Experimental work on entangled photon holes
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Transcript of Experimental work on entangled photon holes
Experimental work on entangled photon holes
T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson
UMBC
ICSSUR Olomouc, June 2009
Experimental work on entangled photon holes
T.B. Pittman, S.M. Hendrickson, J. Liang, and J.D. Franson
UMBC
ICSSUR Olomouc, June 2009
Linear Optics Quantum Computing,Zeno Gates
Entangled-Photon Holes
Outline
Entangled Photon holes?
Generation of these states by two-photon absorption quantum interference
Experimental observation of photon holes using quantum interference
Towards Bell’s inequality tests
Optical Entanglement
Entanglement of photon pairs: polarization momentum …. ….combinations of properties
We are investigating a new form of entanglement arises from the absence of photon pairs themselves correlated absences…. “Entangled photon holes”
Polarization entanglement from Type II PDC (Kwiat ‘95)
Creation of entangled photon holes can have macroscopic effects on two-photon absorption effects of entanglement can be observed with “classical detector”
This talk will focus instead on the basic concept and recent experimental work
What are entangled photon holes?
First, consider photon pairs from typical PDC scenario: Photons generated at same time, but that time is uncertain
superposition of these times entanglement
background in each beam is empty but uniform probability amplitude to find photon pair anywhere
parametricdown-conversion
What are entangled photon holes?
Now consider ideal two-photon absorption Photons annihilated at same time, but that time is uncertain
superposition of these times entanglement
Background in each beam is constant But uniform probability amplitude to find hole pair anywhere
Two-photonabsorption medium
weak coherentstate inputs
1
2
3
(3-level atoms)
1
2
3
1
2
3
(3-level atoms)
Consider two single-photon inputs
coin
c. ra
te
- 0 + (t1-t2)
coin
c. ra
te
- 0 + (t1-t2)
“holes” correlated in time, but could be generated at any time:
coherent superposition
time
ampl
itude
photon 1
photon 2
time
ampl
itude
photon 1
photon 2
PDC with narrowband pump
photon pair could be produced at any time
coherent superposition of these times
coin
c. ra
te
- 0 + (t1-t2)
coin
c. ra
te
- 0 + (t1-t2)
time
ampl
itude
photon 1
photon 2
time
ampl
itude
photon 1
photon 2
Photon pairs vs. Photon holes
Entangled photon holes: “negative image” of PDC
empty background photon pair anywhere
constant background hole pair anywhere
Ideal two-photon absorption?
Generation of entangled photon holes in this way requires strong two-photon absorption at the single-photon level
Very difficult to achieve (works in progress) example system: tapered optical fiber in atomic vapor
Can entangled photon holes be generated through quantum interference instead?
Yes
1
2
3
(3-level atoms)
1
2
3
1
2
3
(3-level atoms)
TPA in tapered optical fibers
“heat and pull”: sub-wavelength diameter wires evanescent field interacts with Rubidium vapor
evanescent field outside fiber
Rb atoms
Reduced mode volume beats optimal free-space focusing (for TPA)
optical fiber
Recent experiments with tapered optical fibers in Rb
gives ~106 improvement in TPA rateover focused beam
even this is way too small for observingTPA at single-photon levels!
H.You et.al. PRA 78, 053803 (2008)
taper: d ~ 450 nm(over L ~ 5 mm)
d ~ 125 m
Side note: nonlinear transmission through TOF
Rb atoms tend to accumulate on TOF Reduces transmission (scattering)
can be removed using optical beam propagating through the TOF probably LIAD & thermal effects
results in nonlinear transmission %
Nonlinear transmission
saturation spectroscopy
S.M. Hendrickson et.al. JOSA B 26, 267 (2009)S. Spillane et.al PRL 100, 233602 (2008)
Photon holes via quantum interference
Interference effect to suppress the probability P11 of finding one photon in each output mode?
weak coherent stateweak coherent state
?
Photon holes via quantum interference
mix with phase-locked PDC source at 50/50 BS
Interference effect to suppress the probability P11 of finding one photon in each output mode?
