Schrödinger’s Rainbow:
The Renaissance in Quantum
Optical Interferometry
Jonathan P. Dowling
Quantum Science & Technologies (QST) Group
Hearne Institute for Theoretical Physics
Louisiana State University
http://quantum.phys.lsu.edu
Table of Contents
• Quantum Technologies
• Schrödinger’s Cat and All That
• Quantum Light—Over the Rainbow
• Putting Entangled Light to Work
• The Yellow-Brick Roadmap
Quantum Technology: The Second Quantum Revolution
JP Dowling & GJ Milburn, Phil. Transactions of the Royal Soc. of London
Ion Traps
Cavity QED
Linear Optics
Quantum
Optics
Quantum Bose-Einstein
Atomics Atomic Coherence
Quantum
Ion Traps
Information
Processing
Coherent
Quantum
Electronics
Superconductors
Excitons
Spintronics
Quantum
Mechanical
Systems
Pendulums
Cantilevers
Phonons
Schrödinger’s Cat and All That
Schrödinger’s Cat Revisited
Quantum Kitty Review
A sealed and insulated box (A) contains a radioactive
source (B) which has a 50% chance during the course of
the "experiment" of triggering Geiger counter (C) which
activates a mechanism (D) causing a hammer to smash a
flask of prussic acid (E) and killing the cat (F).
An observer (G) must open the box in order to collapse
the state vector of the system into one of the two possible
states. A second observer (H) may be needed to collapse
the state vector of the larger system containing the first
observer (G) and the apparatus (A-F). And so on ...
Paradox? What Paradox!?
(1.) The State of the Cat is “Entangled” with That of the Atom.
(2.) The Cat is in a Simultaneous Superposition of Dead & Alive.
(3.) Observers are Required to “Collapse” the Cat to Dead or Alive
Quantum Entanglement
“Quantum entanglement is the characteristic trait of quantum
mechanics, the one that enforces its entire departure from
classical lines of thought.”
— Erwin Schrödinger
Conservation of Classical
Angular Momentum
A
Conservation of Quantum Spin
David Bohm
A
Entangled
B
Einstein, Podolsky, Rosen (EPR) Paradox
Albert Einstein
Boris Podolsky
Nathan Rosen
“If, without in any way disturbing a system, we can predict with
certainty ... the value of a physical quantity, then there exists an
element of physical reality corresponding to this physical
quantity."
Hidden Variable Theory
+
A
B
A
Can the Spooky, Action-at-a-distance Predictions
(Entanglement) of Quantum Mechanics…
B
+
A
B
A
…Be Replaced by Some Sort of Local, Statistical,
Classical (Hidden Variable) Theory?
B
NO!—Bell’s Inequality
John Bell
The physical predictions of quantum theory disagree
with those of any local (classical) hidden-variable theory!
Clauser (1978) & Aspect (1982) Experiments
Two-Photon
Atomic
Decay
H
V
A
B
V
H
Alain Aspect
H
A
V
B
+ V
A
H
B
John Clauser
V= Vertical Polarization
H = Horizontal Polarization
Quantum Light—Over the Rainbow
Parametric Downconversion: Type I
Parametric Downconversion: Type I
Photon Pairs
Signal B
UV
Pump
Idler A
Type I
Degenerate (Entangled) Case: ws=wi
w s , j s , ks
A
wi, ji, ks
B
+ w i , j i , ki
A
w s , js , ks
B
Parametric Downconversion: Type I
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Parametric Downconversion: Type II
Degenerate (Entangled) Case: ws=wi
H
A
V
B
+ V
A
H
B
B
A
QuickTime™ and a
Animation decompressor
are needed to see this picture.
Putting Entangled Light to Work
Tests of Bell’s Inequalities at Innsbruck
Type II Downcoversion
Anton Zeilinger
Alice
Bob
Quantum Teleportation
Teleportation Experiment at Innsbruck
EPR Source
Bell State Analysis
Experiment
NIST Heralded Photon Absolute Light Source
Output characteristics :
photon #
photon timing
wavelength
direction
polarization
 known
 known
 known
 known
 known
Alan Migdall
Detector Quantum Efficiency Scheme
Detector to be Calibrated
w1
COUNTER
COINC
COUNTER
N
w0
PARAMETRIC
CRYSTAL
Absolute
Quantum
Efficiency
w2
COUNTER
Trigger or “Herald” Detector
N1 = 1 N
N2 = 2 N
1 =NC/ N2
No External Standards Needed!
NC= 1 2 N
Characterizing Two-Photon Entanglement
Any two-photon
tomography requires 16
of these measurements.
V-polarized
(from #2)
#2
Kwiat Super-Bright Source
Examples
Arm 1
H
H
D
Arm 2
V
R
D
Detector
HWP PBS
QWP
This setup allows
measurement of an
arbitrary polarization
state in each arm.
Black Box
Generates arbitrary
Entangled States
QWP
HWP
PBS
Detector
Paul Kwiat
U. Illinois
Characterization of Entangled States
11
0.8
0.8
Maximally-Entangled
Mixed States
0.6
0.6
Werner States
0.4
0.4
0.2
0.2
0
0
0.1
0.2
0.2
0.3
0.4
0.4
0.5
0.6
0.6
0.7
0.8
0.8
0.9
11
Quantum Cryptography at University of Geneva
System Under Lake Geneva
Bob and “Charly” Share Random Crypto Key
Nicolas Gisin
New York Times
ORIGIN OF THE LITHO EFFECT
The Hong-Ou-Mandel
Effect
SHOMI FOR N=2
Parametric
Downcoversion
Phase Shifter
A
j
1
A
1B
0
A
2
B
+ 2
A
0
C
Coincidence
Counter
B
D
2
B
phase oscillates twice as fast
0
A
2
B
+ 2
2
A
0
B
Leonard Mandel
0
A
2
2ij
B
+e 2
2
A
0
B
Quantum Optical Lithography
Quantum Peak
Is Narrower and
Spacing is HALVED!
D
2
1.5
Classical One-Photon Absorption —
Classical Two-Photon Absorption —
Quantum Two-Photon Absorption —
1
0.5
-p
0
p
j
Displacement Measurements and Gravity Waves
xclassical   , xshotnoise 

N
, x Heisenberg 

N
Image of the wave plate
plane with waist=300m
33cm
coherent
beam
3.3cm
R=0.92
0.08
+ 0.92
wave plate
lens
f=3cm
squeezed vacuum : OPA
Hans Bachor
Australian National University
Quantum Clock Synchronization
Entangled Photons Can Synchronize Past the Turbulent Atmosphere!
Seth
Lloyd
MIT
A
B
Quantum Computing
Entangled Photons are a Resource for Scalable Quantum Computation!
E. Knill, R. Laflamme and
G. Milburn, Nature 409, 46, (2001)
Quantum Controlled-NOT Gate
using and Entangled-Light
Source, Beam Splitters, and
Detectors.
Gerard
Milburn
University
Of
Queensland
The Yellow-Brick Roadmap
Imaging
Communications
Metrology
Clock Synchronization
Sensors
Computing