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Paper 1

Avoiding the Detector Blinding Attack on Quantum Cryptography

Z L Yuan, J F Dynes, A J Shields

Year

2010

Journal

arXiv preprint

DOI

arXiv:1009.6130

arXiv

1009.6130

We show the detector blinding attack by Lydersen et al [1] will be ineffective on most single photon avalanche photodiodes (APDs) and certainly ineffective on any detectors that are operated correctly. The attack is only successful if a redundant resistor is included in series with the APD, or if the detector discrimination levels are set inappropriately.

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Paper 2

Structured Negativity: A physically realizable measure of entanglement based on structural physical approximation

Anu Kumari, Satyabrata Adhikari

Year

2022

Journal

arXiv preprint

DOI

arXiv:2209.03909

arXiv

2209.03909

Quantification of entanglement is one of the most important problem in quantum information theory. In this work, we will study this problem by defining a physically realizable measure of entanglement for any arbitrary dimensional bipartite system $ρ$, which we named as structured negativity $(N_S(ρ))$. We have shown that the introduced measure satisfies the properties of a valid entanglement monotone. We also have established an inequality that relate negativity and the structured negativity. For $d\otimes d$ dimensional state, we conjecture from the result obtained in this work that negativity coincide with the structured negativity when the number of negative eigenvalues of the partially transposed matrix is equal to $\frac{d(d-1)}{2}$. Moreover, we proved that the structured negativity not only implementable in the laboratory but also a better measure of entanglement in comparison to negativity. In few cases, we obtain that structure negativity gives better result than the lower bound of the concurrence obtained by Albeverio [Phys. Rev. Lett. \textbf{95}, 040504 (2005)].

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