A new quantum cryptography-based Bitcoin standard has been proposed that could harden the popular cryptocurrency against the advent of full-fledged quantum computers. Bitcoin as it now exists involves traditional public key cryptography and thus could conceivably be hacked by a future quantum computer strong enough to break it. However, quantum cryptography, which is based not on difficult math problems but the fundamental laws of physics, is expected to be strong enough to withstand even quantum computer-powered attacks.
The proposal, dubbed “qBitcoin,” posits transmission of quantum cryptographic keys between a remitter and a receiver of the eponomous named cryptocurrency, qBitcoin. The system would use provably secure protocols such as the BB84 quantum key distribution scheme.
To exchange qBitcoin, then, requires that there be a transmission network in place that can send and receive bits of quantum information, qubits. And that is no mean feat, considering it typically involves preserving the polarization states of individual photons across thousands of kilometers. To date, there are five known quantum key distribution networks in the United States, Switzerland, Austria, and Japan. China is working on their own massive 2000-km link, as well. And a number of satellite-to-satellite and satellite-to-ground quantum key distribution networks are also being developed and prototyped.