TY  - JOUR
A1  - Menzel, Ralf
A1  - Heuer, Axel
A1  - Milonni, Peter W.
T1  - Entanglement, Complementarity, and Vacuum Fields in Spontaneous Parametric Down-Conversion
T2  - Atoms
N2  - Using two crystals for spontaneous parametric down-conversion in a parallel setup, we observe two-photon interference with high visibility. The high visibility is consistent with complementarity and the absence of which-path information. The observations are explained as the effects of entanglement or equivalently in terms of interfering probability amplitudes and also by the calculation of a second-order field correlation function in the Heisenberg picture. The latter approach brings out explicitly the role of the vacuum fields in the down-conversion at the crystals and in the photon coincidence counting. For comparison, we show that the Hong-Ou-Mandel dip can be explained by the same approach in which the role of the vacuum signal and idler fields, as opposed to entanglement involving vacuum states, is emphasized. We discuss the fundamental limitations of a theory in which these vacuum fields are treated as classical, stochastic fields.
KW  - complementarity
KW  - vacuum fields
KW  - entanglement
KW  - Hong-Ou-Mandel effect
KW  - spontaneous parametric down-conversion
Y1  - 2019
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/51056
SN  - 2218-2004
VL  - 7
IS  - 1
PB  - MDPI
CY  - Basel
ER  -