Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors

Hogben, Hannah J.; Biskup, Till; Hore, P. J.

doi:10.1103/physrevlett.109.220501

Cited by 74 publications

(104 citation statements)

References 36 publications

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“…Due to the quantum mechanical nature of RP mechanism, the effect of entanglement on the RP based compass has been investigated in terms of singlet yield 13, 14, 16, 19, 20, 30 . Here, we reconsider the effect of entanglement on the RP based compass in terms of QFI, and use concurrence 61 to quantify entanglement.…”

Section: Resultsmentioning

confidence: 99%

Quantifying Magnetic Sensitivity of Radical Pair Based Compass by Quantum Fisher Information

Guo

Zou

et al. 2017

Sci Rep

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The radical pair (RP) based compass is considered as one of the principal models of avian magnetoreception. Different from the conventional approach where the sensitivity of RP based compass is described by the singlet yield, we introduce the quantum Fisher information (QFI), which represents the maximum information about the magnetic field’s direction extracted from the RP state, to quantify the sensitivity of RP based compass. The consistency between our results and experimental observations suggests that the QFI may serve as a measure to describe the sensitivity of RP based compass. Besides, within the framework of quantum metrology, we give two specific possible measurement schemes and find that the conventional singlet yield is corresponding to the measurement of total angular momentum. Moreover, we show that the measurement of fluctuation of the total magnetic moment is much more accurate than the singlet yield measurement, and is close to the optimal measurement scheme. Finally, the effects of entanglement and decoherence are also discussed in the spirit of our approach.

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Section: Resultsmentioning

confidence: 99%

Quantifying Magnetic Sensitivity of Radical Pair Based Compass by Quantum Fisher Information

Guo

Zou

et al. 2017

Sci Rep

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“…[38] and Hogben et al . [41]). Our present data thus provide additional support for the hypothesis of Cry1a being indeed the receptor molecule for magnetic directions.…”

Section: Discussionmentioning

confidence: 99%

Magnetoreception: activated cryptochrome 1a concurs with magnetic orientation in birds

Nießner

Denzau

Stapput

et al. 2013

J. R. Soc. Interface.

153

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The radical pair model proposes that the avian magnetic compass is based on radical pair processes in the eye, with cryptochrome, a flavoprotein, suggested as receptor molecule. Cryptochrome 1a (Cry1a) is localized at the discs of the outer segments of the UV/violet cones of European robins and chickens. Here, we show the activation characteristics of a bird cryptochrome in vivo under natural conditions. We exposed chickens for 30 min to different light regimes and analysed the amount of Cry1a labelled with an antiserum against an epitope at the C-terminus of this protein. The staining after exposure to sunlight and to darkness indicated that the antiserum labels only an illuminated, activated form of Cry1a. Exposure to narrow-bandwidth lights of various wavelengths revealed activated Cry1a at UV, blue and turquoise light. With green and yellow, the amount of activated Cry1a was reduced, and with red, as in the dark, no activated Cry1a was labelled. Activated Cry1a is thus found at all those wavelengths at which birds can orient using their magnetic inclination compass, supporting the role of Cry1a as receptor molecule. The observation that activated Cry1a and well-oriented behaviour occur at 565 nm green light, a wavelength not absorbed by the fully oxidized form of cryptochrome, suggests that a state other than the previously suggested Trp•/FAD• radical pair formed during photoreduction is crucial for detecting magnetic directions.

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“…At room temperature, charge-carrier spins in the OLED material poly[2-methoxy-5-(2 -ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) are characterized by long spin coherence and relaxation times, T 2 ≈ 350 ns and T 1 ≈ 40 µs, respectively 1 . These parameters ensure that even tiny static magnetic fields (weaker than nuclear hyperfine fields) modify spin precession of localized carriers and alter spin-permutation symmetry of the pair, which controls the yields of electron-hole recombination and dissociation 1,[10][11][12][13] . OLEDs therefore exhibit lowfield magnetoresistance [14][15][16] owing to spatial variations in the local magnetic field experienced by the pairs precessing around hydrogen nuclear magnetic moments.…”

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confidence: 99%

The spin-Dicke effect in OLED magnetoresistance

et al. 2015

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Pairs of charge-carrier spins in organic semiconductors constitute four-level systems that can be driven electromagnetically 1 . Given appropriate conditions for ultrastrong coupling 2 -weak local hyperfine fields B hyp , large magnetic resonant driving fields B 1 and low static fields B 0 that define Zeeman splittingthe spin-Dicke e ect, a collective transition of spin states, has been predicted 3 . This parameter range is challenging to probe by electron paramagnetic resonance spectroscopy because thermal magnetic polarization is negligible. It is accessed through spin-dependent conductivity that is controlled by electron-hole pairs of singlet and triplet spin-permutation symmetry without the need of thermal spin polarization 4 . Signatures of collective behaviour of carrier spins are revealed in the steady-state magnetoresistance of organic light-emitting diodes (OLEDs), rather than through radiative transitions. For intermediate B 1 , the a.c.-Zeeman e ect appears. For large B 1 , a collective spin-ensemble state arises, inverting the current change under resonance and removing power broadening, thereby o ering a unique window to ambient macroscopic quantum coherence.Macroscopic phase coherence is a hallmark of many exotic states of matter such as superconductivity, ferromagnetism or BoseEinstein condensation. Such coherence may also emerge between two-level systems, where it is mediated by electromagnetic fields, as described by the Dicke effect in collisional narrowing 5 and superradiance 6 . Collective behaviour may already arise within a pair of interacting two-level systems 7 , an observation that can potentially be extended to the prototypical two-level system of an electron spin. For pairs of charge-carrier spins in organic semiconductors, with driving fields B 1 exceeding the hydrogen-induced random local hyperfine field 1 B hyp and approaching the magnitude of the static magnetic field B 0 , a collective macroscopic spin phase has been predicted to emerge 3 . Under these conditions, when the spin-Rabi splitting becomes comparable to the Zeeman splitting, the electromagnetic field links individually resonant spin pairs together, forming a spin-Dicke state analogous to that in the dipolar Dicke effect [5][6][7] . These macroscopic effects are observable through measurements of electronic recombination rates, which depend on spin-permutation symmetry of the pair 8 .We monitor the electron-hole recombination current in an OLED, where positive and negative charges are injected into a thin film of an organic semiconductor from opposite electrodes. As the charges drift through the material, they can capture each other on intermolecular length scales owing to weak dielectric screening. These weakly coupled intermolecular electron-hole pairs 9 can ultimately recombine on individual molecules to form a molecular excited state, or exciton, which gives rise to electroluminescence. The subsequent discussion focuses on carrier pairs and not on excitons, which have spin S = 0 or 1. Because the carriers possess spi...

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Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors

Cited by 74 publications

References 36 publications

Quantifying Magnetic Sensitivity of Radical Pair Based Compass by Quantum Fisher Information

Quantifying Magnetic Sensitivity of Radical Pair Based Compass by Quantum Fisher Information

Magnetoreception: activated cryptochrome 1a concurs with magnetic orientation in birds

The spin-Dicke effect in OLED magnetoresistance

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