Coherence-assisted non-Gaussian measurement-device-independent quantum key distribution

Abstract

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

Non-Gaussian operations in measurement device independent quantum key distribution

“…Such a discourse would be of immense interest to experimentalists in selecting the most optimal state for QKD based on transmission distances, noise robustness and/or coherence. While it has already been shown that a small amount of coherence is a actu-ally helpful process in the case of photon subtraction [40], we find that it is true for photon addition and catalysis too. This reinforces the idea that non-Gaussianity coupled with coherence leads to better performance in CV MDI QKD.…”

“…The latter has been studied in depth in Ref. [40]. The probability of n photon detections as a function of τ is plotted in Figs.…”

“…While CV MDI QKD has been well studied using Gaussian states like two mode squeezed vacuum (TMSV), few recent studies have shown that non-Gaussianity [31][32][33][34][35][36][37][38][39] and coherence [40] can have a major impact on maximizing the transmission distances. It might be noted that the desired non-gaussianity could be induced in many ways such as photon subtraction, photon addition, catalysis etc.…”

“…While the case of photon subtraction has been studied in full depth, the process of photon catalysis has been explored to some extent. Furthermore, the impact of coherence on CV MDI QKD protocols has only been made possible in the case of photon subtraction, where it was shown to be quite advantageous [40]. However, a general treatment of these non-Gaussian processes along with fiducial coherence has been not been attempted due to the difficulty in obtaining closed form solution for the covariance matrix -a primary ingredient in Gaussian modulated CV QKD.…”

Nonclassicality and entanglement properties of non-Gaussian entangled states via a superposition of number-conserving operations

“…In addition, it is worth noting that such a GSP operation can be easily implemented using linear optical devices and parametric down-converters [37]. Interestingly, the performance of continuous variable quantum key distribution can also be improved further using the TMSC instead of the TMSV [38]. Specially, larger coherence values are detrimental to the performance, but a small amount of coherence is more favorable for achieving maximum transmission distance.…”