Quantum Computing Forum

Posted: **Sat Aug 12, 2023 4:30 am**

Question - Program and create an automated oracle generator for the Bernstein-Vazirani algorithm that randomly generates the secret state. Can you determine the value by just running the circuit and reviewing the results?

Answer -

Here is an automated oracle generator for the Bernstein-Vazirani algorithm in Qiskit. The Bernstein-Vazirani algorithm efficiently determines the secret n-bit string of a given oracle, which is a black-box function. Let's create the automated oracle generator and then run the circuit to determine the secret value.

Code: Select all

from qiskit import QuantumCircuit, Aer, execute

# Define the number of qubits (n) for the secret state
n = 5

# Generate a random n-bit secret string
import random
secret_string = ''.join(random.choice(['0', '1']) for _ in range(n))

# Create a quantum circuit with n+1 qubits
circuit = QuantumCircuit(n+1, n)

# Apply Hadamard gates to all qubits
circuit.h(range(n))

# Apply the oracle for the secret string
for i, bit in enumerate(secret_string):
    if bit == '1':
        circuit.cx(i, n)

# Apply Hadamard gates again to the input qubits
circuit.h(range(n))

# Measure the input qubits
circuit.measure(range(n), range(n))

# Simulate the circuit
simulator = Aer.get_backend('qasm_simulator')
job = execute(circuit, simulator, shots=1)

# Get and print the measurement result
result = job.result().get_counts()
print("Measured Result:", result)
print("Secret String:", secret_string)

This code generates a random n-bit secret string, constructs the quantum circuit for the Bernstein-Vazirani algorithm, simulates the circuit, and prints the measurement result along with the secret string.

When you run the circuit and review the results, you should observe that the measured result matches the secret string. This demonstrates the power of the Bernstein-Vazirani algorithm in efficiently determining the secret value of a black-box function.

Note that while the Bernstein-Vazirani algorithm can efficiently determine the secret string in a single run, this might not be the case for all oracles or quantum algorithms. In some cases, you might need to repeat the experiment multiple times to increase the confidence in the obtained result, especially when dealing with real quantum hardware where noise and errors can affect the outcomes.