Robust Certification of Entanglement Structures in Noisy Quantum Systems: Device‐Independent and Semi‐Device‐Independent Approaches

Abstract In the noisy intermediate‐scale quantum (NISQ) era, multipartite entanglement in realistic noisy environments exhibits complex structures. Characterizing entanglement structures—particularly entanglement depth and intactness—has become increasingly essential for quantum information processing tasks. Traditional methods like standard entanglement witnesses assume that experimenters can exactly implement specific quantum measurements. Even minor inaccuracies in standard witness can introduce significant errors in entanglement detection. Certification methods are proposed with relaxed assumptions about the system and measurements for entanglement structures. First, entanglement states are classified with the same intactness into three distinct types based on their depth. Next, analytical witnesses are derived to detect the entanglement structure of general n‐qubit systems in both device‐independent and semi‐device‐independent scenarios, where some observables are untrusted while others remain reliable. Furthermore, this framework is extended to account for small measurement imperfections, ensuring robustness in practical settings. It is demonstrated that this witness can detect larger entanglement regions compared to previous Bell‐type inequalities. Remarkably, for Type I 4‐partite quantum states, this entanglement witness with measurement imperfections is identical to both device‐dependent and semi‐device‐independent approaches.