Qiskit
`ConsolidateBlocks` fails when circuit contains measure and `crx`, `ch`, `rx` combined
Environment
- Qiskit version: 2.1.0
- Python version: Python 3.13.2
- Operating system: Ubuntu 20.04.6 LTS
What is happening?
When running a PassManager that includes Collect2qBlocks, TemplateOptimization, and ConsolidateBlocks on a circuit that includes rx, ch, and crx gates and measurements, the optimization fails with a QiskitError: 'Cannot apply Operation: measure'.
How can we reproduce the issue?
To reproduce:
from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister, transpile
from qiskit_aer import Aer
from qiskit.transpiler.passes import *
from qiskit.transpiler import PassManager
qreg = QuantumRegister(4)
creg = ClassicalRegister(4)
qc = QuantumCircuit(qreg, creg)
qc.rx(0.39269908169872414, 0)
qc.ch(3, 0)
qc.crx(0.7853981633974483, 0, 3)
qc.measure(qreg[0], creg[0])
qc.measure(qreg[1], creg[1])
qc.measure(qreg[2], creg[2])
qc.measure(qreg[3], creg[3])
simulator = Aer.get_backend("aer_simulator")
p = PassManager([Collect2qBlocks(), TemplateOptimization(), ConsolidateBlocks()])
qc = p.run(qc)
compiled_circuit = transpile(qc, backend=simulator)
job = simulator.run(compiled_circuit, shots=500)
result = job.result().get_counts()
print(result)
By the way, removing any one of:
- The
rx,ch, orcrxgate - The measure operations
- One of the passes from the
PassManager
will make the circuit run successfully.
What should happen?
The circuit should transpile and execute successfully.
Any suggestions?
There is also a longer version of the buggy program that can reliably trigger the error. Interestingly, commenting out any one of the marked lines will make the bug disappear:
from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister, transpile
from qiskit_aer import Aer
from qiskit.transpiler.passes import *
from qiskit.circuit.library import *
from qiskit.transpiler import PassManager
import numpy as np
np.random.seed(42)
qreg = QuantumRegister(4)
creg = ClassicalRegister(4)
qc = QuantumCircuit(qreg, creg)
qc.ch(2, 1) # this line
qc.z(2) # this line
qc.rx(0.39269908169872414, 0) # this line
qc.ch(3, 0) # this line
qc.crx(0.7853981633974483, 0, 3) # this line
qr = QuantumRegister(2)
cr = ClassicalRegister(2)
qc.add_register(qr)
qc.add_register(cr)
qc.h(qr[0])
qc.cx(qr[0], qr[1])
qc.measure(qr[0], cr[0])
qc.measure(qr[1], cr[1])
qc.measure(qreg[0], creg[0])
qc.measure(qreg[1], creg[1])
qc.measure(qreg[2], creg[2])
qc.measure(qreg[3], creg[3])
simulator = Aer.get_backend("aer_simulator")
p = PassManager([Collect2qBlocks(), TemplateOptimization(), ConsolidateBlocks()])
qc = p.run(qc)
compiled_circuit = transpile(qc, backend=simulator)
job = simulator.run(compiled_circuit, shots=500)
result = job.result().get_counts()
print(result)
This is most likely the same problem with your code as #14646. You're doing an analysis, invalidating it, then attempting to use the analysis.
