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Briefings | Space & Physics

Briefings

Scientifc AmericanBriengs: Space & Physicsconsiss of suaries of recen peer-reviewedarticles from the scientic literature. It drawshese suaries fro he journals of NaurePublishing Group, including Nature, NatureNanotechnology, Nature Photonics, NaturePhysics and he Nature Reviews journals.

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ASTROCHEMISTRY

A gift from the

starsObservatOries arOund the

world have recorded inrared

emission spectra at wavelengths

o 320 micrometers rom stars

and nebulae. These spectra were

initially considered characteris-

tics o polycyclic aromatic hydro-

carbons used-ring molecules

commonly ound in burnt ood,

tar, coal and oil.

Sun Kwok and Yong Zhang at

the University o Hong Kong

have now proposed an alterna-

tive hypothesis that these

emission spectra are character-

istic o complex organic mole-

cules with disorganized struc-

tures. They examined the emis-

sion spectra rom several

nebulae and pro-planetary neb-

ulae, including the Orion Bar

nebula, and ound that the most

tting model would be i the or-

ganic molecules contained a

mixture o aliphatic branches

and aromatic rings, and not justaromatic rings alone.

In act, recent laboratory anal-

yses have identied organic mole-

cules with a chemical structure

similar to that described above in

the Murchison meteorite. The re-

searchers suggest that organic

molecules might exist throughout

the universe, and that meteorites

might have carried these mole-

cules rom distant galaxies to our

solar system.

Edward Duca,Nature China

Nature doi: 10.1038/nature10542 (2011)

PHYSICS

Nanoear hearssmall soundsby using laser beams to trap a

gold nanoparticle, researchers in

Germany have developed a sensi-

tive sound-wave detector.

Tightly ocused laser beams,

known as optical tweezers, have

been used to manipulate micro-

scopic objects or two decades.

Andrey Lutich, Jochen Feld-

mann and their co-workers at

the LudwigMaximilians Univer-

sity in Munich used a similar ap-

proach: they suspended a

60-nanometre gold nanoparticle

in water in the ocal spot o a

laser beam. They sent sound

waves through the water and

measured changes in the parti-

cles constrained motion. The au-

thors calculate that the nanopar-

ticle can pick up sounds as lowas 60 decibels, making the set-

up a million times more sensi-

tive than the human ear.

Eugenie Samuel Reich,

Nature

Phys. Rev. Lett. doi: 10.1103/

PhysRevLett.108.018101 (2012)

ELECtRON BEAmS

An atom-sized

vortexelectrOn beams are typically

plane waves. This means that the

beam phase is identical or all

points in a plane perpendicular

to the beam direction. The phase

o an electron vortex beam, on

the other hand, describes a

spiral. As a result, vortex beams

carry orbital angular moment

and magnetic moment, which

leads to unique interactions with

matter. Jo Verbeeck o the Uni-

versity o Antwerp and col-

leagues rom Austria, the Neth-

erlands and Canada have now

demonstrated an electron vortex

beam with a diameter o lessthan 1.2 .

Electron vortex beams were

rst created by passing a plane

wave beam through a graphite

lm that spontaneously ormed

a spiral structure, and acted as a

phase plate. This was dicult to

reproduce and gave limited con-

trol over the resulting beam. Ver

beeck and co-workers had im-

proved on this approach by cre-

ating a vortex beam with a

holographic mask inside a trans-

mission electron microscope.

However, the eective beam di-

ameter was several micrometers

Verbeek and colleagues have

now reduced this beam diameter

to atomic dimensions by placing a

holographic mask in the con-

denser plane o a state-o-the-art

microscope with double aberra-

tion correction. At 1.2 , the beam

size is comparable to the size o

the 2porbital in a nitrogen atom

(see image; let and right panels

show the beam and the 2porbitalrespectively, drawn approximately

to scale). The tiny vortex beam

may allow atomic-resolution

mapping o magnetic states.

Michael Segal

Nature Nanotechnology

Appl. Phys. Lett. doi: 10.1063/1.3662012

(2011)

TECHNIQUES

Cooling bynumberslike electrOns trapped in the

potential o a nucleus, bosonic

atoms residing at the individual

sites o an optical lattice a peri-

odic structure dened by inter-

ering laser beams can occupy

discrete motional orbitals.

