Szczegóły publikacji

All particles of the same type are indistinguishable, according to a fundamental quantum principle. This entails a description of many-particle states using symmetrised or anti-symmetrised wave functions, which turn out to be formally entangled. However, the measurement of individual particles is hampered by a mode description in the second-quantised theory that masks this entanglement. Is it nonetheless possible to use such states as a resource in Bell-type experiments? More specifically, which states of identical particles can demonstrate non-local correlations in passive linear optical setups that are conventionally taken to be a classical component of the experiment? Here, the problem is fully solved for multi-particle states with a definite number of identical particles. We show that all fermion states and most boson states provide a sufficient quantum resource to exhibit non-locality in passive linear optics. The only exception is a special class of boson states that are reducible to a single mode, which turns out to be locally simulable for any passive linear optical experiment. This finding hints at an intimate connection between the fundamental principle of particle indistinguishability and Bell non-locality, which turns out to be observable with very modest optical means for almost every state of identical particles.