Entropy bounds for device-independent quantum key distribution with local Bell test
arxiv(2024)
摘要
One of the main challenges in device-independent quantum key distribution
(DIQKD) is achieving the required Bell violation over long distances, as the
channel losses result in low overall detection efficiencies. Recent works have
explored the concept of certifying nonlocal correlations over extended
distances through the use of a local Bell test. Here, an additional quantum
device is placed in close proximity to one party, using short-distance
correlations to verify nonlocal behavior at long distances. However, existing
works have either not resolved the question of DIQKD security against active
attackers in this setup, or used methods that do not yield tight bounds on the
keyrates. In this work, we introduce a general formulation of the key rate
computation task in this setup that can be combined with recently developed
methods for analyzing standard DIQKD. Using this method, we show that if the
short-distance devices exhibit sufficiently high detection efficiencies,
positive key rates can be achieved in the long-distance branch with lower
detection efficiencies as compared to standard DIQKD setups. This highlights
the potential for improved performance of DIQKD over extended distances in
scenarios where short-distance correlations are leveraged to validate quantum
correlations.
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