Violation of Bell inequality is a prominent detection method for quantum correlations present in composite quantum systems, both in finite and infinite dimensions. We investigate the consequence of the violation of local realism based on pseduospin operators when photons are added or subtracted in a single mode or in both the modes of the two-mode squeezed states of light in the presence of noise. In the noiseless situation, we show that for addition (subtraction) of photons in a single mode, there is an overall enhancement in the maximal violation, although we observe an interplay between monotonicity and nonmonotonicity in the violation of Bell inequality depending on the squeezing strength. Moreover, we report that for low squeezing or low number of photons added or subtracted, subtraction in both the modes can lead to higher violation of local realism than that in the case of addition. For any choice of parameters, such ordering is not seen if one compares their entanglement contents. In the event of a faulty twin-beam generator, we obtain a lower than expected squeezing in the state. In such a case, or in imperfect photon addition (subtraction) or under local noise, we find that the violation of local realism by the noise-affected two-mode squeezed states always decreases. Interestingly, however, we notice that photon addition (subtraction) can in general help to conquer the ill effects of noise by enhancing the violation of local realism or by transforming nonviolating states to violating ones, thereby acting as an activating agent.

• Received 26 July 2018

DOI:https://doi.org/10.1103/PhysRevA.98.052131