ -102,9 +102,9 @@ class TestQubitCircuit:
     def testresolve(self, gate_from, gate_to, targets, controls):
         qc1 = QubitCircuit(2)
         qc1.add_gate(gate_from, targets=targets, controls=controls)
-        U1 = gate_sequence_product(qc1.propagators())
+        U1 = qc1.compute_unitary()
         qc2 = qc1.resolve_gates(basis=gate_to)
-        U2 = gate_sequence_product(qc2.propagators())
+        U2 = qc2.compute_unitary()
         assert _op_dist(U1, U2) < 1e-12
 
     def testSNOTdecompose(self):
@@ -114,9 +114,9 @@ def testSNOTdecompose(self):
         """
         qc1 = QubitCircuit(1)
         qc1.add_gate("SNOT", targets=0)
-        U1 = gate_sequence_product(qc1.propagators())
+        U1 = qc1.compute_unitary()
         qc2 = qc1.resolve_gates()
-        U2 = gate_sequence_product(qc2.propagators())
+        U2 = qc2.compute_unitary()
         assert _op_dist(U1, U2) < 1e-12
 
     def testFREDKINdecompose(self):
@@ -126,9 +126,9 @@ def testFREDKINdecompose(self):
         """
         qc1 = QubitCircuit(3)
         qc1.add_gate("FREDKIN", targets=[0, 1], controls=[2])
-        U1 = gate_sequence_product(qc1.propagators())
+        U1 = qc1.compute_unitary()
         qc2 = qc1.resolve_gates()
-        U2 = gate_sequence_product(qc2.propagators())
+        U2 = qc2.compute_unitary()
         assert _op_dist(U1, U2) < 1e-12
 
     def testadjacentgates(self):
@@ -138,10 +138,10 @@ def testadjacentgates(self):
         """
         qc1 = QubitCircuit(3)
         qc1.add_gate("ISWAP", targets=[0, 2])
-        U1 = gate_sequence_product(qc1.propagators())
+        U1 = qc1.compute_unitary()
         qc0 = qc1.adjacent_gates()
         qc2 = qc0.resolve_gates(basis="ISWAP")
-        U2 = gate_sequence_product(qc2.propagators())
+        U2 = qc2.compute_unitary()
         assert _op_dist(U1, U2) < 1e-12
 
     def test_add_gate(self):

tests/test_device.py

@@ -76,7 +76,7 @@ def test_device_against_gate_sequence(
     circuit = QubitCircuit(num_qubits)
     for gate in gates:
         circuit.add_gate(gate)
-    U_ideal = gate_sequence_product(circuit.propagators())
+    U_ideal = circuit.compute_unitary()
 
     device = device_class(num_qubits)
     U_physical = gate_sequence_product(device.run(circuit))
@@ -91,7 +91,7 @@ def test_analytical_evolution(num_qubits, gates, device_class, kwargs):
         circuit.add_gate(gate)
     state = qutip.rand_ket(2**num_qubits)
     state.dims = [[2]*num_qubits, [1]*num_qubits]
-    ideal = gate_sequence_product([state] + circuit.propagators())
+    ideal = circuit.run(state)
     device = device_class(num_qubits)
     operators = device.run_state(init_state=state, qc=circuit, analytical=True)
     result = gate_sequence_product(operators)
@@ -112,7 +112,7 @@ def test_numerical_evolution(
 
     state = qutip.rand_ket(2**num_qubits)
     state.dims = [[2]*num_qubits, [1]*num_qubits]
-    target = gate_sequence_product([state] + circuit.propagators())
+    target = circuit.run(state)
     if isinstance(device, DispersiveCavityQED):
         num_ancilla = len(device.dims)-num_qubits
         ancilla_indices = slice(0, num_ancilla)
@@ -169,7 +169,7 @@ def test_numerical_circuit(circuit, device_class, kwargs, schedule_mode):
 
     state = qutip.rand_ket(2**num_qubits)
     state.dims = [[2]*num_qubits, [1]*num_qubits]
-    target = gate_sequence_product([state] + circuit.propagators())
+    target = circuit.run(state)
     if isinstance(device, DispersiveCavityQED):
         num_ancilla = len(device.dims)-num_qubits
         ancilla_indices = slice(0, num_ancilla)

tests/test_optpulseprocessor.py

@@ -102,7 +102,7 @@ def test_multi_gates(self):
 
         rho0 = rand_ket(4)  # use random generated ket state
         rho0.dims = [[2, 2], [1, 1]]
-        U = gate_sequence_product(qc.propagators())
+        U = qc.compute_unitary()
         rho1 = U * rho0
         result = test.run_state(rho0)
         assert_(fidelity(result.states[-1], rho1) > 1-1.0e-6)

tests/test_scheduler.py

@@ -13,12 +13,12 @@ def _verify_scheduled_circuit(circuit, gate_cycle_indices):
     The input gate_cycle_indices is the scheduling result,
     i.e., a list of integers denoting the execution cycle of each gate in the circuit.
     """
-    result0 = gate_sequence_product(circuit.propagators())
+    result0 = circuit.compute_unitary()
     scheduled_gate = [[] for i in range(max(gate_cycle_indices) + 1)]
     for i, cycles in enumerate(gate_cycle_indices):
         scheduled_gate[cycles].append(circuit.gates[i])
     circuit.gates = sum(scheduled_gate, [])
-    result1 = gate_sequence_product(circuit.propagators())
+    result1 = circuit.compute_unitary()
     return tracedist(result0 * result1.dag(), qeye(result0.dims[0])) < 1.0e-7
 
 
@@ -27,7 +27,6 @@ def test_allow_permutation():
     circuit.add_gate("X", 0)
     circuit.add_gate("CNOT", 0, 1)
     circuit.add_gate("X", 1)
-    result0 = gate_sequence_product(circuit.propagators())
 
     scheduler = Scheduler("ASAP", allow_permutation=True)
     gate_cycle_indices = scheduler.schedule(circuit)
@@ -138,7 +137,6 @@ def test_scheduling_gates1(
         repeat_num = 5
     else:
         repeat_num = 0
-    result0 = gate_sequence_product(circuit.propagators())
 
     # run the scheduler
     scheduler = Scheduler(method)
@@ -168,7 +166,6 @@ def test_scheduling_gates2(
         repeat_num = 5
     else:
         repeat_num = 0
-    result0 = gate_sequence_product(circuit.propagators())
 
     # run the scheduler
     scheduler = Scheduler(method)
@@ -200,7 +197,6 @@ def test_scheduling_gates3(
         repeat_num = 5
     else:
         repeat_num = 0
-    result0 = gate_sequence_product(circuit.propagators())
 
     # run the scheduler
     scheduler = Scheduler(method)
@@ -232,7 +228,6 @@ def test_scheduling_gates4(
         repeat_num = 5
     else:
         repeat_num = 0
-    result0 = gate_sequence_product(circuit.propagators())
 
     # run the scheduler
     scheduler = Scheduler(method)
@@ -278,7 +273,6 @@ def test_scheduling_pulse(
         repeat_num = 5
     else:
         repeat_num = 0
-    result0 = gate_sequence_product(circuit.propagators())
 
     # run the scheduler
     scheduler = Scheduler(method)