A paper published by BTQ Technologies calculates that using quantum computers to mine bitcoin at current difficulty would demand roughly 10 to the power of 25 watts — approaching stellar energy output — and argues the real quantum threat lies in cryptographic signatures, not mining.
A new academic paper has put hard numbers on the fantasy of quantum bitcoin mining — and the figures are, quite literally, astronomical.
Pierre-Luc Dallaire-Demers, a researcher at BTQ Technologies, published "Kardashev Scale Quantum Computing for Bitcoin Mining" on arXiv this week, delivering what appears to be the first end-to-end physical cost estimate for deploying quantum hardware against Bitcoin's proof-of-work algorithm. The conclusion: even under the most generous assumptions about future quantum hardware, competitive mining would require resources that make the exercise physically absurd.
The paper's title references the Kardashev Scale — a theoretical framework devised by Soviet astronomer Nikolai Kardashev in 1964 to classify civilisations by their total energy consumption. A Type I civilisation harnesses all energy available on its home planet; a Type II captures the full output of its star. The point of invoking it here is not rhetorical flourish. It's the scale at which quantum mining actually operates.
In the most favourable scenario the paper models — a partial-preimage attack against a simplified version of Bitcoin's hash function — a quantum miner would need roughly 10 to the power of 8 physical qubits and 10 to the power of 4 megawatts of power. That's already equivalent to a large national electricity grid dedicated to a single mining operation. At Bitcoin's actual mainnet difficulty, measured in January 2025, the requirements explode to approximately 10 to the power of 23 qubits and 10 to the power of 25 watts — a figure that approaches the luminosity of a mid-sized star.
"To push mining into non-trivial consensus effects, one must invoke astronomical quantum fleets operating at energy scales that lie far above present-day civilisation," Dallaire-Demers writes.
The underlying problem is Grover's algorithm, which provides a theoretical quadratic speedup for unstructured search problems — the kind of brute-force computation that underpins proof-of-work mining. In textbook form, that speedup sounds threatening. In practice, it collapses. The paper demonstrates that once you factor in the physical overhead of quantum error correction, the construction of the oracle circuits needed to evaluate SHA-256 hashes, and the logistics of running parallel quantum machines within Bitcoin's ten-minute block interval, the advantage evaporates entirely.
Bitcoin's difficulty adjustment is the critical constraint. The network recalibrates every 2,016 blocks to maintain a roughly ten-minute interval between blocks, which limits how much benefit a faster search algorithm can extract. A quantum attacker can't simply wait longer for a better result; they must compete within the same time window as every classical miner on the network. That forces parallelism — and parallel quantum machines multiply both hardware and energy costs linearly.
The paper's real contribution, however, may be in redirecting attention toward a threat it considers genuinely urgent. Public discussion of quantum risks to Bitcoin frequently conflates two very different problems: attacks on mining via Grover's algorithm, and attacks on Bitcoin's elliptic-curve digital signatures via Shor's algorithm. The latter — which could theoretically allow an attacker to derive private keys from public keys and steal funds — is a credible near-term concern that the Nobel physicist John Martinis warned about last week.
BTQ Technologies, a Nasdaq-listed quantum technology firm, has a commercial interest in the distinction; the company is developing Bitcoin Quantum, a post-quantum Bitcoin architecture designed around cryptographic primitives resistant to Shor's algorithm. But the paper's physics hold regardless of the company's product roadmap. The energy calculations rely on well-established models of superconducting qubit error rates and refrigeration costs, not speculative hardware improvements.
The practical takeaway for the Bitcoin community is straightforward. Mining is not the vulnerability. Signatures are. Circle's forthcoming Arc blockchain has already adopted quantum-resistant cryptography, and the pressure on Bitcoin's core developers to implement similar protections will only intensify as quantum hardware matures. The energy of a star is safe from Grover's algorithm. Private keys are not safe from Shor's.
