This circuit creates two Bell pairs and attempts to perform entanglement purification before measuring the qubits.
```python
from qiskit import *
# Create a circuit with 4 qubits and 2 classical bits
qc = QuantumCircuit(4, 2)
# Step 1: Create two Bell pairs between Alice and Bob
qc.h(0)
qc.cx(0, 1)
qc.h(2)
qc.cx(2, 3)
# Step 2: Perform entanglement purification
qc.cx(0, 2)
qc.cx(1, 3)
qc.h(0)
qc.h(2)
# Step 3: Measure qubits to detect and correct errors
qc.measure(0, 0)
qc.measure(2, 1)
```'Failed to run program: \'409 Client Error: Conflict for url: https://api.quantum.ibm.com/runtime/jobs. {"errors":[{"message":"You have reached the limit of 3 pending jobs. Please wait for a job to complete or cancel one before submitting anything new.","code":3458,"solution":"Wait until some previous jobs were finished. You can cancel pending jobs to run new jobs.","more_info":"https://docs.quantum-computing.ibm.com/errors"}]}\''