Note: TPA case: classical in nonlinearity quantum out
this case: classical in + quantum in interference quantum out
phase locked,
PDC source
weak coherent state
50/50 beam splitter
phase locked,
PDC source
weak coherent state
50/50 beam splitter
Photon holes via quantum interference
what is P11 ?phase locked,
PDC source
weak coherent state
50/50 beam splitter
phase locked,
PDC source
weak coherent state
50/50 beam splitter
If indistinguishable amps and = , destructive interference (P11 = 0) suppress any pairs from “splitting” at 50/50 leaves photon hole pairs in constant laser background
experimental challenge: how to phase-lock PDC & weak laser? answer: Koashi et.al. phase-coherence experiment (1994)
1,11,1~ 221,1 ie
due to 2-photon termof weak coherent state due to PDC pair
1,11,1~ 221,1 ie
due to 2-photon termof weak coherent state due to PDC pair
frequency-doubled laser (2) for PDC pump PDC pairs at fundamental () as weak coherent state MZ-like interferometer phase
Versatile method: many implementations possible…
Koashi et.al. PRA (1994) Kuzmich et.al. homodyned Bell-test PRL 85, 1349 (2000)
Resch et.al. two-photon switch PRL 87, 123603 (2001)
Lu and Ou, cw experiment PRL 88, 023601 (2002)
Photon holes experiment
stopstart
TACdata aq.
APD-2
APD-1
primarybeam splitter
mode-lockedlaser
SHGPDC
crystal
ND
delay
delay
filter
-platePBS
filters
“HOM” beam splitterlaserpick-off
PDC
laser
Photon holes experiment
stopstart
TACdata aq.
APD-2
APD-1
primarybeam splitter
mode-lockedlaser
SHGPDC
crystal
ND
delay
delay
filter
-platePBS
filters
“HOM” beam splitterlaserpick-off
PDC
laser
“HOM dip”V~99%
Photon holes experiment
stopstart
TACdata aq.
APD-2
APD-1
primarybeam splitter
mode-lockedlaser
SHGPDC
crystal
ND
delay
delay
filter
-platePBS
filters
“HOM” beam splitterlaserpick-off
PDC
laser
“HOM dip”V~99%
giant MZ interferometer(fiber and free-space)
key point: phase
step 1: calibration
0
500
1000
1500
2000
-20 0 20 400
500
1000
1500
2000
-20 0 20 40
weak laser only(76 MHz pulse train)
PDC only
relative delay (ns)
coin
cide
nce
coun
ts
matched two-photon amplitudes
coinc.countscoinc.counts
step 2: phase control
= 180o
= 0o
Visibility ~90%
coinc.countscoinc.counts
step 3: observation of photon holes
coinc.countscoinc.counts
relative delay (ns)
coin
cide
nce
coun
ts0
500
1000
1500
2000
-20 0 20 40
relative delay (ns)
coin
cide
nce
coun
ts0
500
1000
1500
2000
-20 0 20 400
500
1000
1500
2000
0
500
1000
1500
2000
-20 0 20 40
Probability of finding one photon in each beam is suppressed
Note: not completely eliminated. due to imperfect mode-matching
Pittman et.al. PRA 74, 041801R (2006)
Data summary
main result
laser only PDC only
Data summary
main result
laser only PDC onlyImportant: data collected shows existence of photon holes, but does not demonstrate entangled nature of state -- analogous to just measuring “photon pairs” in, say, Kwiat ’95 polarization experiments
additional measurements are required: -- Bell test with entangled photon holes
PDC sourceonly S1S2 and L1 L2 amplitudes
can be used to violate Bell’s ineq.
Bell’s inequality tests
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
basic idea: use “Franson interferometer”
2cos~ 212
cR
photon holes sourcePhotons never emitted at same timeonly S1L2 and L1S2 amplitudes
PDC sourceonly S1S2 and L1 L2 amplitudes
can be used to violate Bell’s ineq.
Bell’s inequality tests
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
basic idea: use “Franson interferometer”
2cos~ 212
cR
2cos~ 212
cR
photon holes sourcePhotons never emitted at same timeonly S1L2 and L1S2 amplitudes
PDC sourceonly S1S2 and L1 L2 amplitudes
can be used to violate Bell’s ineq.
