La lumière in vivo

1

1

La lumière La lumière in vivoin vivo

Igor DotsenkoIgor Dotsenko

Chaire de physique quantique,Chaire de physique quantique,

Collège de FranceCollège de France

Journée de l'Institut de Biologie du Collège de FranceJournée de l'Institut de Biologie du Collège de FranceParis, 24 novembre 2009Paris, 24 novembre 2009

Journée de l'Institut de Biologie, 24/11/09 2

Light for exploring the nature

ScienceScience: : From studies of biological cells From studies of biological cells

to distant galaxies the light is the fist tool to start with.to distant galaxies the light is the fist tool to start with.

Everyday life: Most information on our environment Everyday life: Most information on our environment

we obtain through light we obtain through light (about 80%). (about 80%).


Object of investigation

For many centuries, light itself was For many centuries, light itself was

an object of interest and investigation for scientists.an object of interest and investigation for scientists.

I. Newton, light dispersionI. Newton, light dispersion T. Young, light interferenceT. Young, light interference

H. Fizeau and L. Foucault, H. Fizeau and L. Foucault,

speed of lightspeed of light

Classical properties: electromagnetic wave Classical properties: electromagnetic wave

with speed with speed cc, frequency , frequency , wavelength , wavelength , etc., etc.


The story of light is not over:The story of light is not over:

Light is still very intriguing and Light is still very intriguing and

fascinating object to explore !!!fascinating object to explore !!!

The story of light is not over:The story of light is not over:

Light is still very intriguing and Light is still very intriguing and

fascinating object to explore !!!fascinating object to explore !!!

Photon - intrinsically "quantum" state of light

Non-classical, quantized photon-number states like:Non-classical, quantized photon-number states like:

|exactly |exactly nn photons photons

The smallest bit of light with The smallest bit of light with

unit energy and momentum:unit energy and momentum:

Quantum superposition allows more "exotic" states likeQuantum superposition allows more "exotic" states like

(( |exactly |exactly nn photons photons ++ |exactly |exactly kk photons photons ))

No wayNo way to illustrate and understand such to illustrate and understand such

superposition states with superposition states with classical intuitionclassical intuition ! !

or like:or like:

(( |all photons fly |all photons fly leftleft ++ |all photons fly |all photons fly rightright ))


Catching a photon

Several ways to tackle the question Several ways to tackle the question "How things work"How things work?"?"

1.1.

observe and observe and

wonderwonder

3.3.

catch and have a catch and have a

closer look !closer look !

2.2.

disturb and followdisturb and follow


Catching a photon

Fabry-Perot resonatorFabry-Perot resonator

mir

ror

mir

ror

Requirements: Requirements: perfectperfect reflection off the mirrors !!! reflection off the mirrors !!!

((nono absorption, absorption, nono transmission, transmission, nono scattering) scattering)


Microwave superconducting cavity: Storage box for photons

5 cm5 cm

- a light travel distance of 39 000 a light travel distance of 39 000 km km (one full turn around the (one full turn around the Earth)Earth)

-1.4 billion bounces off the mirrors1.4 billion bounces off the mirrors

2.8 cm2.8 cm

TTlightlight = 130 ms = 130 ms


Study light in vivo ?

But, (usually) to But, (usually) to seesee or or exploreexplore light means to light means to absorbabsorb it, it,

e.g.e.g. by an eye retina or a CCD chip! by an eye retina or a CCD chip!

Can we use a Can we use a transparenttransparent (like glass) probe? (like glass) probe?

YesYes, use giant (Rydberg) atoms , use giant (Rydberg) atoms

flying one-by-one flying one-by-one across the field.across the field.1/4 1/4 mm


Rydberg atoms

Rydberg states:Rydberg states:uniform electron distributionuniform electron distribution(i.e. no phase information)(i.e. no phase information)

(n+1) (n+1) /2 = 2/2 = 2rr

n n /2 = 2/2 = 2rr

number of oscillations number of oscillations

(principle quantum number)(principle quantum number)

