This circuit prepares a 7-qubit state using the Steane code, introduces a bit-flip error on one qubit, decodes the state and performs a measurement.
```python
from qiskit import QuantumCircuit
# Create a quantum circuit with 7 qubits and 7 classical bits
qc = QuantumCircuit(7, 7)
# Encoding step using the 7-qubit Steane code
# Initial logical qubit is in qubit 0
# Prepare the ancilla qubits
qc.h(0)
qc.h(1)
qc.h(2)
# Encoding using CNOT gates
qc.cx(0, 3)
qc.cx(1, 3)
qc.cx(1, 4)
qc.cx(2, 4)
qc.cx(0, 5)
qc.cx(2, 5)
qc.cx(0, 6)
qc.cx(1, 6)
qc.cx(2, 6)
# Introduce an error on qubit 3 (e.g., a bit-flip error)
qc.x(3)
# Decoding step (inverse of encoding)
qc.cx(0, 6)
qc.cx(1, 6)
qc.cx(2, 6)
qc.cx(0, 5)
qc.cx(2, 5)
qc.cx(1, 4)
qc.cx(2, 4)
qc.cx(0, 3)
qc.cx(1, 3)
qc.h(0)
qc.h(1)
qc.h(2)
# Measure all qubits
qc.measure(range(7), range(7))
```'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"}]}\''