mirror of https://github.com/Qiskit/qiskit.git
Improve reverse_bits to support registerless bits (#7423)
* Improve reverse_bits to support registerless bits * Change the algorithm of reverse_bits * Reimplement reverse_bits with reversed bits Also add more test cases. * Simplify bit lookups Co-authored-by: Jake Lishman <jake.lishman@ibm.com>
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Jintao YU
GitHub
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@ -475,37 +475,51 @@ class QuantumCircuit:
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.. parsed-literal::
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┌───┐
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q_0: ┤ H ├─────■──────
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└───┘┌────┴─────┐
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q_1: ─────┤ RX(1.57) ├
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└──────────┘
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a_0: ┤ H ├──■─────────────────
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└───┘┌─┴─┐
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a_1: ─────┤ X ├──■────────────
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└───┘┌─┴─┐
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a_2: ──────────┤ X ├──■───────
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└───┘┌─┴─┐
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b_0: ───────────────┤ X ├──■──
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└───┘┌─┴─┐
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b_1: ────────────────────┤ X ├
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└───┘
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output:
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.. parsed-literal::
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┌──────────┐
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q_0: ─────┤ RX(1.57) ├
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┌───┐└────┬─────┘
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q_1: ┤ H ├─────■──────
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┌───┐
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b_0: ────────────────────┤ X ├
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┌───┐└─┬─┘
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b_1: ───────────────┤ X ├──■──
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┌───┐└─┬─┘
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a_0: ──────────┤ X ├──■───────
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┌───┐└─┬─┘
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a_1: ─────┤ X ├──■────────────
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┌───┐└─┬─┘
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a_2: ┤ H ├──■─────────────────
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└───┘
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"""
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circ = QuantumCircuit(
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*reversed(self.qregs),
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*reversed(self.cregs),
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list(reversed(self.qubits)),
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list(reversed(self.clbits)),
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name=self.name,
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global_phase=self.global_phase,
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)
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num_qubits = self.num_qubits
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num_clbits = self.num_clbits
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old_qubits = self.qubits
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old_clbits = self.clbits
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new_qubits = circ.qubits
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new_clbits = circ.clbits
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new_qubit_map = circ.qubits[::-1]
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new_clbit_map = circ.clbits[::-1]
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for reg in reversed(self.qregs):
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bits = [new_qubit_map[self.find_bit(qubit).index] for qubit in reversed(reg)]
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circ.add_register(QuantumRegister(bits=bits, name=reg.name))
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for reg in reversed(self.cregs):
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bits = [new_clbit_map[self.find_bit(clbit).index] for clbit in reversed(reg)]
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circ.add_register(ClassicalRegister(bits=bits, name=reg.name))
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for inst, qargs, cargs in self.data:
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new_qargs = [new_qubits[num_qubits - old_qubits.index(q) - 1] for q in qargs]
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new_cargs = [new_clbits[num_clbits - old_clbits.index(c) - 1] for c in cargs]
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new_qargs = [new_qubit_map[self.find_bit(qubit).index] for qubit in qargs]
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new_cargs = [new_clbit_map[self.find_bit(clbit).index] for clbit in cargs]
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circ._append(inst, new_qargs, new_cargs)
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return circ
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@ -0,0 +1,11 @@
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---
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fixes:
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- |
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Fixed :meth:`.QuantumCircuit.reverse_bits` with circuits containing registerless
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:class:`.Qubit` and :class:`.Clbit`. For example, the following will now work::
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from qiskit.circuit import QuantumCircuit, Qubit, Clbit
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qc = QuantumCircuit([Qubit(), Clbit()])
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qc.h(0).c_if(qc.clbits[0], 0)
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qc.reverse_bits()
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@ -1008,6 +1008,80 @@ class TestCircuitOperations(QiskitTestCase):
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self.assertEqual(qc.reverse_bits(), expected)
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def test_reverse_bits_with_overlapped_registers(self):
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"""Test reversing order of bits when registers are overlapped."""
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qr1 = QuantumRegister(2, "a")
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qr2 = QuantumRegister(bits=[qr1[0], qr1[1], Qubit()], name="b")
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qc = QuantumCircuit(qr1, qr2)
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qc.h(qr1[0])
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qc.cx(qr1[0], qr1[1])
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qc.cx(qr1[1], qr2[2])
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qr2 = QuantumRegister(bits=[Qubit(), qr1[0], qr1[1]], name="b")
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expected = QuantumCircuit(qr2, qr1)
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expected.h(qr1[1])
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expected.cx(qr1[1], qr1[0])
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expected.cx(qr1[0], qr2[0])
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self.assertEqual(qc.reverse_bits(), expected)
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def test_reverse_bits_with_registerless_bits(self):
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"""Test reversing order of registerless bits."""
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q0 = Qubit()
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q1 = Qubit()
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c0 = Clbit()
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c1 = Clbit()
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qc = QuantumCircuit([q0, q1], [c0, c1])
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qc.h(0)
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qc.cx(0, 1)
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qc.x(0).c_if(1, True)
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qc.measure(0, 0)
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expected = QuantumCircuit([c1, c0], [q1, q0])
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expected.h(1)
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expected.cx(1, 0)
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expected.x(1).c_if(0, True)
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expected.measure(1, 1)
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self.assertEqual(qc.reverse_bits(), expected)
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def test_reverse_bits_with_registers_and_bits(self):
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"""Test reversing order of bits with registers and registerless bits."""
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qr = QuantumRegister(2, "a")
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q = Qubit()
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qc = QuantumCircuit(qr, [q])
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qc.h(qr[0])
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qc.cx(qr[0], qr[1])
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qc.cx(qr[1], q)
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expected = QuantumCircuit([q], qr)
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expected.h(qr[1])
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expected.cx(qr[1], qr[0])
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expected.cx(qr[0], q)
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self.assertEqual(qc.reverse_bits(), expected)
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def test_reverse_bits_with_mixed_overlapped_registers(self):
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"""Test reversing order of bits with overlapped registers and registerless bits."""
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q = Qubit()
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qr1 = QuantumRegister(bits=[q, Qubit()], name="qr1")
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qr2 = QuantumRegister(bits=[qr1[1], Qubit()], name="qr2")
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qc = QuantumCircuit(qr1, qr2, [Qubit()])
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qc.h(q)
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qc.cx(qr1[0], qr1[1])
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qc.cx(qr1[1], qr2[1])
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qc.cx(2, 3)
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qr2 = QuantumRegister(2, "qr2")
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qr1 = QuantumRegister(bits=[qr2[1], q], name="qr1")
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expected = QuantumCircuit([Qubit()], qr2, qr1)
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expected.h(qr1[1])
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expected.cx(qr1[1], qr1[0])
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expected.cx(qr1[0], qr2[0])
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expected.cx(1, 0)
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self.assertEqual(qc.reverse_bits(), expected)
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def test_cnot_alias(self):
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"""Test that the cnot method alias adds a cx gate."""
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qc = QuantumCircuit(2)
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