Curator's Take
This research tackles a fundamental challenge in quantum information processing: how to sequentially share quantum nonlocality among multiple observers when dealing with real-world noise. The work demonstrates that while certain types of quantum noise can completely destroy the ability to share nonlocality between successive observers, specific "noise-immune channels" can preserve this capability for arbitrarily many sequential measurements. What makes this particularly valuable is the development of adaptive measurement strategies that can actually switch which types of noise become immune, giving quantum systems more flexibility in noisy environments. This advances our understanding of how to design robust quantum communication protocols and device-independent quantum technologies that can function reliably despite the inevitable presence of environmental noise.
— Mark Eatherly
Summary
Sequential sharing of quantum nonlocality (SSQN) is crucial for device-independent tasks in quantum information processing, wherein relaying the post-measurement qubit through a local quantum channel to a subsequent observer constitutes an essential operational step. Here we present a theoretical analysis of noise robustness of sequential sharing for bipartite Bell nonlocality and tripartite Mermin nonlocality under the influence of local phase-flip, bit-flip, and depolarizing quantum channels. It is established that arbitrarily many independent observers can sequentially share the quantum nonlocality of Bell, Greenberger-Horne-Zeilinger, and W states via specific noise-immune channels, whereas this feature of SSQN is destroyed under other noisy quantum channels. Furthermore, we demonstrate that the noise-immune channel enabling unbounded SSQN can be switched by employing our newly designed measurement strategies assisted by local operations on the initial entangled states. Moreover, as illustrative examples, we propose two concrete schemes for sharing bipartite Bell nonlocality and tripartite Mermin nonlocality with two sequential local observers on one side subject to local noisy channels. Our work establishes a practical framework for realizing the SSQN under noisy quantum channels, and reveals the connection between noise robustness and measurement strategies.