Scientists propose quantum proof-of-work consensus for blockchain

Boson sampling was once considered a problem looking for a solution. Now, it might be the bridge that brings quantum computing to the blockchain.

A team of researchers from universities in Australia and the United States, working in collaboration with quantum technology company BTQ, recently published research proposing a novel proof-of-work (PoW) scheme for blockchain consensus that relies on quantum computing techniques to validate consensus.

Our new paper on using NISQ-era quantum sampling problems in proof-of-work blockchain consensus algorithms. In collaboration with @BTQ_Tech.https://t.co/MKAB2czqSk

— Peter Rohde (@drpeterrohde) June 1, 2023

Dubbed “Proof-of-work consensus by quantum sampling,” the preprint research paper details a system that the authors claim “provides dramatic speedup and energy savings relative to computation by classical hardware.”

According to the researchers, current algorithms for solving PoW consensus puzzles are slow and require a significant amount of computation resources to process:

“Whereas classical PoW schemes such as Bitcoin’s are notoriously energy inefficient, our boson sampling-based PoW scheme offers a far more energy efficient alternative when implemented on quantum hardware.”

According to the paper, the quantum advantage provided by this scheme would also increase the difficulty of mining, thus making it possible to “maintain consistent block mining time” as the number of miners increases, further incentivizing continuing participation of “quantum miners.”

The sampling process the researchers refer to, boson sampling, isn’t a new one, but its application to blockchain technology appears novel. Boson sampling has shown promise in numerous quantum computing applications. Still, as a non-universal quantum computing solution (it has to be used in a system built for a specific task), its potential has been limited to a select few domains, such as chemistry.

Related: How does quantum computing impact the finance industry?

However, according to the researchers, it may be the perfect solution for future-proofing blockchain applications and, potentially, lowering the environmental impact of mining on the Bitcoin blockchain and similar chains.

Aside from quantum advantage, quantum hardware also has a leg up on old school computers due to the nature of how blockchain mining works.

One of the current advantages of classical supercomputers over their new quantum cousins is the ability to “precompute” when handling the same class of problem regularly. But, when it comes to blockchain, such precompute is essentially wasted.

Mining is, as the researchers put it, a problem that is “progress-free.” No matter how many times a blockchain puzzle is solved to provide proof-of-work, the computer and algorithms processing the challenges don’t ever get any better at solving the problem.

This means that quantum computers, despite being notoriously challenging to develop and expensive to build and maintain, would ultimately be capable of validating consensus more efficiently than state-of-the-art classical systems.