The Protocol

1. Alice sends qubits in random bases (⊕ or ⊗)
2. Bob measures in random bases
3. They publicly compare bases (not values)
4. Keep only matching-basis measurements
5. Check error rate to detect eavesdroppers

Why It's Secure

• • No-cloning theorem prevents copying qubits
• • Measurement disturbs quantum states
• • Eavesdropping introduces detectable errors
• • Error rate >11% indicates interception