An experimental setup for testing quantum nonlocality of
N qubits is proposed. This method is a generalization of the optical setup proposed by Banaszek and W\'odkiewicz [Phys. Rev. Lett. 82, 2009 (1999)]. The quantum nonlocality of
N qubits can be obtained through its violation of
N-qubit Bell inequalities. The correlation function measured in the experiment is described by the Wigner function. The effect of inefficient detector is also considered.
Quantum physics provides results at information processing tasks that are unattainable by any classical theory. The aim of this thesis is to identify and characterize quantum entanglement and quantum nonlocality, the key resources used at quantum information protocols. We consider the problem of finding better experimental schemes to detect entangled states. For that, we study approximate physical realizations to non-physical processes, which provide the most efficient method to identify entanglement. We prove that many of these physical approximations have a simple experimental implementation. We then study characterization of quantum nonlocality. We introduce a method using the multipartite scenario, where more than two parties are involved, which provides several results on bipartite and multipartite quantum nonlocality. First, we prove that there exist quantum states which contain full multipartite nonlocality, which consist of the strongest kind of nonlocality. then, we prove that the combined use of several copies of a state can activate its nonlocal properties. In particular, this holds for bipartite and genuine multipartite nonlocality. Finally, we characterize quantum nonlocality by distinguishing it from stronger-than-quantum nonlocality. We construct a multipartite game for which classical and quantum players perform equally well, but for which supre-quantum players can sometimes provide an advantage. Our results suggest that physical resources might obbey a generalized no-signaling principle ( according to which ther's no instantaneous communication).
An optical scheme for simulating nonlocality distillation is proposed in post-quantum regime. The nonlocal boxes are simulated by measurements on appropriately pre- and post-selected polarization entangled photon pairs, i.e. post-quantum nonlocality is simulated by exploiting fair-sampling loophole in a Bell test. Mod 2 addition on the outputs of two nonlocal boxes combined with pre- and post-selection operations constitutes the key operation of simulating nonlocality distillation. This scheme provides a possible tool for the experimental study on the nonlocality in post-quantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones.