Agenda

Résumé : Quantum nonlocality describes a stronger form of quantum correlation than that of entanglement. It refutes Einstein’s belief of local realism and is among the most distinctive and enigmatic features of quantum mechanics. It is a crucial resource for achieving quantum advantages in a variety of practical applications, ranging from cryptography and certified random number generation to self-testing. While the few-body case is well-explored, the detection of nonlocality especially in quantum many-body systems, is notoriously challenging. In this talk, we will start with some basics on nonlocality and entanglement and then motivate the usage of energy as a detector for many-body Bell nonlocality and the certification of Bell correlation depth. If an appropriate Hamiltonian is chosen, it can be used as a Bell correlation witness and by variationally decreasing the energy of a many-body system across a hierarchy of thresholds, we certify an increasing Bell correlation depth from experimental data. In the second half of the talk we will transition from theory to experiment and look at the experimental results of a 73 qubit experiment certifying both Bell-operator correlations on 73 qubits and a Bell-operator correlation depth of 24 qubits. K. Wang et al., Probing Many-Body Bell Correlation Depth with Superconducting Qubits, Phys. Rev. X 15, 021024 (2025).