There was a minor error in the published version of our Letter, which does not change the conclusions. In Eqs. (5) and (6) of the published version, V n11 should be replaced by V n throughout. The matrix r n af , just prior to Eq. (6), should be replaced byAll of the above changes result in the interchange of C and S in Eq. (8) of the published version with the new expression for L n given byThe plot of L n with t then changes slightly and is redrawn in this Erratum as Fig. 1.From the new Fig. 1, it is clear that corresponding to a projection onto the j0͘, j1͘ subspace, the atom-cavity state is now always entangled except for values of t np͞2. Compared with the earlier version of the Letter, this is a much larger domain for t, for which the state remains entangled. Thus, our conclusions about the presence of entanglement are strengthened. 0 1 2 3 4 5 6 7 8 9 1 0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 Λ n t FIG. 1. Plots of the time variation of the inseparability expression L for three values of n. The fastest oscillating curve is for n 100, the next fastest for n 10, and the slowest oscillating curve is for n 0.

Quantum information processing rests on our ability to manipulate quantum superpositions through coherent unitary transformations, and to establish entanglement between constituent quantum components of the processor. The quantum information processor (a linear ion trap, or a cavity confining the radiation field for example) exists in a dissipative environment. We discuss ways in which entanglement can be established within such dissipative environments. We can even make use of a strong interaction of the system with its environment to produce entanglement in a controlled way.

Non-Gaussian operations on two mode squeezed vacuum states (TMSV) in continuous variable measurement device independent quantum key distribution (CV-MDI-QKD) protocols have been shown to effectively increase the total transmission distances drastically. In this paper we show that photon subtraction on a two mode squeezed coherent (PSTMSC) state can further improve the transmission distances remarkably. To that end we also provide a generalized covariance matrix corresponding to PSTMSC, which has not been attempted before. We show that coherence, defined as the amount of displacement of vacuum state, along with non-Gaussianity can help improve the performance of prevalent CV-MDI-QKD protocols. Furthermore, since we use realistic parameters, our technique is experimentally feasible and can be readily implemented. * chandankumar@iisermohali.ac.in † jaskaransinghnirankari@iisermohali.ac.in ‡ soumyabose@iisermohali.ac.in § arvind@iisermohali.ac.in

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