Abstract
The violation of a Bell inequality is the paradigmatic example of device-independent quantum information: The nonclassicality of the data is certified without the knowledge of the functioning of devices. In practice, however, all Bell experiments rely on the precise understanding of the underlying physical mechanisms. Given that, it is natural to ask: Can one witness nonclassical behavior in a truly black-box scenario? Here, we propose and implement, computationally and experimentally, a solution to this ab initio task. It exploits a robust automated optimization approach based on the stochastic Nelder-Mead algorithm. Treating preparation and measurement devices as black boxes, and relying on the observed statistics only, our adaptive protocol approaches the optimal Bell inequality violation after a limited number of iterations for a variety photonic states, measurement responses, and Bell scenarios. In particular, we exploit it for randomness certification from unknown states and measurements. Our results demonstrate the power of automated algorithms, opening a venue for the experimental implementation of device-independent quantum technologies.
Highlights
The paradigmatic example of device independence is the violation of a Bell inequality [2]
It provides the most radical departure of quantum theory from classical concepts and paves the way for applications ranging from cryptography [3], randomness certification [4], self-testing [5], and communication complexity [6,7]
The violation of a Bell inequality is often pictured as the paradigmatic example of a device-independent task: From the observed statistic alone, without knowing the internal working of devices, one can conclude the nonclassical nature of it
Summary
The experimental guidance is quintessential in science. Empirical evidence is crucial to the development of models and allows one to test and improve theories. The paradigmatic example of device independence is the violation of a Bell inequality [2] It provides the most radical departure of quantum theory from classical concepts and paves the way for applications ranging from cryptography [3], randomness certification [4], self-testing [5], and communication complexity [6,7]. We propose an adaptive automated optimization protocol exactly to solve this ab initio task, in particular, focusing on optimizing the violation of Bell inequalities without any prior knowledge of the quantum system and measurements—that is, in a fully black-box scenario. After a few hundreds of measurements the algorithm is able to approach the maximum possible violation for a given entangled state In this way, we take a step forward for the crucial task of testing automated protocols in experimental noisy scenarios. We exploit it for maximizing the certified randomness extraction from an unknown system and unknown measurements, opening a fruitful venue for the device-independent quantum information framework
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
