Find the value recognized by the oracle in sqrt(N) attempts.

def make_grover_circuit(input_qubits, output_qubit, oracle):
    """Find the value recognized by the oracle in sqrt(N) attempts."""
    # For 2 input qubits, that means using Grover operator only once.
    c = cirq.Circuit()

    # Initialize qubits.
    c.append([
        cirq.X(output_qubit),
        cirq.H(output_qubit),
        cirq.H.on_each(*input_qubits),
    ])

    # Query oracle.
    c.append(oracle)

    # Construct Grover operator.
    c.append(cirq.H.on_each(*input_qubits))
    c.append(cirq.X.on_each(*input_qubits))
    c.append(cirq.H.on(input_qubits[1]))
    c.append(cirq.CNOT(input_qubits[0], input_qubits[1]))
    c.append(cirq.H.on(input_qubits[1]))
    c.append(cirq.X.on_each(*input_qubits))
    c.append(cirq.H.on_each(*input_qubits))

    # Measure the result.
    c.append(cirq.measure(*input_qubits, key='result'))

    return c