Waseem Bakr and colleagues

have now implemented a tech-

nique or deterministically con-

trolling the distribution o atoms

COURTNEYKEATINg/ISTOCKPHOTO

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On the COver

Light rom the Orion Nebula,

one o the most arresting

sights in the night sky,

suggests that some highly

interesting mixture o

complex organic molecules

can be ound near these

stellar remnants. See page 2.

Credit: ESO/J. Emerson/

VISTA/Cambridge

Astronomical Survey Unit

Scientic American Briengs, Space & Physics, Volume 1, Number 2,February 2012, published monthly by Scientic American, a division ofNature America, Inc., 75 Varick Street, 9th Floor, New York, NY 10013-1917.

Subscription rates: 1 year (12 issues) $19.95 (USD).Please send subscription correspondence, including changeof e-mail and postal addresses to:Scientic American Briengs, Box 3187, Harlan, IA 51537.E-mail address for subscription inquires:[email protected] address for general inquires:[email protected].

Subscription inquires:U.S. and Canada: 800-333-1199; other: +1-515-248-7684.

Copyright 2012 Scientic American, a division of Nature America, Inc.All rights reserved.

across these dierent energy

states, and establish it as a new

means o cooling quantum gases.

The key is a mechanism

Bakret al. call orbital excitationblockade. They transer ground-

state atoms to a higher orbital by

modulating the lattice depth at a

suitable requency; but once one

atom is transerred, it shits the

energy levels to a degree that

other atoms at the same site are

pushed o-resonance the rst

excitation blocks urther ones.

Bakr and colleagues use this

mechanism to reshue and se-

lectively remove atoms rom a

lattice with random occupation

numbers. As atom-number fuc-

tuations across the lattice are the

main source o entropy, levelling

the number o atoms at each site

amounts to cooling the gas. The

authors expect that in the uture

their method can also serve in

quantum computations on op-

tical-lattice systems.

Andreas Trabesinger,

Nature Physics


NANOTECHNOLOgY

Swirls movetiny objectsindividual cells can be ma-

nipulated by tiny vortices gener-

ated in fuids, rather than by the

potentially harmul lasers or

electric elds typically used. The

concept is the brainchild o Li

Zhang and his colleagues at the

Swiss Federal Institute o Tech-nology in Zurich, who used the

vortices to control the movement

o microscopic objects.

The team placed a tank o

water in a rotating magnetic

eld, which triggered nickel

nanowires in the tank to rotate

in turn, generating microvor-

tices. The vortices trapped poly-styrene microbeads in the water.

By controlling the movement o

the nanowires, the authors could

tightly control the movement o

the beads.

They also successully manip-

ulatedEscherichia colibacteria

using a pair o microspheres in

place o the nanowires.

Daniel Cressey,Nature

Nano Lett. 10.1021/nl2032487 (2011)

PLANETARY SCIENCE

Mercurysplasma belt

like earth, Mercury has a

magnetosphere, a zone o inter-

action between its magnetic eld

and incoming plasma rom the

Sun. But scientists have been un-

sure about whether Mercury also

has the concentration o charged

particles around its equator that

Earth does.David Schriver at the Univer-

sity o Caliornia, Los Angeles,

and his colleagues argue that

Mercury does have such a quasi-

trapped particle belt, citing sim-

ulations o the planets dynamics

and data rom instruments

aboard the MESSENGER space-

crat, which entered into orbit

around Mercury in March 2011.

The crat ploughed through an

equatorial population o 110-ki-

loelectron-volt ions and elec-

trons at a distance o about hal

the planets radius rom the

surace.

The authors compare the belt

to Earths ring current and saythat it could infuence the pat-

tern o surace weathering and

the ormation o a thin atmo-

sphere around Mercury.

Emma Maris,Nature

Geophys. Res. Lett. doi:

10.1029/2011GL049629 (2011)

WAVEgUIDES

LuminousrepulsionenhancedWhen adielectric particle is ex-

posed to a strong optical gra-

dient it becomes electrically po-

larized and subject to an attrac-

tive orce in the direction o

increasing eld strength. This is

the principle by which optical

tweezers are able to trap and ma

nipulate living cells and other

microscopic objects.A similar orce can be gener-

ated between two light-carrying

microscopic (and nanoscopic)

waveguide structures. Moreover,

the sign o the orce can be

tuned rom attractive to repul-

sive by shiting the phase o the

light travelling in one waveguide

relative to the other which is

potentially useul or optome-

chanical sensing and switching

applications. Unortunately, the

magnitude o such orces ismuch less than the orce exerted

by optical tweezers. And at small

separations the sign is invariably

attractive.

