Arbitrarily Loss-Tolerant Quantum Position Verification in a Single Execution

Quantum position verification (QPV) seeks to certify the spatial location of an untrusted prover, but is challenged fundamentally by entanglement-based attacks and experimentally by photon loss. Both issues were addressed separately in different works and were simultaneously resolved for sequentially repeated protocols in Phys.\ Rev.\ Lett.\ 135, 260801 via a commitment-based modification that renders security independent of transmission losses. However, single-execution protocols are preferable in practice, and the original techniques do not extend to the parallel setting due to their reliance on sequential structure. We overcome this by utilizing different techniques based on no-signalling correlations, lifting the commitment modification to the parallel regime while preserving the security guarantees of the underlying QPV protocol. Applying this to a BB84-based QPV protocol suitable for near-term implementation and secure against bounded-entanglement adversaries, we prove that fixing a threshold k on the number of successfully committed qubits yields an adversarial acceptance probability that decays exponentially in k. The resulting protocol maintains robustness to noise levels of up to 3.7\% and remains secure under arbitrarily slow quantum communication, as does the original protocol. This yields the first fully loss-tolerant single-shot QPV protocol secure against entangled attackers, making QPV feasible over arbitrary distances. Finally, we refine the sequential analysis and obtain improved quantitative parameters for experimental implementations.