Bell’s inequality tests
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
S
L
1
S
L
S
L
1
2
S
L
2
S
L
coinc.counts
basic idea: use “Franson interferometer”
2cos~ 212
cR
2cos~ 212
cR
Interpretation is difficult: detectors only register background photons -- photon holes suppress detection process in a nonlocal way
Time-bin entangled photon holes
Photon hole generation: relies on interference of independent sources short-pulsed lasers/narrowband filters for indistinguishability no cw “energy-time” type entanglement
this puts our Bell test exp’s into the “time-bin” regime (Gisin’s group) Experiments currently underway (4 stabilizations req’d)
Time-bin entangled photon holes
Photon hole generation: relies on interference of independent sources short-pulsed lasers/narrowband filters for indistinguishability no cw “energy-time” type entanglement
this puts our Bell test exp’s into the “time-bin” regime (Gisin’s group) Experiments currently underway (4 stabilizations req’d)
photon hole source
Summary and outlook
New form of entanglement entangled photon holes “negative image” of PDC
Generation via ideal TPA or quantum interference effects recent experiments
Many open questions: … quantum communications …
Some comments on photon hole data
Data looks similar to that typically obtained by splitting a conventional anti-bunched state But that kind of (two-beam) state is very different than photon hole
states of interest here
excitation pulse train
statistics of either beam resemble a coherent state splitting an antibunched beam
gives two antibunched states
50/50 beam splitter
laser 1
PDC
-lock-lock
50/50 beam splitter
laser 1
PDC
-lock-lock
>> also different than the (single-mode) states produced by “hole-burning” in Fock space: B. Basiea et.al. Phys. Lett A 240, 277 (1998)
>> and not the same as the two-mode single-photon states of the form |0,1> + | 1,0>
(HISTORICAL SIDE NOTE)
1st demo that required “Multi-photon” experimental conditions Ultra-fast pulsed-PDC and narrow-
band filters for indistinguishability now used for many experiments
Koashi et.al. PDC phase coherence PRA 50, R3605 (1994)
Bouwmeester et.al. Teleporation Nature 390, 575 (1997)
Rarity et.al. PDC & |>Philos. Trans. 355, 2567 (1997)
Fiber-based interferometer
HOM & primary beam splitters
PDC photons
HOM beam splitter
primarybeam splitter
weaklaser pulse
Rb TPA frequency-locking system
PBS /4
wavelength meter spectral analysis
narrowbandfilter
detector(SPCM or PIN)
fluorescencecollection
SM fiberMM fiber
778 nm input
aux. output beam Rb vapor cellin TC’d oven
f = 80 mm lenses
PBS /4
wavelength meter spectral analysis
narrowbandfilter
detector(SPCM or PIN)
fluorescencecollection
SM fiberMM fiber
778 nm input
aux. output beam Rb vapor cellin TC’d oven
f = 80 mm lenses
PBS /4
wavelength meter spectral analysis
narrowbandfilter
detector(SPCM or PIN)
fluorescencecollection
SM fiberMM fiber
778 nm input
aux. output beam Rb vapor cellin TC’d oven
f = 80 mm lenses
PBS /4
wavelength meter spectral analysis
narrowbandfilter
detector(SPCM or PIN)
fluorescencecollection
SM fiberMM fiber
778 nm input
aux. output beam Rb vapor cellin TC’d oven
f = 80 mm lenses
laser frequency scan (GHz)
fluor
. cou
nts
(arb
)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Doppler-free peaks
Doppler-broadened peaks ~ 1 GHz
PDC lock
laser frequency scan (GHz)
fluor
. cou
nts
(arb
)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 laser frequency scan (GHz)
fluor
. cou
nts
(arb
)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Doppler-free peaks
Doppler-broadened peaks ~ 1 GHz
PDC lock
780 nm
778 nm
778 nm
420 nm
5 2D5/2
6 2P3/2
5 2S1/2
5 2P3/2
~ 2 nm
optimal PDCbandwidth ~ 3 nm
780 nm
778 nm
778 nm
420 nm
5 2D5/2
6 2P3/2
5 2S1/2
5 2P3/2
~ 2 nm
780 nm
778 nm
778 nm
420 nm
5 2D5/2
6 2P3/2
5 2S1/2
5 2P3/2
~ 2 nm
optimal PDCbandwidth ~ 3 nm