QCBRIEF
European Patent EP 4462727 covers Quantum B's Quantum Conference Key Agreement (QCKA): shared quantum states let independent nodes agree without a classical majority. The company's quantum key distribution (QKD) is emulated, not physical.
European Patent EP 4462727, granted to Quantum B (formerly Quantum Blockchains) by the European Patent Office this week, names a specific substitute for the trust assumption inside distributed consensus: a central quantum source emits a multi-particle Greenberger–Horne–Zeilinger (GHZ) state (a shared quantum state spread across several nodes), each node measures its particle, and the correlated outcomes let the network agree on shared data without a classical majority-vote round.
The mechanism, called Quantum Conference Key Agreement (QCKA), replaces two familiar trust models. In proof-of-work (the energy-intensive lottery behind Bitcoin-style networks), trust is paid for with computation and electricity. In classical majority-vote databases, trust rests on no party controlling more than half the nodes. QCKA substitutes a physical correlation: a central server sends time-bin encoded photons that become a shared multi-qubit state across the network, and the measurement results are correlated in a way the patent attributes to entanglement, not classical signaling.
The hardware story is separate. The company's pQKD platform, its emulated quantum key distribution offering, is not built on a physical quantum link. The Łódź and Lublin firm, led by CEO Mirek Sopek with co-inventor Miriam Kosik, participates in the EU-funded POSEIDON project on post-quantum digital identity, which is funding context, not a product claim.