On March 31, Google published a paper showing how a quantum computer could crack the cryptography protecting Bitcoin wallets. The paper’s authors estimate that their theorized quantum computer setup could derive someone’s private Bitcoin key from an exposed public key in about nine minutes. Bitcoin’s average block time — the time between exposing your public key and hiding it again — is ~10 minutes.

Quantum computers can hold superpositions — states that combine many possibilities at once, which can be manipulated to reveal answers a classical computer cannot (at least, not efficiently). When discovered by Richard Feynman in 1982, quantum computers were pitched as tools to solve physics problems; in 1994, mathematician Peter Shor discovered they could run an algorithm capable of cracking public-key cryptography.

Since the discovery of that algorithm (referred to in the industry simply as “Shor’s”), academics and national security hawks have been awaiting “Q-Day”: the arrival of a quantum computer that renders modern encryption irrelevant. Today, even if you recruited every single computer, data center, and loose electronic device in the world to work on the problem at the same time, recovering someone’s private key would take longer than 1 billion years. Quantum computers running Shor’s could do it in just minutes.

Quantum experts once believed breaking Bitcoin would require a computer with millions of qubits (a quantum computing version of a computer’s bit), well beyond what anybody could realistically build before 2040. Google’s paper changed that; its researchers estimate that a quantum computer would only need 500,000 qubits to run Shor’s for Bitcoin: 1/20th of experts’ previous estimate. Once that computer is built, millions of Bitcoin stored in early wallets that have their public keys exposed (including those that belong to Bitcoin’s anonymous founder, Satoshi), would be vulnerable. This would massively undermine the foundations of Bitcoin and crypto, and could trigger a chaotic forking scenario on or before Q-day.

We asked quantum and crypto experts what to make of it. Is the crypto world screwed? Or should you HODL till the heat death of the universe?

—Ryan Hassan