Google has released a paper laying out a theoretical scenario in which a quantum computer could derive a Bitcoin private key in nine minutes. On April 5, CoinDesk reported that the idea could spread beyond Bitcoin to other tokens such as Ethereum, and further into cryptographic systems across private finance.

The discussion starts from the point that quantum computers are easily misunderstood as simply “faster computers.” They are not stronger chips or bigger server farms, but “a fundamentally different kind of machine at the atomic level.” While classical computers process information using bits that hold either 0 or 1, quantum computers use qubits. The key is that a qubit can be 0, 1, or both at the same time.

A leading implementation method used by Google is a structure that cools a tiny ring of superconducting metal to extremely low temperatures. In an environment close to absolute zero, electric current flows without resistance and maintains a quantum state. In the ring, current can flow clockwise (0) or counterclockwise (1), but at the quantum scale it can also flow in both directions at the same time in a “superposition.” The article stresses that this should not be understood as “switching very quickly between the two,” and that the current exists in both states at once in a measurable, experimentally verifiable way.

The problem is that this state is extremely fragile. When it interacts with external factors such as air molecules, heat, vibration and light, superposition collapses through decoherence. That is why Google’s equipment operates inside a “large room-sized” dilution refrigerator and shielding. Even so, qubits often lose their quantum state, making error correction a central task in discussions about scaling.

Quantum computers are cited as particularly threatening in cryptography. Bitcoin security relies on an asymmetry: it is fast to compute a public key from a private key, but reversing from a public key to a private key would take a classical computer a million years, even “longer than the age of the universe.” Quantum computers, the article says, can traverse this trapdoor in reverse using Shor’s algorithm. The paper suggests the resources required could be far lower than previous estimates, and assumes it could be possible on a time frame that can compete with Bitcoin’s block finality time.

The discussion does not mean Bitcoin’s cryptographic system is immediately neutralised. It is closer to a warning that response strategies should be accelerated in line with the pace of quantum-technology development. The assessment is that not only major blockchain networks including Bitcoin and Ethereum, but also the broader private financial sector, can no longer postpone the shift to quantum-resistant cryptography as merely a theoretical task.