Google's Willow chip cuts quantum errors 40-fold, raising stakes for old Bitcoin wallets
Google shrinks a key quantum computing error hurdle
Google says its Willow quantum chip has reduced errors about 40-fold when preparing special quantum states needed for advanced calculations. The work, published in the journal Science this week, tackles one of the costly hardware steps toward building machines powerful enough to crack Bitcoin wallets.
Quantum computers use particles called qubits. Google's result focused on "magic states" — special setups that quantum computers must prepare in large numbers to run powerful algorithms. Getting these states right without errors has been a major bottleneck.
The numbers behind the breakthrough
Among the magic states that passed inspection, about 99.99 percent were accurate. But only about 8 percent of all preparation attempts succeeded. Researchers note that substantial scaling challenges remain before such error reduction can be used in a real attack.
Under one modeled Bitcoin attack, a quantum machine would need to sustain roughly 500,000 reliable magic states per second. Google's findings advance an engineering method that could help reach that goal, but the company does not claim a practical attack is now closer.
Why the oldest Bitcoin matters
Bitcoin wallets rely on a secret key to approve payments and a matching public key that lets the network verify those approvals. Some payment types reveal the public key right away. In theory, a large enough quantum computer running Shor's algorithm could reverse the math from the public key back to the secret key. Whoever recovered the secret could then sign transactions as the wallet owner.
Some older Bitcoin payment formats hide the public key behind a hash until the owner spends. That gives a potential attacker less time to act. But many of Bitcoin's oldest holdings — mined in the earliest years of the network — have had their public keys exposed since they were created.
Old wallets are moving
Some of Bitcoin's oldest holdings have started moving as the quantum debate grows louder. On Oct. 7, 100.02 BTC untouched since July 2010 moved after more than 16 years, carrying a value of about $8.5 million. In August, six wallets inactive since 2011 to 2014 moved another 553.59 BTC, worth roughly $40 million at the time.
The article notes these transfers do not singularly prove holders are responding to quantum fears, as movement can have other causes.
What the source says
The CoinDesk article treats the results as a meaningful engineering advance rather than an immediate threat. It emphasizes that the experiment did not make a Bitcoin attack 40 times cheaper and that far more work is needed before any quantum computer could attempt to recover a Bitcoin secret key from a public key.
What remains unclear
It is still unclear how long it will take to scale quantum hardware to the level needed for a Bitcoin attack. The gap between preparing a handful of high-quality magic states in a lab and sustaining hundreds of thousands per second on a usable machine remains very large. No one has yet demonstrated Shor's algorithm on a cryptographically relevant key size.
Why this matters for Bitcoin
If quantum computers ever reach the required scale, Bitcoin's oldest coins would be the most exposed because their public keys are already visible on the blockchain. Bitcoin can introduce stronger spending protections, but someone would still need the existing secret keys to move old holdings into new formats. If those keys are lost, the owner cannot make the move, and the exposed public key remains available to a future attacker.
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