Observation of the State-Independent Contextuality under No-Signaling Conditions
Contextuality, the impossibility of assigning context-independent measurement outcomes, is a critical resource for quantum computation and communication. An essential requirement for any test of contextuality, namely, no-signaling between successive measurements should be accomplished, which is difficult to achieve in practical. Here, based on the graph-theoretic approach, we provide an optimal state-independent contextuality inequality for all quantum states in the simplest scenario with 13 elementary measurements, in which a larger deviation from the classical bound can be obtained. We then experimentally observed the violation of the inequality respecting the condition of no-signaling between the measurements in the same context, which is essential to make sense of any test of contextuality. Our experimental results agree with the quantum predictions and confirm the existence of contextual correlations between sequential compatible measurements which are independent of the initial state of the system. This work sheds a new light on the study of quantum contextuality under no-signaling conditions.