Dark state population determines magnetic sensitivity in radical pair magnetoreception model

Area of Science:

• Quantum Biology
• Biophysics
• Chemical Physics

Background:

• The precise mechanisms of quantum effects, including coherence and entanglement, in biological systems like the radical pair (RP) compass remain incompletely understood.
• Investigating the factors that determine singlet yield is crucial for elucidating these quantum biological processes.

Purpose of the Study:

• To clarify the role of quantum coherence and entanglement in the radical pair compass.
• To determine the primary factors governing singlet yield in this system.

Main Methods:

• Calculated singlet yields using two initial states within the dark state basis of the two-electron Zeeman energy operator (TEZE).
• Compared singlet yields between a coherent state and a state with removed dark state coherence.

Main Results:

• Singlet yields were identical for both the coherent and non-coherent dark states, indicating dark state population is the key determinant.
• Quantum coherence and entanglement showed minimal contribution to the singlet yield.
• Dark state population and singlet yield anisotropy are sensitive to vertical magnetic noise, while orientation is robust to parallel magnetic noise.

Conclusions:

• Dark state population, rather than coherence or entanglement, completely dictates the singlet yield in the radical pair compass.
• The dark states form a decoherence-free subspace, enhancing robustness to parallel magnetic noise and hyperfine coupling.
• Findings offer a refined understanding of quantum effects in biological navigation.