principles of noise assisted transport in networks

Imperial College London

Institute for Mathematical Sciences&

Quantum Optics and Laser Science GroupBlackett Laboratory

Imperial College London

http://www.imperial.ac.uk/quantuminformation

Principles of Noise Assisted Transport in Networks

Martin B Plenio

In collaboration with: Animesh Datta & Filippo Caruso (Imperial College London, UK) Alex Chin and Susana Huelga (Univ. Hertfordshire, UK)

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Lisbon, 8th July 2009

Noise seems a problem here as it destroys quantum coherence

Lisbon, 8th July 2009

Weak coherent driving

Weak response

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Weak coherent driving + weak noise give a strong coherent response.

Stochastic resonance

Noise

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Biological systems can use noise to improve their sensitivity to weak coherent signals

Can we use this in quantum mechanics ?

Noise can be good for you in quantum mechanics too for entanglement generation and preservation !

Huelga & Plenio, PRA 1999, PRA 2000 & PRL 2002 & PRL 2007

See also overview talk by Susana Huelga Friday

Lisbon, 8th July 2009

Clicks

Time

Clicks

Time

A Fundamental Experiment

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A Fundamental Experiment

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Clicks

Time

Clicks

Time

A Fundamental Experiment

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Green sulphur Bacteria

Photosynthesis

A black smoker in the Atlantic Ocean ~ 2000m deep

Y.C. Cheng and G.R. Fleming, Annu. Rev. Phys. Chem. 60, 241 (2009)

Lisbon, 8th July 2009

Green sulphur Bacteria

Exciton Transport in Photosynthesis

Reaction Centre

CO2+ 2 H S2

+ energy

CH O2

+ 2 S + H O2

Lisbon, 8th July 2009

Green sulphur Bacteria

Reaction Centre

Exciton Transport in Photosynthesis

CO2+ 2 H S2

+ energy

CH O2

+ 2 S + H O2

Lisbon, 8th July 2009

Transfer to reaction centre

Green sulphur Bacteria

Reaction Centre

Exciton Transport in Photosynthesis

CO2+ 2 H S2

+ energy

CH O2

+ 2 S + H O2

Lisbon, 8th July 2009

Loss of excitation

Transfer to reaction centre

Reaction Centre

CO2+ 2 H S2

+ energy

CH O2

+ 2 S + H O2

M.B. Plenio and S.F. Huelga, New J. Phys. 10, 113019 (2008)

Exchange of excitation

Dephasing

Lisbon, 8th July 2009

Noise Assisted Transport and Photosynthesis

No dephasing

Some dephasing

Plenio & Huelga, New J. Phys. 2008 Mohseni, Rebentrost, Lloyd, Aspuru-Guzik, J. Phys. Chem. 2008

More dephasing

Lisbon, 8th July 2009

Physical Origin of Noise Assisted Transport

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Exciton Transport in Photosynthesis

Show Movie 1: No dephasing Initial excitation in site 1

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Two differenttime scales !

Exciton Transport in Photosynthesis

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Clicks

Time

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Time

Destructive Interference and Invariant States

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Destructive Interference and Invariant States

J J

Reactioncenter

=

Lisbon, 8th July 2009

Destructive Interference and Invariant States

Tran

sfer

eff

icie

ncy

J J

=

Reactioncenter

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Noise Inhibits Destructive Interference

Decoherence inhibits destructive interference !

Tran

sfer

eff

icie

ncy

Reduction ofdestructive interference

J J

Reactionscenter

Reactioncenter

=

Lisbon, 8th July 2009

Destructive Interference and Invariant States

Invariant state:

Two atoms in the same location:

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Dephasing on site 1 only

Show Movie1a: Small dephasing on site 1 only

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Dephasing on site 1 only

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Destructive Interference and Invariant States

not invariant under Hamiltonian evolution !

Different energy splitting:

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Static disorder inhibits destructive interference !

Disorder Inhibits Destructive Interference

J J

J JDestructiveinterference

Reactioncenter

Reduction ofdestructive interference

Reactioncenter

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Disorder Inhibits Destructive Interference

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The Hamiltonian of the FMO complex

Quite strong static disorder compared to coupling strengths !

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Bridging the gap: Enhanced transport via line broadening

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Dephasing Noise on Site 3 only

Play Movie1b: Dephasing noise only on site 3

Play Movie1ab: Same amount of dephasing noise now only on site 3

Lisbon, 8th July 2009

Dephasing Noise on Site 3 only

Lisbon, 8th July 2009

No line broadening, No transfer!Line broadening does enhance transfer!

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J J

destructive interference

-J -J

Spatially Correlated Noise

effect ofnoise reduced

J J

destructive interference

+J -J

effect ofnoise enhanced

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local dephasing without correlations

dephasing with non-local correlations

T=5 ps

Therefore, correlated noise does not lead to decisive improvements in this setting!

Spatially Correlated Noise

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J J

destructive interference

J J

Loss Enhanced Transport

destructive interference

reduced

J J

excitationlost

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Noise Assisted Transport and Photosynthesis

No dephasing

Some dephasing

More dephasing

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Reduction of destructive interference

Inhibition of coupling through dephasing

Dependence on Noise Strength

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Two differenttime scales !

Robustness against strong static disorder compared to coupling strengths (i.e. 20%)!

optimal dephasing

no dephasing

Robustness of Noise Assisted Transport

Lisbon, 8th July 2009

F.Caruso., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, to be submitted

Entanglement Dynamics

Lisbon, 8th July 2009

F.C., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, arxiv:0901.4454 (2009)

|01>-|10>

J J

reduced destructive interferencedestructive interference

J

Each process open additional pathways for propagation

Lisbon, 8th July 2009

The Fundamental Mechanisms

Dephasing can reduce destructive interference

Energy mismatch can reduce destructive interference

Dephasing noise increases overlap of energy levels

Each process open additional pathways for propagation

Plenio & Huelga, New J. Phys. 10, 113019 (2008)Caruso, Chin, Datta, Huelga, Plenio, arxiv:0901.4454 [quant-ph]

Lisbon, 8th July 2009

Can we improve solar cellsbased on this idea ?

More generally: Adding the right kind of noise, to the right kind of nano-structure can improve its performance.

Engineer system to generate constructive interplay between quantum dynamics and noise

Lisbon, 8th July 2009

This talk was based on

Plenio & Huelga, New J. Phys. 10, 113019 (2008)

Caruso, Chin, Datta, Huelga, Plenio, E-Print arXiv:0901.4454

Caruso, Chin, Datta, Huelga, Plenio, to be submitted

Lisbon, 8th July 2009

We move to Ulm to establish Center for Quantum Engineering

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