# A Simple Quantum Algorithm to Create Tamper-Proof Digital Media

Simple — until you start implementing it!

Quantum Computer?

We can explore the conceptual use of quantum properties to detect tampering. The Hadamard gate can be used to put qubits into a superposition of states, which can be sensitive to tampering.

Here’s a conceptual algorithm using one Hadamard gate and two qubits to create a tamper-evident system for a digital file:

**Initialization:**

- Start with ten qubits all initialized to the |0⟩ state.

**2. Superposition:**

- Apply the Hadamard gate to each qubit to put them into a superposition of |0⟩ and |1⟩ states. Each qubit is now in the state (|0⟩ + |1⟩)/√2.

**3. Entanglement:**

- Use a series of CNOT gates to entangle the qubits with each other, creating a complex multi-qubit entangled state. This step is crucial because any tampering with a single qubit will affect the entire system due to entanglement.

**4. File Association:**

- Associate the state of these qubits with the digital file in a way that any attempt to access or tamper with the file would require interacting with the qubits. This could be a conceptual link where the qubits are part of a quantum system that controls access to the file.

**5. Tamper Detection:**

- Before any legitimate access to the file, measure the state of the qubits. Due to the nature of quantum mechanics, any tampering would have altered the entangled state, and the measurement outcomes would differ from the expected results if the system was tampered with.

**6. Verification:**

- Compare the measurement results with the expected outcomes. If the results match, the file has not been tampered with; if they do not match, the file integrity has been compromised.

**7. Access Control:**

- Allow access to the digital file only if the integrity check passes.

Here’s a simplified quantum algorithm for the process:

```
def initialize_qubits(num_qubits):
# Initialize qubits to |0⟩
for i in range(num_qubits)
qubits = [QuantumRegister(1, 'qubit{}'.format(i))]
return qubits
def apply_hadamard(qubits):
# Apply Hadamard gate to each qubit
for qubit in qubits:
circuit.h(qubit)
return circuit
def entangle_qubits(qubits):
# Entangle qubits using CNOT gates
for i in range(len(qubits) - 1):
circuit.cx(qubits[i], qubits[i + 1])
return circuit
def measure_qubits(circuit, qubits):
# Measure the qubits
for qubit in qubits:
circuit.measure(qubit, ClassicalRegister(1))
return circuit
def verify_integrity(measurements, expected_results):
# Verify if the measurements match the expected results
return measurements == expected_results
# Main algorithm
num_qubits = 10
qubits = initialize_qubits(num_qubits)
circuit = QuantumCircuit()
# Apply Hadamard gates to create superposition
circuit = apply_hadamard(qubits)
# Entangle the qubits
circuit = entangle_qubits(qubits)
# Expected results if no tampering has occurred
expected_results = calculate_expected_results(circuit)
# Before accessing the file, measure the qubits
measurements = measure_qubits(circuit, qubits)
# Verify the integrity of the file
if verify_integrity(measurements, expected_results):
print("File integrity verified. Proceed with access.")
else:
print("Tampering detected. Access denied.")
```

This pseudo-algorithm is a high-level representation and does not include the specifics of quantum circuit design, error correction, or the physical implementation of the quantum system.

In practice, the actual implementation would be much more complex and would require a real quantum computer to execute the quantum parts of the algorithm.