Structural explanation for trust-assignment asymmetry in one-sided DIQKD

Determine when and why extracting the secret key from the untrusted party improves the performance of one-sided device-independent quantum key distribution, and characterize the conditions under which this behavior arises.

Background

The numerical results show that the party whose measurement device is characterized need not always be the party from which the highest key rate is obtained. In particular, the one-sided CHSH protocol exhibits improved performance when the key is extracted from the untrusted side, contrary to the intuitive expectation that trusting the key-generating party should be advantageous. The paper identifies understanding the origin and scope of this reversal as an unresolved design question for one-sided DIQKD protocols.

References

Our results can therefore only provide a first exploration of this largely open design question.

— Computing key rates for one-sided device-independent quantum key distribution  (2608.25915 - Bluhm et al., 26 Aug 2026) in Section "Discussion and outlook"

Different assumptions remove different engineering requirements, and it is not clear whether the asymmetry found at the level of idealized key rates persists once losses, detector imperfections, calibration requirements, and implementation complexity are taken into account.

— Computing key rates for one-sided device-independent quantum key distribution  (2608.25915 - Bluhm et al., 26 Aug 2026) in Section "Discussion and outlook"