Create grover.py

projects/pi-nexus-iam/quantum-computing/qc-algorithms/grover.py

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+import numpy as np
+from qiskit import QuantumCircuit, execute, Aer
+
+def grover_oracle(f, n: int) -> QuantumCircuit:
+    """
+    Creates a Grover oracle circuit for the function f.
+
+    Args:
+    f: The function to be searched.
+    n: The number of qubits.
+
+    Returns:
+    The Grover oracle circuit.
+    """
+    qc = QuantumCircuit(n + 1)
+
+    # Apply the function f
+    for i in range(n):
+        if f(i):
+            qc.x(n)
+
+    # Apply the diffusion operator
+    qc.h(range(n))
+    qc.x(range(n))
+    qc.h(range(n))
+
+    return qc
+
+def grover_search(f, n: int) -> int:
+    """
+    Grover's algorithm for searching an unsorted database.
+
+    Args:
+    f: The function to be searched.
+    n: The number of qubits.
+
+    Returns:
+    The index of the marked element.
+    """
+    qc = QuantumCircuit(n + 1)
+
+    # Initialize the qubits
+    qc.h(range(n))
+
+    # Apply the Grover oracle
+    for _ in range(int(np.pi / 4) * np.sqrt(2 ** n)):
+        qc.compose(grover_oracle(f, n), inplace=True)
+
+    # Measure the qubits
+    qc.measure(range(n), range(n))
+
+    # Run the circuit on a simulator
+    simulator = Aer.get_backend('qasm_simulator')
+    job = execute(qc, simulator, shots=1024)
+    result = job.result()
+
+    # Extract the index from the measurement results
+    index = 0
+    for i, count in enumerate(result.get_counts().items()):
+        if count[1] > 100:
+            index = i
+            break
+
+    return index
+
+# Example usage
+def f(x: int) -> bool:
+    return x == 5
+
+n = 6
+index = grover_search(f, n)
+print(f"Index of the marked element: {index}")