def test_direction_flip(self):
""" Flip a CX
qr0:----.----
|
qr1:---(+)---
CouplingMap map: [0] -> [1]
qr0:-[H]-(+)-[H]--
|
qr1:-[H]--.--[H]--
"""
qr = QuantumRegister(2, 'qr')
circuit = QuantumCircuit(qr)
circuit.cx(qr[1], qr[0])
coupling = CouplingMap([(0, 1)])
dag = circuit_to_dag(circuit)
expected = QuantumCircuit(qr)
expected.h(qr[0])
expected.h(qr[1])
expected.cx(qr[0], qr[1])
expected.h(qr[0])
expected.h(qr[1])
pass_ = CXDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
def test_direction_error(self):
""" The mapping cannot be fixed by direction mapper
qr0:---------
qr1:---(+)---
|
qr2:----.----
CouplingMap map: [2] <- [0] -> [1]
"""
qr = QuantumRegister(3, 'qr')
circuit = QuantumCircuit(qr)
circuit.cx(qr[1], qr[2])
coupling = CouplingMap([(0, 1), (0, 2)])
dag = circuit_to_dag(circuit)
pass_ = CXDirection(coupling)
with self.assertRaises(TranspilerError):
pass_.run(dag)
def test_preserves_conditions(self):
"""Verify CXDirection preserves conditional on CX gates.
┌───┐ ┌───┐
q_0: |0>───■────┤ X ├───■──┤ X ├
┌─┴─┐ └─┬─┘ ┌─┴─┐└─┬─┘
q_1: |0>─┤ X ├────■───┤ X ├──■──
└─┬─┘ │ └───┘
┌──┴──┐┌──┴──┐
c_0: 0 ╡ = 0 ╞╡ = 0 ╞══════════
└─────┘└─────┘
"""
qr = QuantumRegister(2, 'q')
cr = ClassicalRegister(1, 'c')
circuit = QuantumCircuit(qr, cr)
circuit.cx(qr[0], qr[1]).c_if(cr, 0)
circuit.cx(qr[1], qr[0]).c_if(cr, 0)
circuit.cx(qr[0], qr[1])
circuit.cx(qr[1], qr[0])
coupling = CouplingMap([[0, 1]])
dag = circuit_to_dag(circuit)
expected = QuantumCircuit(qr, cr)
expected.cx(qr[0], qr[1]).c_if(cr, 0)
# Ordering of u2 is important because DAG comparison will consider
# different conditional order on a creg to be a different circuit.
# See https://github.com/Qiskit/qiskit-terra/issues/3164
expected.append(U2Gate(0, pi), [[qr[1], qr[0]]]).c_if(cr, 0)
expected.cx(qr[0], qr[1]).c_if(cr, 0)
expected.append(U2Gate(0, pi), [[qr[1], qr[0]]]).c_if(cr, 0)
expected.cx(qr[0], qr[1])
expected.append(U2Gate(0, pi), [[qr[1], qr[0]]])
expected.cx(qr[0], qr[1])
expected.append(U2Gate(0, pi), [[qr[1], qr[0]]])
pass_ = CXDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
def test_direction_correct(self):
""" The CX is in the right direction
qr0:---(+)---
|
qr1:----.----
CouplingMap map: [0] -> [1]
"""
qr = QuantumRegister(2, 'qr')
circuit = QuantumCircuit(qr)
circuit.cx(qr[0], qr[1])
coupling = CouplingMap([(0, 1)])
dag = circuit_to_dag(circuit)
pass_ = CXDirection(coupling)
after = pass_.run(dag)
self.assertEqual(dag, after)
def test_no_cnots(self):
""" Trivial map in a circuit without entanglement
qr0:---[H]---
qr1:---[H]---
qr2:---[H]---
CouplingMap map: None
"""
qr = QuantumRegister(3, 'qr')
circuit = QuantumCircuit(qr)
circuit.h(qr)
coupling = CouplingMap()
dag = circuit_to_dag(circuit)
pass_ = CXDirection(coupling)
after = pass_.run(dag)
self.assertEqual(dag, after)
def test_flip_with_measure(self):
"""
qr0: -(+)-[m]-
| |
qr1: --.---|--
|
cr0: ------.--
CouplingMap map: [0] -> [1]
qr0: -[H]--.--[H]-[m]-
| |
qr1: -[H]-(+)-[H]--|--
|
cr0: --------------.--
"""
qr = QuantumRegister(2, 'qr')
cr = ClassicalRegister(1, 'cr')
circuit = QuantumCircuit(qr, cr)
circuit.cx(qr[1], qr[0])
circuit.measure(qr[0], cr[0])
coupling = CouplingMap([(0, 1)])
dag = circuit_to_dag(circuit)
expected = QuantumCircuit(qr, cr)
expected.h(qr[0])
expected.h(qr[1])
expected.cx(qr[0], qr[1])
expected.h(qr[0])
expected.h(qr[1])
expected.measure(qr[0], cr[0])
pass_ = CXDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
