On December 10, 2024, Google announced the launch of its latest quantum computing chip — Willow.
The chip has 105 quantum bits (qubit) and has achieved best-in-class performance in quantum error correction and random circuit sampling.
Technological breakthroughs of the Willow chip.
The Willow chip excelled in RCS benchmark tests, completing a standard computation in less than 5 minutes, while this computation would take over 10²⁵ years for the fastest supercomputers to complete.
Hartmut Neven, head of quantum artificial intelligence, pointed out that this timeframe exceeds the known timescale of physics, far surpassing the age of the universe.
Google CEO Sundar Pichai stated that Willow is an important step for the tech giant to build a 'useful quantum computer' and is expected to have practical applications in fields such as drug discovery, fusion energy, and battery design.
The potential threat of quantum computing to Bitcoin.
As quantum computing technology advances, concerns about its potential threat to Bitcoin's security have resurfaced in the community.
Bitcoin relies on Elliptic Curve Digital Signature Algorithm (ECDSA) and SHA-256 hash algorithm to ensure network security.
In theory, quantum computing could use Shor's algorithm to break ECDSA and thus obtain private keys; breaking SHA-256 would require Grover's algorithm, which needs hundreds of millions of quantum bits.
Bitcoin entrepreneur Ben Sigman pointed out that breaking ECDSA requires millions of physical quantum bits, and the requirements for breaking SHA-256 are even higher, indicating that current quantum computing technology does not pose a direct threat to Bitcoin.
Satoshi Nakamoto's Bitcoin design and the response to quantum computing.
The design of Bitcoin is adaptive, capable of responding to potential computational threats.
Sigman explained that if a quantum computer could calculate SHA-256 faster than the current global mining hash power (750 exahash), and assuming it could mine one block per minute, it would mine 6,300 bitcoins in just 33 hours.
Subsequently, the mining difficulty would be adjusted back to the 10-minute target, reducing the mining efficiency of the quantum computer.
Former Google senior product manager Kevin Rose also pointed out that breaking Bitcoin's encryption algorithm would require a quantum computer with about 13 million quantum bits, while the number of quantum bits in the Willow chip is far from sufficient.
The future of quantum computing and the security of Bitcoin.
Emin Gün Sirer, founder of Avalanche, further explained that although the progress of quantum computing is impressive, it currently does not pose a threat to the security of crypto assets. Quantum computing will make some operations (like factoring) easier, but others (like reversing one-way hash functions) remain equally difficult. Additionally, the attack window for quantum computers is relatively small, making the work of quantum attackers more complex.
However, Sirer also warned that there is a more pressing issue regarding the 1.1 million bitcoins that Satoshi Nakamoto is estimated to hold. The bitcoins mined by Nakamoto in the early days used a very old payment-to-public-key (P2PK) format, which could leak the public key, giving attackers time to mine.
Therefore, as the threat of quantum computing increases, the Bitcoin community may need to consider freezing Satoshi Nakamoto's coins, or more broadly, providing a sunset date to freeze all coins in P2PK UTXO.
Conclusion
Satoshi Nakamoto foresaw this issue and proposed a solution. He believed that if SHA-256 were to be broken, one could restart with a 'honest blockchain' to reach consensus, locking its state and continuing with a new hash function.
This flexible design allows Bitcoin to adapt to potential technological challenges in the future.