indistinguishability of emitted photons from a semiconductor quantum dot in a micropillar cavity s....
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Indistinguishability of emitted photons from a semiconductor quantum dot in a micropillar cavity
S. Varoutsis
LPN Marcoussis
S. Laurent, E. Viasnoff, P. Kramper & M. GallardL. Le Gratiet, C. Mériadec, L. FerlazzoI. Sagnes, A. Lemaître, I. Robert-Philip, I. Abram
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Motivation Production of indistinguishable single photons
Toolbox for quantum optics experiments
Linear optics quantum computation
Photon-basedtwo-qubit gates
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Spectroscopy of single quantum dots
Sharp spectral lines at low temperature (< 30 eV)
Dephasing mechanisms (phonon, electrostatic)
“Artificial”atoms
InAs
Pumping on an excited state of the exciton : one e-h pair
Spectral filtering of the X line
Emission of single photons
GaAs
InAs
EGaAs
Wetting layer
Dot
900 910 920 930 940 950 960
200
400
600
800
1000
1200
1400
Inte
ns
ity
(a
rb.
un
its
)
Wavelength (nm)
0
Laser at 888nmT ~4K
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Generation of single photons
1 photon
StartDetector
StopDetector
50/50 Beamsplitter
T ~ 12.2 ns
2T 3T 3TT T
Start
Stop
0 T 2T 3T 4T
Nb
of
coi
ncid
ence
s
Delay t1
2
3
-20 -10 0 10 20
0,0
0,2
0,4
0,6
0,8
1,0
g(2) (t
)
Delay t (ns)
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Characteristics
Same polarization mode Same spatial mode Same spectral-temporal mode
Purest state of light
Pump pulse Pump pulse Pump pulse
time
Negligible jitter (relax ~10 ps) compared with pulse duration
No phase diffusion (T2) during the pulse duration
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Key parameters :
Indistinguishable Photons
For indistinguishable photons : T2 = 2 T1
t T1 ~ 1.2 ns
Lifetime : T1Coherence time :T2
Dephasing (phonons, electrostatic...)
Pure dephasing time T2*
T2 = 1/T2* + 1/2T1
1~ 300 ps
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons - T1
shortening Cavity effects (Purcell)
Cavity Quantum Electrodynamics (CQED)
We use an isolated emitter
X transition of a single QD
We modifythe EM environment
EM modes of a microcavity
Control of the interaction
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons - T1
shortening Cavity effects (Purcell)
F = = + 3 Q 0
3
0 42 V n3 0
Enhanced spontaneous emission into the cavity mode
Leakage spontaneous emission into free space
0
20
40
60
80
100
120
10
102
103
104
0 1 2 3 4 5 6 7 8 90 1 2 3 4 5 6 7 8 9
Q F
Diameter (m)
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons
│11> │12> t2 │13> │14> - r2 │13> │14> + rt │23> │04> - rt │03> │24>
│11> │02> r │13> │04> + t │03> │14>
│01> │12> t │13> │04> - r │03> │14>
A single photon on a beamsplitter
A single photon on each input arm of a beamsplitter
Both photons go the same way : «coalescence» into a two-photon state
1
2
3
4
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Experimental set-up
Time-interval counter
Spectro--meter
Sample
Stop
Start
2 ns
Spectro--meter
2 ns
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Experimental set-up
Photon 2
Photon 1
4 nsPhoton 1
Photon 2
2 nsPhoton 2
Photon 1
Peak at t=0(Long-Short)
Peak at t=4 ns(Short-Long)
Peak at t=2 ns
(Long-Long orShort-Short)
0 2 4-2-4 t (ns)
Number of events
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Experimental set-up
For indistinguishable photons
+
0 2 4-2-4 t (ns)
Number of events
Photon 1
Photon 2
Peak at t=0(Long-Short)
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons
Num
ber
of e
vent
s
Strongly reduced probability (ideally 0) of simultaneous detection of two photons (i.e. one on each output arm)
The photons coalesce two-photon state
-20 -10 0 10 200
100
200
300
400
500
600
Photon separation t (ns)
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Direct measurement of T1 and T2
-40 0 40 80 120 1600,0
0,2
0,4
0,6
0,8
Vis
ibili
ty
Time (ps)
1,0
T2 ~ 100ps
-200 0 200 400 600 800
0
1000
2000
3000
4000
5000
6000
Inte
nsi
ty (
arb
. unit
s)
Time (ps)
T1 ~ 90ps
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Mandel dip
212
2
1
*2
2
1
2)2(
2221
21)( TTT ee
T
Te
T
T
RT
RTg
T1 ~ 90ps T2 ~ 100ps and T2* ~ 225ps F ~15 & Coalescence efficiency ~ 55%
Photon 2
Photon 1
J. Bylander, I. Robert-Philip, and I. Abram, Eur. Phys. J. D 22, (2003) 295-301
-300 -200 -100 0 100 200 3000,0
0,2
0,4
0,6
0,8
1,0
g(2
) ()
Time delay (ps)
Theoretical prediction for: T1 = 90ps and T2 = 100ps Experimental Data
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Indistinguishable Photons Mandel dip
T1 ~ 60 - 110 ps T2* ~ 200 - 660 ps
F ~15-25Best coalescence efficiency ~ 76%
-400 -200 0 200 4000,0
0,2
0,4
0,6
0,8
1,0
Delay (ps)
g(2
) ()
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Resonant condition of Purcell effect
0 260
80
100
120
140
-4 -2 0 2 40
4
8
12
16
20
24Li
feti
me (
ps)
Pu
rcell Fa
ctor
Detuning (Angstroms)
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Temperature dependence
3.3 2.9 2.8 0 -2.2Detuning (Å)
g(2
)(0)
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 500
100
200
300
400
500
Chara
cteri
stic
T2*
T1
g(2
)(0)
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 500
100
200
300
400
500
Chara
cteri
stic
tim
es
(ps)
Temperature (K)
T2*
T1
LABORATOIRE DE PHOTONIQUE ET DE NANOSTRUCTURES
Conclusions
Generation of indistinguishable single photons Toolbox for quantum optics experiments Engineering of nanosources for photon-based quantum
information processing
Future prospect : Generation of entangled photons to implement more
sophisticated functionalities of quantum information processing (teleportation, quantum logic...)