Ardavan Oskooi and col-

leagues propose a way to in-

crease the repulsion between

waveguides. Their calculations

suggest that the key is to cut

each waveguide in hal, as semi-

circular waveguides perorm

much better than circular. This

works even better in the case oCREDIT:MARKEVANS/ISTOCKPHOTO

Mercry.

NASA/JOHNSHO

PKINSUNIVERSITYAPPLIEDPHYSICS

LABORATORY/CA

RNEgIEINSTITUTIONOfWASHINgTON

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photonic crystal waveguides,

which show a 30-old increase in

repulsive orce that remains re-

pulsive even at small

separations.Ed Gerstner,

Nature Physics

Opt. Lett. doi: 10.1364/OL.36.004638

(2011)

NANOELECTROMECHANICAL SYSTEMS

Keeping thenoise down

any device that amplies a

signal inevitably adds noise, andquantum mechanics prevents

this added noise being reduced

below a certain value. It is pos-

sible to approach this quantum

limit by using superconducting

devices to ampliy electrical sig-

nals, but these devices are com-

plex. Now Francesco Massel and

co-workers at Aalto University

and the VTT Technical Research

Centre o Finland have shown

that nanomechanical resonators

can ampliy microwave signals,and that it may be possible to

reach the quantum limit with

this approach.

The Finnish team starts by

using lithography and ocused

ion-beam etching to dene a me-

chanical resonator and a micro-

wave cavity in a 150-nm-thick

layer o aluminum on a silica

surace. When a pump signal is

ed into this system, energy is

transerred rom the cavity to

the resonator i the pump re-

quency is higher than the reso-

nance requency o the cavity,

and vice versa. And i a weak

probe signal is sent into the

system when energy is beingtranserred to the resonator, this

probe can also be amplied.

Massel and co-workers show

that approximately 20 noise

quanta are added to the signal,

and predict that it should be

possible to reach the quantum

limit o adding just hal a

quantum o noise.

Peter Rodgers,


Naturedoi: 10.1038/nature10628 (2011)

OPTICAL ISOLATORS

Single-photonperformanceunWanted feedbackcaused

by refections between optical

components can have a delete-

rious eect on quantum optical

devices. Avoiding eedback re-

quires the use o optical diodes,

also known as isolators, which

support the propagation o pho-tons in one direction while pro-

hibiting propagation in the op-

posite direction. Traditional

solid-state optical isolators in-

clude Faraday rotators, which

provide isolation by rotating the

polarization o a light beam.

Now, Jung-Tsung Shen and col-

leagues at Washington Univer-

sity in St Louis, USA, have dem-

onstrated that near-complete op-

tical isolation can be achieved at

the single-photon level by cou-pling a quantum impurity to a

passive, linear waveguide that

has a locally planar, circular po-

larization. Their single-photon

optical diode operates on indi-

vidual photons, thus enabling

unidirectional propagation. Fur-

thermore, this conguration

does not rely on the use o bulk

nonlinear materials or quasi-

phase-matching and can be im-

plemented in various types o

waveguide. The researchers have

also demonstrated that the per-

ormance o their diode is not

sensitive to the intrinsic dissipa-

tion o the quantum impurity.

James BaxterNature Photonics


PhysRevLett.107.173902 (2011)

MATHEMATICS

What da Vincisaw in treesin his notebooks, the teenth-

century Italian polymath Leon-

ardo da Vinci observed that the

total cross-section o a tree re-

mains the same along its height

every time it branches. Physicists

have searched or years or an ex

planation or this phenomenon,

but have yet to nd one that is

widely accepted.

Christophe Eloy o Aix-Mar-seilles University in France

shows that the observation ol-

lows rom two assumptions

irst, that trees are ractal, or

sel-similar in nature, and,

second, that their growth is

determined by the need to

withstand wind stress on their

branches. Eloy says that the

most relevant property o wind

loads is the way it diverges to-

wards the t ips o branches.

Static loads rom ruit, snow

LUISCARLOSTORRES/ISTOCKPHOTO

Da Vincis self-portrait.

TURIN,R

OYALLIBRARY

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or ice would have a similar

eect.

