document: Delayed-choice entanglement swapping with vacuum-one-photon quantum states We report the experimental realization of a recently discovered quantum-information protocol by Peres implying an apparent nonlocal quantum mechanical retrodiction effect . The demonstration is carried out by a quantum optical method by which each singlet entangled state is physically implemented by a two-dimensional subspace of Fock states of a mode of the electromagnetic field , specifically the space spanned by the vacuum and the one-photon state , along lines suggested recently by E. Knill et al. -LSB- Nature -LRB- London -RRB- 409 , 46 -LRB- 2001 -RRB- -RSB- and by M. Duan et al. -LSB- ibid . 414 , 413 -LRB- 2001 -RRB- -RSB-
doc_bio_tags: O O O O O O O O O O O O O O O O O O O O O O O B I I I I O O O O O O O O B I I O O O B I I O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
extractive_keyphrases: nonlocal quantum mechanical retrodiction effect quantum optical method singlet entangled state fock states
abstractive_keyphrases: delayed-choice entanglement quantum-information two-dimensional subspace state entanglement electromagnetic field mode vacuum-one-photon quantum states one-photon state vacuum state