The circuit prepares four qubits in different quantum states and then measures them in different bases.
```python
from qiskit import *
# Create a circuit with 4 qubits and 4 classical bits
qc = QuantumCircuit(4, 4)
# Alice's preparation
# Qubit 0: basis Z, bit 0 (do nothing)
# Qubit 1: basis X, bit 1 (apply X, then H)
qc.x(1)
qc.h(1)
# Qubit 2: basis Z, bit 1 (apply X)
qc.x(2)
# Qubit 3: basis X, bit 0 (apply H)
qc.h(3)
# Bob's measurement
# Qubit 0: measure in X basis (apply H)
qc.h(0)
qc.measure(0, 0)
# Qubit 1: measure in X basis (apply H)
qc.h(1)
qc.measure(1, 1)
# Qubit 2: measure in Z basis (direct measure)
qc.measure(2, 2)
# Qubit 3: measure in Z basis (direct measure)
qc.measure(3, 3)
```
'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"}]}\''