We show that the coherent superposition of photon subtraction and addition applied to each local mode of a two-mode entangled state can enhance the nonlocality manifested by the violation of a Bell inequality. A two-mode squeezed state is used as an input state for this demonstration with four different Bell inequalities employed: Bell inequalities adopting displaced parity operator, pseudospin operator, homodyne measurement, and conditional entropy, respectively. We find that the coherent operation significantly enhances the nonlocality remarkably in the weak squeezing limit, compared with other possible non-Gaussian operations. It can also give a maximal Bell violation with a very small squeezing for the inequalities with pseudospin operator and conditional entropy.
© 2012 Optical Society of America
(270.6570) Quantum optics : Squeezed states
(270.5585) Quantum optics : Quantum information and processing
Original Manuscript: November 28, 2011
Manuscript Accepted: December 22, 2011
Published: April 6, 2012
Jiyong Park, Su-Yong Lee, Hai-Woong Lee, and Hyunchul Nha, "Enhanced Bell violation by a coherent superposition of photon subtraction and addition," J. Opt. Soc. Am. B 29, 906-911 (2012)