The notion that quantum computers pose an imminent threat to bitcoin's security has been a subject of intense speculation. However, recent studies suggest that the actual threat is more nuanced. Two key aspects of bitcoin's security are under scrutiny: wallet security, which could be compromised by a sufficiently powerful quantum computer, and mining, where quantum computers could potentially speed up the process.
Nevertheless, the energy required to launch such an attack is staggering, estimated to be on the order of a star's energy output. This is due to the vast number of delicate operations required, each necessitating a dedicated support system of thousands of qubits to keep errors in check. Furthermore, the production of new blocks every ten minutes means an attacker would have a narrow window to complete the task, necessitating an enormous number of machines running in parallel. The estimated 10²³ qubits and 10²⁵ watts needed are far beyond current technological capabilities, making a quantum 51% attack physically unfeasible.
Another area of concern is the replication of major quantum factoring breakthroughs, which researchers have managed to achieve using outdated hardware, such as a 1981 VIC-20 home computer, and even a dog, highlighting the simplicity of the problems being solved. The real vulnerability lies in bitcoin wallets, particularly those with exposed key information on the blockchain, which could be targeted if quantum machines advance.
Recent research suggests that the computing power required for such an attack could decrease significantly, but building the necessary machine remains physically impossible with current technology. Developers are working on fixes, including reducing key exposure and creating quantum-resistant signatures. While the quantum threat to Bitcoin is real, it is essential to understand that the development of machines capable of launching such attacks is hindered by physical constraints.