Sequential device-independent certification of indefinite causal order

Indefinite causal order has found numerous applications in quantum computation, communication, and metrology. Before its usage, the quality of indefinite needs to be first certified, certification should ideally device-independent (DI) avoid impact device imperfections. In this work, we initiate study sequential DI an order. This can useful experimental platforms where generation is difficult. We show that arbitrary number certifications achieved with a switch also analyze practical requirements for implementations certifications. Our work opens possibility reusing resource multiple times information processing.