Eugenie Samuel,Nature


PhysRevLett.107.258101 (2011)

PLANETARY SCIENCE

Marsdemagnetized

the sOuth Province o Mars is

almost devoid o a magnetic sig-

nature. Analyses o crustal struc-

ture, combined with demagneti-

zation models, suggest that the

lack o a magnetic signal here

may indicate a weak magnetic

eld early in Marss history.

Jaar Arkani-Hamed o the

University o Toronto and Daniel

Boutin o McGill University,

Montreal, tested whether large

asteroid impacts on Mars mayhave re-melted parts o the crust

long ater the magnetic eld had

died out, erasing the signature in

the South Province. They com-

bined analyses o crustal struc-

ture with models o impact-in-

duced demagnetization and

ound that asteroid impacts in

the South Province would have

been sucient to erase any ex-

isting magnetic signature

around the impact basin. How-

ever, they also show that the en-

tire region is devoid o a strong

magnetic signal, including areas

not aected by impacts.

Rather than undergoing an

impact-induced removal o thesignature, the entire South Prov-

ince may have instead ormed

during a period o weak mag-

netic eld strength on young

Mars.

Amy Whitchurch,

Nature Geoscience

Icarusdoi: 10.1016/

j.icarus.2011.10.023 (2011)

QUANTUM PHYSICS

Guided matterinterfering laserbeams

can refect particles a phe-

nomenon now demonstrated by

Charlotte Fabre and colleagues,

who have created a matter

mirror by crossing two inrared

beams.

Optical intererence creates a

periodic energy potential where

the two laser beams meet. By

launching a cloud o rubidium

atoms towards this mirror and

then imaging the atoms aterthey had interacted with the

laser light, Fabreet al. were able

to measure what raction o the

incident cloud was refected, and

how many atoms were trans-

mitted. The refectivity o the

mirror could be controlled by in-

creasing the laser power.

Periodic mirrors are already

well known in optics, where they

are called distributed Bragg re-

fectors. Alternating layers o

high- and low-reractive-indexmaterials can trap photons in

cavities, to construct lasers, or

example, or guide light propaga-

tion, as in optical bres. The de-

velopment o distributed Bragg

refectors or matter waves will

aid the translation o these con-

cepts rom light to matter.

David Gevaux,

Nature Physics

Phys. Rev. Lett.doi: 10.1103/

PhysRevLett.107.230401 (2011)

PARTICLE PHYSICS

Spot the

dierenceneutr inOs Osc illate

that is, each o the three types

o neutrino (electron, muon

and tau) can evolve into one o

the others, a behavior that is

captured in a matrix o mixing

angles. This also brings the

possibility o CP violation in

the neutrino sector, comple-

menting that seen in the

mixing o quarks, which could

be spotted through a detectable

dierence in the oscillation

probabilities or neutrinos and

antineutrinos.

Discrepancies between neu-

trino and antineutrino data

have been noticed by some ex-

periments, notably MINOS and

MiniBooNE, which both use

neutrino beams generated at

Fermilab, in the United States.

K. Abe and colleagues have

now searched data collected or

atmospheric neutrinos over an

11-year period by the Super-Ka-miokande apparatus, located in

the Mozumi mine under Mount

Kamioka in Japan.

In Super-Kamiokandes huge

underground tank, lined with

photomultiplier tubes and

illed with 50,000 tons o water

Abe et al. sought evidence o

the disappearance o muon

neutrinos and muon antineu-

trinos as they oscillated into

the other particle types.

Through a challenging analysisthat allows or 120 sources o

systematic uncertainty, the au-

thors conclude that, as yet, the

mixing parameters or neu-

trinos and antineutrinos rom

atmospheric sources are en-

tirely consistent with each

other.

Alison Wright

Nature Physics


PhysRevLett.107.241801 (2011)

A view of the southern hemisphere of Mars.

HUBBLESPACETELESCOPE/NASA

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SENSORS

Photon counting

distributed temperature

sensing can be useul or moni-

toring structures such as build-

ings and pipelines. Michael

Tanner and colleagues rom Her-

iot-Watt University in the UK and

the National Institute o Stan-

dards and Technology (NIST) in

Colorado, USA, have now built a

distributed ber Raman sensor

that can simultaneously measure

absolute temperature at over 100

1.2-cm-spaced positions along a

single-mode optical ber. Al-

though distributed ber sensors

have been around or a while, theresearchers claim that previous

research ocused on using multi-

mode bers and avalanche photo-

diodes, which limited detection

wavelengths to around 800900

nm. In contrast, this latest work

uses pulses o 1,550 nm light and

measures the single-photon level

Raman backscattered signal

using superconducting nanowire

single-photon detectors. The re-

searchers used a time-o-fight ap-

proach to determine the tempera-ture prole along the ber. They

recorded temperature measure-

ments at various positions along

the ber with an uncertainty o

less than 3 K over a period o 1

minute. They hope that a 1-km-

range distributed sensor will be

possible in the near uture.