Superposition of two orbits:Superposition of two orbits:induced dipole rotates induced dipole rotates

at atomic frequency at atomic frequency atomatom

Information on Information on atomatom

is encoded in is encoded in the dipole phase the dipole phase

Information on Information on atomatom

is encoded in is encoded in the dipole phase the dipole phase


¢ e / n

¢ g / ¡ n

Off-resonant interaction

lightatom

Energy conservation Energy conservation the field is preserved the field is preserved Atom-field interaction modifies Atom-field interaction modifies atomatom proportional to proportional to nn Phase shift of the atomic dipole (relative to free Phase shift of the atomic dipole (relative to free

atom)atom)

Phase shift per photon (depends on interaction strength)Phase shift per photon (depends on interaction strength)


Phase measurement: Atomic clock

1. Trigger of the atom 1. Trigger of the atom clock:clock:resonant pulseresonant pulse

no photons

no photons

1 photon1 photon

Atomic state (Atomic state (ee//gg) is correlated with number of photons ) is correlated with number of photons ((11//00))

2. Dephasing of the clock:2. Dephasing of the clock:interaction with the cavity interaction with the cavity fieldfield3. Measurement of the clock: 3. Measurement of the clock: second pulse & state detectionsecond pulse & state detection

Phase shift per photon adjusted to Phase shift per photon adjusted to


Birth, life and death of a photon

time [s] time [s]

atom

sat

oms

phot

on

phot

on

num

ber

num

ber


Birth, life and death of a photon

"Warm" cavity excites a thermal photon "Warm" cavity excites a thermal photon (black body radiation):(black body radiation):

time [s] time [s]

atom

sat

oms

phot

on

phot

on

num

ber

num

ber

((i.e.i.e. 5% of time there is one photon; 5% of time there is one photon; from Planck's law)from Planck's law)


Larger number of photons

Dephasing per photon Dephasing per photon 0 0 < <

for instance, for instance, 0 0 = =

Distinguish up to 7 photonsDistinguish up to 7 photons

n n = 0= 0

n n = 1= 1

n n = 2= 2n n = 3= 3

n n = 4= 4

n n = 5= 5

n n = 6= 6 n n = 7= 7

with

pro

ba

bili

ty

with

pro

ba

bili

ty

de

pe

nd

ing

on

d

ep

en

din

g o

n

(( n)n)

Measure dipole orientation with many (Measure dipole orientation with many (~~50) atoms50) atoms


Seeing quantum jumps of light

Repeatability Repeatability of QND of QND measurementmeasurement

Random projectionRandom projection onto one of onto one of nn valuesvalues

Quantum jumpsQuantum jumps between between discrete values of discrete values of nn: damping of the : damping of the field caught in the actfield caught in the act

Ph

oto

n n

umbe

r, n

Quantum non-demolition measurement: Light Quantum non-demolition measurement: Light in vivoin vivo

Initial stateInitial state is classical electro-magnetic field injected is classical electro-magnetic field injected from from a usual microwave source (number of photons is not a usual microwave source (number of photons is not defined !)defined !)


Perspectives: Non-local light

Cavity 1Cavity 1 Cavity 2Cavity 2

Study non-local states, Study non-local states, e.g.e.g.::||all photons in Cavity all photons in Cavity 1,1, not in not in 22 ++ ||all photons in Cavity all photons in Cavity 2,2, not in not in 11

What are their What are their propertiesproperties??

Why Why not observednot observed in our classical "macroscopic" world? in our classical "macroscopic" world?

Where is the transition from Where is the transition from quantumquantum to to classicalclassical??


The cavity QED team

Julien Bernu Julien Bernu ((→ → Canberra)Canberra)

Christine GuerlinChristine Guerlin ((→ Zurich→ Zurich))

Samuel Deléglise Samuel Deléglise ((→ Munchen→ Munchen))

Clément SayrinClément Sayrin

Xingxing ZhouXingxing Zhou

Bruno PeaudecerfBruno Peaudecerf

Michel BruneMichel Brune

Jean-Michel RaimondJean-Michel Raimond

Serge HarocheSerge Haroche

Igor Dotsenko Igor Dotsenko

Sébastien Gleyzes Sébastien Gleyzes

La lumière in vivo

Documents

Transcript of La lumière in vivo