Quantum B Wins European Patent for Quantum Key Agreement Protocol
Quantum B, formerly known as Quantum Blockchains, has announced that the European Patent Office has granted it a patent for its Quantum Conference Key Agreement protocol. This protocol aims to achieve consensus in distributed systems. The Polish company describes a design that uses quantum-entangled photon states to enable independent network nodes to agree on shared data.
Quantum B’s Patented Technology
According to a report by The Quantum Insider, the patent details a system that generates time-bin encoded photons and transforms them into time-bin GHZ states. A quantum server distributes qubits to nodes, which then receive measurement outcomes.
These nodes communicate with each other over the classical internet. Each node derives bit values from its local measurements and shares an additional value for the agreement step. A node processes a data block when its value aligns with the majority of values received from other nodes.
Third-party reports cite application number EP23461579 and granted number EP 4462727. Miriam Kosik is a co-inventor. The complete list of inventors and the assignee of record are not included in public summaries. Mirek Sopek, CEO of Quantum B, stated that the company’s research “has progressed well beyond the solutions described in the granted patent.”
What the Patent Does Not Confirm
While a granted patent signifies that a claim is sufficiently novel to be registered, it does not confirm that the protocol has been implemented, simulated, or demonstrated in a laboratory setting. Currently, no such evidence is publicly available. There are no peer-reviewed papers, independent cryptanalyses, standards references, or certifications to evaluate the security claims.
Furthermore, performance figures are unavailable. The summaries do not provide information on key rate, participant count, transmission distance, latency, or authentication method. The design combines quantum-derived correlations with classical internet communication, meaning it is not post-quantum cryptography in the NIST definition, nor is it a standard QKD link. Instead, it is a distinct key-agreement mechanism with an added consensus layer.
This distinction is essential. Key agreement allows parties to share secret bits, while consensus requires parties to agree on a consistent record, even if some do not trust each other. The described majority-vote step, by itself, does not provide formal consensus guarantees. Quantum B also operates a pQKD hardware platform and participates in the EU-funded POSEIDON project.
Other organizations are developing related technologies. Fujitsu has open-sourced a quantum application package, and Altera and Riverlane have partnered on error correction. However, a technical paper, a public protocol specification, implementation results, or a named deployment would be necessary for further validation.