Comment on "Quantum Control and Entanglement in a Chemical Compass"

TL;DR

This comment critiques a previous study on quantum entanglement in avian magnetic sensors, showing that neglecting decoherence leads to unphysical predictions about entanglement duration and sensor sensitivity.

Contribution

It clarifies the importance of decoherence and reaction time in accurately modeling entanglement in biochemical sensors, correcting prior overestimations.

Findings

Entanglement lifetime is limited by reaction time.

Neglecting decoherence overestimates entanglement duration.

Previous models predict unphysical sensor sensitivities.

Abstract

In this comment we show that the avian compass entanglement considerations of J. Cai, G. G. Guerreschi and H. J. Briegel (Phys. Rev. Lett. 104, 220502 (2010)) result in unphysical predictions on the magnetic sensitivity of this biochemical sensor. As well known from a series of papers on precision measurements and detailed derivations of standard quantum limits, not taking into account decoherence results in an overestimate of the entanglement lifetime, and this is the case at hand. The entanglement lifetime is wrongly assumed by the authors to be independent of the reaction time (the inverse of the recombination rate) and hence it is grossly overestimated. This is so because the spin coherence lifetime is limited by the reaction time, and the entanglement lifetime cannot be any longer.