David Pile,

Nature Photonics

Appl. Phys. Lett.doi:

10.1063/1.3656702 (2011)

QUANTUM OPTICS

Coherent

photonconversionentangled phOtOns are key

elements o quantum inorma-

tion processing and communica-

tions technology such as

quantum key distribution. Un-

ortunately, current schemes or

achieving entangled photon gen-

eration are inecient because o

the probabilistic processes in-

volved. Now, Nathan Langord

and co-workers rom Austria,

UK, Canada and Japan have pro-

posed a deterministic process

called coherent photon conver-

sion that could be more suitable

or practical applications. The

key principle o coherent photon

conversion is the use o classi-

cally pumped nonlinearities to

induce coherent oscillations be-

tween dierent multi-excitation

states. The resulting approach

oers a new way to generate and

process quantum states or

quantum inormation processingtasks such as multiphoton entan-

glement and the realization o

optically switched quantum cir-

cuits. The researchers demon-

strated their approach by using a

our-color nonlinear process in a

standard commercial, polariza-

tion-maintaining photonic

crystal ber with a 532 nm

pulsed laser and a 710 nm diode

laser.

Noriaki Horiuchi,

Nature Photonics


TRAPPINg

A marriage ofatoms and ionsscientists frOm the Raman

Research Institute in India and

the Johannes Gutenberg Univer-

sity in Germany have unveiled a

device that can simultaneously

trap both ions and cold atoms.

The apparatus combines a linear

radiorequency Paul trap or ions

with a six-laser-beam magneto-

optical trap or atoms. Spatial

overlap between the traps allows

the investigation o ionatom in-

teractions at low temperatures.

The researchers cooled the

atoms by laser Doppler cooling

using light rom an amplied

homemade external-cavity diode

laser. They tested their design

with85Rb atoms and85Rb+ ions,

which were made by using two-

photon ionization to strip elec-

trons rom85Rb atoms. The re-

searchers say that the scheme

also lends itsel to any speciesthat can be laser-cooled in a

vapor cell, and that experiments

with multiple species may even

be possible.

Oliver Graydon

Nature Photonics

Appl. Phys. B doi: 10.1007/s00340-011-

4726-6 (2011)

PLASMONICS

Optical blackholealthOugh the use o transor-

mation optics and metamaterials

to create optical analogues o

black holes has already been sug

gested, experimental realization

o the required material struc-

tures remains a signicant

hurdle. Khachatur Nerkararyan

and co-workers rom Yerevan

State University in Armenia and

the University o Southern Den-

Optical ber.

HENRIKJONSSON/ISTOCKPHOTO

A conventional ion trap.MNOLf/WIKIMEDIACOMMONS

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mark have now suggested that

spherical metal suraces brought

into contact may provide an al-

ternative approach or investi-

gating optical black holes. Theresearchers showed that plas-

mons with an appropriate trajec-

tory in the gap between two

metal spheres (or between a

sphere and a planar surace) can

be concentrated into a black

hole around the point o struc-

tural contact. The team used an

eective-index approximation to

simpliy the problem, thereby re-

ducing the three-dimensional

problem down to two dimen-

sions. In one example, they con-

sidered a 100-m-radius gold

sphere in contact with a planar

surace and 800-nm-wavelength

light. The eect relies on the act

that reducing the gap width in-

creases the eective permittivity

experienced by the gap plas-

mons, thanks to an increasing

Coulomb attraction across the

gap. This increased eective per-

mittivity draws the light towards

the point o contact, which

thereore acts as an optical black

hole. The researchers hope thatthis conguration can be real-

ized in practice to allow the

table-top exploration o phe-

nomena such as Hawking

radiation.

