Robustness of bipartite Gaussian entangled beams propagating in lossy channels

• Published in: Nature photonics Vol. 4; no. 12; pp. 858 - 861
• Main Authors: Barbosa, F. A. S., Coelho, A. S., de Faria, A. J., Cassemiro, K. N., Villar, A. S., Nussenzveig, P., Martinelli, M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2010; Nature Publishing Group
• Subjects: 639/624/400/482; Applied and Technical Physics; Applied sciences; Beams (radiation); Channels; Classical and quantum physics: mechanics and fields; Constraining; Cryptography; Entanglement; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Gaussian; letter; Optical telecommunications; Optics; Physics; Physics and Astronomy; Quantum communication; Quantum information; Quantum Physics; Robustness; Tasks; Telecommunications; Telecommunications and information theory; Wave optics; Wave propagation, transmission and absorption; Gaussian beam; Optical beam; Quantum entanglement; Electromagnetic wave propagation; Optical communication; Quantum information; Quantum communication
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2010.222

Subtle quantum properties offer exciting new prospects in optical communications. For example, quantum entanglement enables the secure exchange of cryptographic keys 1 and the distribution of quantum information by teleportation 2 , 3 . Entangled bright beams of light are increasingly appealing for such tasks, because they enable the use of well-established classical communications techniques 4 . However, quantum resources are fragile and are subject to decoherence by interaction with the environment. The unavoidable losses in the communication channel can lead to a complete destruction of entanglement 5 , 6 , 7 , 8 , limiting the application of these states to quantum-communication protocols. We investigate the conditions under which this phenomenon takes place for the simplest case of two light beams, and analyse characteristics of states which are robust against losses. Our study sheds new light on the intriguing properties of quantum entanglement and how they may be harnessed for future applications. Quantum entanglement — used for quantum key distribution, communication and teleportation — is a fragile resource. Researchers investigate the conditions under which optical loss destroys entanglement, and report states that are particularly robust to such losses.