def test_ecr_flip(self):
"""Flip a ECR gate.
┌──────┐
q_0: ┤1 ├
│ ECR │
q_1: ┤0 ├
└──────┘
CouplingMap map: [0, 1]
"""
qr = QuantumRegister(2, "qr")
circuit = QuantumCircuit(qr)
circuit.ecr(qr[1], qr[0])
coupling = CouplingMap([[0, 1]])
dag = circuit_to_dag(circuit)
expected = QuantumCircuit(qr)
expected.ry(pi / 2, qr[0])
expected.ry(-pi / 2, qr[1])
expected.ecr(qr[0], qr[1])
expected.h(qr[0])
expected.h(qr[1])
pass_ = GateDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
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_ = GateDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
def test_preserves_conditions(self):
"""Verify GateDirection 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)
# ┌───┐ ┌───┐ ┌───┐ ┌───┐
# q_0: ───■───────────┤ H ├────■───────────┤ H ├───■──┤ H ├──■──┤ H ├
# ┌─┴─┐ ┌───┐ └─╥─┘ ┌─┴─┐ ┌───┐ └─╥─┘ ┌─┴─┐├───┤┌─┴─┐├───┤
# q_1: ─┤ X ├──┤ H ├────╫────┤ X ├──┤ H ├────╫───┤ X ├┤ H ├┤ X ├┤ H ├
# └─╥─┘ └─╥─┘ ║ └─╥─┘ └─╥─┘ ║ └───┘└───┘└───┘└───┘
# ┌──╨──┐┌──╨──┐┌──╨──┐┌──╨──┐┌──╨──┐┌──╨──┐
# c: 1/╡ 0x0 ╞╡ 0x0 ╞╡ 0x0 ╞╡ 0x0 ╞╡ 0x0 ╞╡ 0x0 ╞════════════════════
# └─────┘└─────┘└─────┘└─────┘└─────┘└─────┘
expected = QuantumCircuit(qr, cr)
expected.cx(qr[0], qr[1]).c_if(cr, 0)
# Order of H gates 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.h(qr[1]).c_if(cr, 0)
expected.h(qr[0]).c_if(cr, 0)
expected.cx(qr[0], qr[1]).c_if(cr, 0)
expected.h(qr[1]).c_if(cr, 0)
expected.h(qr[0]).c_if(cr, 0)
expected.cx(qr[0], qr[1])
expected.h(qr[1])
expected.h(qr[0])
expected.cx(qr[0], qr[1])
expected.h(qr[1])
expected.h(qr[0])
pass_ = GateDirection(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_ = GateDirection(coupling)
with self.assertRaises(TranspilerError):
pass_.run(dag)
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_ = GateDirection(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_ = GateDirection(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_ = GateDirection(coupling)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)