A live governance fight is playing out in the Bitcoin community over how — and whether — to defend the network against future quantum computers. A proposal called BIP-361 would eventually freeze coins in wallets that don't upgrade to quantum-resistant addresses, and it has split developers, miners and prominent holders including Strategy's Michael Saylor. Here's what the debate is actually about, how real the quantum threat is today, and what it means for anyone holding Bitcoin. Bitcoin's security relies on elliptic-curve cryptography (ECDSA), which today's computers cannot break in any practical timeframe. The concern is that a sufficiently powerful quantum computer — a machine that uses quantum mechanics rather than classical bits to perform certain calculations far faster — could one day derive a private key from a public one, potentially exposing coins held in older address types. In March 2026, Google's Quantum AI team published research suggesting elliptic-curve cryptography could be broken with fewer resources than previously thought — as low as roughly 1,200-1,450 logical qubits, rather than earlier estimates in the tens of millions of physical qubits (CoinDesk, The Protocol, 1 April 2026). But Google's own Willow chip has only around 105 qubits, and a company spokesperson said plainly that “the Willow chip is incapable of breaking modern cryptography” (Cryptopolitan). Google has set 2029 as its own internal target for migrating its authentication services to post-quantum cryptography — a planning deadline, not a claim that a Bitcoin-cracking machine will exist by then (CryptoRank.io). A Google-commissioned study estimated around 6.9 million BTC currently sit in address types that would be vulnerable if a cryptographically relevant quantum computer existed today. Estimates for when such a machine might exist vary widely: IBM targets 200 logical qubits by 2029 with its Starling system, while Blockstream chief executive Adam Back has argued the