2025 · UNC Chapel Hill

Quantum Cryptography

Aug – Dec 2025Quantum mechanics capstone

How do you share a secret when someone might be listening? I analyzed the BB84 and E91 quantum key distribution protocols, in which physics itself exposes the eavesdropper, and delivered a public talk with a live demonstration.

The protocols

BB84 encodes bits in conjugate photon bases, so any measurement by an eavesdropper leaves fingerprints in the error rate. E91 goes further and builds the key from entangled pairs, using a Bell test as the security guarantee. I worked through both, including the practical attacks that separate the ideal protocol from real hardware.

The talk

The result was a paper and a public talk with a live demonstration of quantum key exchange, built to make a genuinely strange piece of physics land with a general audience.

Read the paper full screen (PDF)

Some slides have animations that only play in the live deck. Open it in slideshow mode to see them.

Open the live deck
Quantum informationBB84E91Entanglement