Nonexistence of entanglement sudden death in dephasing of high NOON states

• Published in: Optics letters Vol. 34; no. 3; p. 268
• Main Authors: Al-Qasimi, Asma, James, Daniel F V
• Format: Journal Article
• Language: English
• Published: United States 01.02.2009
• ISSN: 0146-9592
• DOI: 10.1364/OL.34.000268

We study the dynamics of entanglement in continuous variable quantum systems. Specifically, we study the phenomena of entanglement sudden death (ESD) in general two-mode-N-photon states undergoing pure dephasing. We show that for these circumstances, ESD never occurs. These states are generalizations of the so-called high NOON states (i.e., a superposition of N photons in the first mode, O in the second, with O photons in the first, N in the second), shown to decrease the Rayleigh limit of lambda to lambda/N, which promises great improvement in resolution of interference patterns if states with large N are physically realized [Phys. Rev. Lett.85, 2733 (2000)]. However, we show that in dephasing NOON states, the time to reach some critical visibility Vcrit, scales inversely with N2. On the practical level, this shows that as N increases, the visibility degrades much faster, which is likely to be a considerable drawback for any practical application of these states.