This circuit implements Simon's Algorithm for a secret string '11', identifying that two inputs produce the same output if they are bit-wise XOR is '11'.
```python
from qiskit import *
# Simon's Algorithm Implementation with 4 qubits and 2 classical bits
qc = QuantumCircuit(4, 2)
# Apply Hadamard gates to the first two qubits (input register)
qc.h([0, 1])
# Oracle for the secret string s = '11'
# Implementing f(x) = f(y) iff x ⊕ y = s
qc.barrier()
# Apply CNOT gates representing the oracle function
qc.cx(0, 2)
qc.cx(1, 2)
qc.cx(0, 3)
qc.cx(1, 3)
qc.barrier()
# Apply Hadamard gates to the first two qubits again
qc.h([0, 1])
# Measure the first two qubits
qc.measure([0, 1], [0, 1])
```
{
"00": 474,
"01": 47,
"10": 39,
"11": 464
}