David Pile,

Nature Photonics

Opt. Lett. doi: 10.1364/

OL.36.004311 (2011)

ELECTRON MICROSCOPY

MappingensembleselectrOn micrOscOpyis

routinely used to characterize

the structure o metal nanoparti-

cles, and with the help o elec-

tron energy-loss spectroscopy,

chemical maps with atomic reso-

lution can also be obtained. A

chemical map o a single particle

can, however, take hours to re-

cord. Thereore, acquiring a sta-

tistically signicant sample o a

system that contains nanoparti-

cles with a variety o dierent

compositions, such as a hetero-

geneous catalyst, is impractical.

David Muller, Zhongyi Liu and

colleagues at Cornell University,

General Motors and Florida In-

ternational University have now

shown that the improved elec-

tron optics o an aberration-cor-

rected electron microscope can

allow hundreds o platinumco-

balt nanoparticles to be chemi-cally mapped.

The US team used a scanning

transmission electron micro-

scope that can correct up to the

th-order o aberrations and al-

lows data to be collected around

a thousand times aster than on

a conventional microscope. With

the instrument, the platinum

cobalt nanoparticles which

are promising as a uel-cell cata-

lyst but are known to degrade

over time were mapped at var-ious stages o ageing in a proton-

exchange-membrane uel cell. By

mapping ensembles o nanopar-

ticles, the precise structure and

composition o the catalyst could

be linked to its bulk electro-

chemical perormance with sta-

tistical condence.

Owain Vaughan,


Nano Lett.doi: 10.1021/

nl203975u (2011)

SUPER-RESOLUTION IMAgINg

Acoustic help

the resOlving capabilities oar-eld optical imaging schemes

are limited by their inability to

collect rapidly decaying evanes-

cent waves, which contain de-

tailed spatial inormation. To

overcome this restriction, Leonid

Alekseyev, Evgenii Narimanov

and Jacob Khurgin have now pro-

posed a time-multiplexed ap-

proach or recovering evanescent

waves in the ar-eld. In their

scheme, the object to be imaged is

placed in the near-eld o an

acousto-optic modulator and illu-

minated with a plane wave rom a

light source. Waves scattered rom

the object strike a phonon grating

ormed by the acousto-optic mod-

ulator, thereby causing the eva-

nescent components to be shited

in both requency and transverse

wave vector. The researchers dis-

covered that or a suciently

large phonon wave vector, the ev-

anescent components with high

spatial requency can be con-

verted into propagating waves,which can then be collected and

imaged. Super-resolved nger-

printing and digital holography

are suggested as two example ap-

plications o this scheme. Simula-

tions show that mixing the re-

quency-shited elds with a reer-

ence wave can create a

high-spatial-requency beat note

photocurrent at the detector, and

that true super-resolved imaging

can be achieved when the reer-

ence signal is Bragg-shited. Al-though this scheme is particularly

suitable or super-resolution im-

aging at inrared and terahertz

wavelengths, the researchers say

that it might also be able to work

at optical requencies by replacing

the acousto-optic medium with a

moving nanostructured grating.

Rachel Won

Nature Photonics

Opt. Express doi: 10.1364/

OE.19.022350 (2011)

Electron microscope.

JACOMSTEPHENS/ISTOCKPHOTO

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SOLAR CELLS

Fano-enhanced

performanceQuantum cOherencebe-

tween competing energy-level

pathways is known to help opti-

mize photosynthesis and enable

phenomena such as lasing

without inversion. Researchers

rom Texas A&M University and

Princeton University in the USA

have now suggested that

quantum coherence could also

be used to enhance the peror-

mance o solar cells. One idea is

to split degenerate excited en-

ergy levels by exploiting tun-

neling between two adjacent

quantum dots. The two split en-ergy levels (known as an energy

level doublet) both couple to the

conduction state. Fano interer-

ence between the two pathways

minimizes unwanted radiative

transitions and helps to maxi-

mize the generated photocur-

rent. An alternative approach is

to create an energy level doublet

rom two lower-energy levels

and use Fano intererence to en-

hance the absorption o solar en-

ergy. Theoretical analysis o this

scheme suggests that the photo-

current and peak power o a pho

tovoltaic cell employing ully co-

herent Fano intererence couldbe improved by up to 50 percent

The researchers also suggest the

possibility to engineer the cell

such that the Fano intererence

is robust against environmental

decoherence. The challenge now

is or the research community to

realize such a cell in practice.

Oliver Graydon

Nature Photonics

Phys. Rev. A doi: 10.1103/

PhysRevA.83.053818 (2011)

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