Artur Ekert’s 1991 E91 protocol turns entangled photon pairs and a Bell test into a shared secret key. This guide covers how it works, how it compares with BB84 and BBM92, and what experiments from Micius to 100 km device-independent QKD have shown.
Month: October 2026
Which Bitcoin Addresses Are Vulnerable to Quantum Computers?
Quantum computers threaten Bitcoin addresses whose public keys are visible on-chain, not the blockchain itself. This guide ranks P2PK, reused, Taproot and unspent hashed addresses by exposure and explains what you can do now.
Can Quantum Computers Break Ethereum? Risks, Qubits and the 2029 Plan
No quantum computer can break Ethereum today, but its elliptic-curve signatures have a known weakness and Google’s 2026 estimates moved the goalposts. Here is what is exposed, how many qubits an attack needs, and how Ethereum plans to be post-quantum by 2029.
EPR Paradox Explained: From Einstein’s 1935 Doubt to the 2022 Nobel
In 1935 Einstein, Podolsky and Rosen argued that quantum mechanics must be incomplete. This guide covers their argument, the replies, Bell’s theorem, the 2015 loophole-free Bell test, the 2022 Nobel Prize and why entanglement cannot carry messages.
Quantum Internet Explained: Repeaters, Teleportation, Real Links
A quantum internet distributes entanglement between distant nodes. It is not a faster internet. Here is how repeaters, teleportation and deployed-fiber links actually work, what has been demonstrated by 2026, and why it does not replace post-quantum cryptography.
BB84 Protocol Explained: How QKD Works and Where It Breaks
A step-by-step guide to the BB84 protocol: how two parties agree on a secret key with photons, why an eavesdropper leaves a 25% error rate, and which assumptions real systems have failed to meet.
NSA Still Won’t Back Quantum Key Distribution: The 2026 Rewrite
The NSA’s October 2026 rewrite of its QKD guidance keeps the 2020 verdict: no quantum key distribution for National Security Systems for now. Here is what stayed the same, what is new, and what it means for anyone choosing between QKD and post-quantum cryptography.
Is RSA Deprecated in 2030? NIST IR 8547’s Deadlines Explained
RSA does not stop working in 2030. NIST IR 8547 proposes deprecating 112-bit RSA after 2030 and disallowing all quantum-vulnerable public-key algorithms after 2035. Here is what that means and which deadlines may reach you sooner.
Magic State Cultivation: What Google’s 40x Willow Result Means
Google reports that magic state cultivation cut errors 40x on its Willow processor. Here is what magic states are, why the T gate is a bottleneck, and what the result does and does not mean for RSA, ECDSA and crypto wallets.
Can Quantum Computers Break SHA-256? What Grover and BHT Really Do
Quantum computers weaken SHA-256 in a predictable, bounded way: about 128 bits of preimage security remain, and real hardware costs are far higher than the query counts suggest. Here is what Grover’s and BHT’s algorithms actually do.