Juan Carlos Giraldo Vidal

We study the problem of verifying quantum states in restricted-access quantum devices, as commonly encountered in cloud-based quantum computing. In such scenarios, users interact with hardware through limited interfaces, motivating verification approaches that rely only on observed statistics, in the spirit of device-independent and semi-device-independent frameworks. We introduce a black-box model in which the device is treated as an oracle with constrained input-output capabilities. Within this setting, we define a simple and implementation-agnostic statistical test for the certification of bipartite entangled states, specifically Bell states, based solely on measurement outcomes. The test is formulated as a hypothesis test using an error parameter analogous to the Quantum Bit Error Rate (QBER). Our main contribution is the introduction of this test together with its experimental validation under realistic access constraints. We implement the proposed method on a 2-qubit NMR platform and observe a stable baseline error rate of approximately 9%, which we interpret as an empirical noise floor. This value naturally defines a tolerance threshold for detecting statistically significant deviations from ideal behavior. Our results provide a concrete instance of semi-device-independent verification and suggest that noise profiles can be leveraged as practical certification tools in access-constrained quantum systems.