How to Build a Quantum Blockchain: Researchers Test a Blockchain That Only Quantum Computers Can Mine

Insider Brief

• Researchers at D-Wave have developed and tested a blockchain prototype that uses quantum computers to perform mining through a new consensus method called proof of quantum work.
• The system replaces energy-intensive classical mining with quantum computations that are infeasible for classical machines, achieving stable operation across four quantum processors.
• Experimental results show the blockchain maintained consensus and reached up to 75% mining efficiency, demonstrating a potential path toward scalable and energy-efficient blockchain infrastructure.

A team of D-Wave researchers has built and tested a blockchain that can only be mined using quantum computers, marking the first real-world application of quantum supremacy in blockchain technology.

The study, published on the pre-print server arXiv, outlines a prototype blockchain system that replaces the energy-intensive classical “proof of work” with a new consensus mechanism called “proof of quantum work.” The approach requires quantum computers to solve complex problems that classical machines cannot handle efficiently, making mining feasible only for quantum systems with current resources.

“We have proposed and successfully tested a blockchain architecture in which proof of quantum work (PoQ) is performed on quantum computers,” the authors write. “Our approach introduces multiple quantum-based hash generation methods, with varying levels of complexity depending on the capabilities of the quantum hardware. To address the inherent probabilistic nature of quantum hash generation and validation—an unavoidable property of any quantum hash algorithm—we developed techniques to ensure blockchain stability.”

Their prototype ran across four geographically distributed D-Wave quantum processors in North America, demonstrating that a blockchain powered entirely by quantum computation could function stably across hundreds of thousands of hashing operations.

A Shift in Blockchain Mining

Proof of work is a way to secure a blockchain by requiring computers to solve difficult puzzles before they can add new data. This makes it very hard for anyone to cheat, because doing so would require huge amounts of computing power and electricity.

It’s that last bit that is problematic. Traditional blockchains, particularly those like Bitcoin that use proof of work (PoW), have drawn widespread criticism because of their excessive use of energy. According to the study, Bitcoin mining alone is projected to consume nearly 176 terawatt-hours of electricity in 2024 — more than the annual electricity consumption of Sweden.

The researchers suggest that a proof of quantum work approach could change that. Quantum computation, though still expensive, consumes a fraction of the energy compared to PoW mining. The researchers estimate that energy use in their system amounts to just 0.1% of the cost of quantum computation, making PoQ potentially 1,000 times more energy efficient than classical mining, the researchers state.

The quantum blockchain also solves another key limitation of classical PoW: scalability. The quantum blockchain achieves higher mining efficiency and stable consensus, even under the uncertainty inherent in quantum computation.

The system integrates quantum operations into the standard blockchain framework with minimal changes to Bitcoin’s architecture.

How The Quantum Blockchain Works

Instead of miners racing to solve a brute-force cryptographic puzzle using high-powered GPUs or ASICs, this quantum blockchain uses quantum computers to generate a unique hash using probabilistic quantum mechanics. The process involves encoding data into a quantum system, allowing it to evolve, and then measuring properties of that system to produce a hash. These measurements are inherently probabilistic, requiring a mechanism to account for sampling errors and hardware noise.

To address the unreliability of quantum outcomes, the researchers introduced “probabilistic validation.” Both the miner and the validator use statistical confidence levels to assess whether a given quantum hash is valid. A new parameter, called “confidence-based Chainwork,” adjusts the perceived mining effort based on how trustworthy the quantum output appears to be.

This probabilistic consensus system also changes how the blockchain handles forks. Instead of invalid blocks being outright rejected, they are assigned negative work, allowing the chain to recover without network splits. This helps avoid a fatal failure mode where parts of the blockchain network become permanently disconnected due to inconsistent quantum outputs.

Experimental Results

The system was tested using four D-Wave Advantage quantum processors, each solving a complex problem rooted in quantum spin glass physics. These problems were chosen specifically because they are infeasible to solve using classical computers, ensuring that the quantum work being performed could not be faked or replicated.

Each quantum computer processed blocks using a fixed architecture, with miners adjusting “nonces” until they found a hash with a certain number of leading zeros—mirroring the mining process in Bitcoin. But in this system, only quantum computers could generate hashes that met the criteria.

In total, the blockchain ran over 100 miners and processed 219 block broadcasts. Over 70% of those blocks became immutable — agreed upon by all participants — demonstrating the system’s ability to reach consensus despite the randomness of quantum computation. Efficiency was measured by how many blocks joined the strongest chain. Chains using confidence-based validation showed significantly higher efficiency than those using simple binary validation.

Near-Term Quantum Application

The quantum blockchain presents a path forward for reducing the environmental cost of digital currencies. It also provides a practical incentive for deploying early quantum computers, even before they become fully fault-tolerant or scalable.

In this architecture, the cost of quantum computing — not electricity — becomes the bottleneck. That could shift mining centers away from regions with cheap energy and toward countries or institutions with advanced quantum computing infrastructure.

The researchers also argue that this architecture offers broader lessons. For example, unlike theoretical models that rely on quantum teleportation or fault-tolerant hardware, their blockchain runs on noisy intermediate-scale quantum (NISQ) devices available today.

“Beyond serving as a proof of concept for a meaningful application of quantum computing, this work highlights the potential for other near-term quantum computing applications using existing technology,” the researchers write.

Limitations and Future Work

The system is still a prototype, and hurdles remain before a quantum blockchain could be deployed commercially.

One of the major limitations, as mentioned, is cost. Quantum computing time remains expensive and limited in availability, even as energy use is reduced. At present, quantum PoQ may not be economically viable for large-scale deployment. As progress continues in quantum computing, those costs may be mitigated, the researchers suggest.

D-Wave machines also use quantum annealing — a different model from the quantum computing platforms pursued by companies like IBM and Google. Quantum annealers offer valuable capabilities for certain types of problems, though their use is currently more specialized compared to gate-based quantum systems.

There’s also the challenge of security. Classical blockchains rely on deterministic cryptographic hashes. The probabilistic nature of quantum hashes means that consensus must account for uncertainty. Although the researchers designed a system that adapts to this, it adds complexity and may require additional safeguards.

Looking forward, the researchers suggest integrating more sophisticated quantum features such as entanglement witnesses or shadow tomography to improve spoof resistance. They also propose using smaller, classically simulable problems to benchmark and calibrate QPUs.

ArXiv is a pre-print server, which means the work has not been officially peer reviewed. Researchers often use pre-prints to gain feedback on their work quickly, especially in fast-changing fields such as quantum computing. However, official peer-review research is the gold standard of the scientific method.

The research team included Mohammad H. Amin, Jack Raymond, Daniel Kinn, Firas Hamze, Kelsey Hamer, Joel Pasvolsky, William Bernoudy, Andrew D. King, and Samuel Kortas, all of D-Wave Quantum Inc.