Title: Sustained quantum coherence in the Avian compass
http://arxiv.org/abs/0906.3725

Abstract: Tremendous efforts are underway to build technologies that harness the deep quantum phenomena of superposition and entanglement. These properties have proven fragile, often decaying rapidly unless cryogenic temperatures are used. Could life have evolved to exploit such phenomena? Certain migratory birds have the ability to sense very subtle variations in the Earth's magnetic field. Here we use recent experimental observations together with the well developed `radical pair' model of the avian compass, and employ a master equation with various decoherence operators in order to examine the system's vulnerability to environmental noise. Remarkably, the room temperature noise tolerance in this natural system appears greater than that of the best man-made molecular radical or solid state singlet/triplet devices. We find that entanglement, though probably not an essential feature of this process, appears to persist to tens of microseconds, or more.

Abstract: We consider a chain of harmonic oscillators with dipole-dipole interaction between nearest neighbours resulting in a van der Waals type bonding. The binding energies between entangled and classically correlated states are compared. We apply our model to DNA. By comparing our model with numerical simulations we conclude that entanglement may play a crucial role in explaining the stability of the DNA double helix.

Abstract: The entanglement properties of the phase transition in a two dimensional harmonic lattice, similar to the one observed in recent ion trap experiments, are discussed both, for finite number of particles and thermodynamical limit. We show that for the ground state at the critical value of the trapping potential two entanglement measures change abruptly. Entanglement thus indicates quantum phase transitions in general; not only in the finite dimensional case considered in [Phys. Rev. Lett. {\bf 93}, 250404 (2004)]. Finally, we consider the thermal state and compare its exact entanglement with the result of the temperature entanglement witness, introduced in [Phys. Rev. A {\bf 77} 062102 (2008)].