The Jiuzhang quantum computer, developed by a team of Chinese researchers, made headlines in late 2020 for its claim to have achieved quantum computational supremacy. However, it is important to note that the term "quantum computational supremacy" refers to the ability of a quantum computer to solve a specific problem that is infeasible for classical computers, rather than its capability to break encryption algorithms.
Decrypting a Bitcoin wallet's private key using a quantum computer like Jiuzhang is currently considered beyond the reach of existing technology. Bitcoin and most cryptocurrencies rely on encryption algorithms that are considered secure against quantum attacks, primarily using elliptic curve cryptography (ECC).
Quantum computers have the potential to break certain asymmetric encryption algorithms, including ECC-based algorithms, using a quantum algorithm called Shor's algorithm. However, to decrypt a Bitcoin wallet's private key using Shor's algorithm, a quantum computer would require a sufficient number of error-corrected, stable qubits and the capability to run the algorithm successfully.
At present, quantum computers with the necessary number of qubits and error correction capabilities are not yet available. Estimates for when quantum computers with sufficient power to break ECC-based encryption exist range from several years to decades into the future.
To mitigate the potential threat of quantum attacks, efforts are already underway to develop post-quantum cryptographic algorithms (PQCs) that are resistant to attacks from both classical and quantum computers. These PQCs are being designed to replace current cryptographic algorithms and ensure the long-term security of digital systems, including cryptocurrencies.
In summary, while the Jiuzhang quantum computer may have achieved computational supremacy for certain tasks, it does not imply an immediate ability to decrypt Bitcoin wallets or other secure systems. The development of quantum computers capable of breaking cryptographic algorithms used in cryptocurrencies remains a significant challenge, and it is crucial to continue monitoring advancements in both quantum computing and post-quantum cryptography to ensure the security of digital assets.