Stabilization of nonclassical states of one- and two-mode ...
Nonclassical Light
Transcript of Nonclassical Light
Nonclassical Light
Slide presentation accompanying the
Lecture by Roman SchnabelWinter Semester 2004/2005
Universität HannoverInstitut für Atom- und MolekülphysikZentrum für GravitationsphysikCallinstr. 3830167 HannoverGermany
Roman. [email protected]
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Nonclassical LightI. Introduction
1. The Measurement Process and Heisenbergs Uncertainty Relation2. The Einstein-Podolski-Rosen–Paradox and Bells Inequality
II. Single Photons and Discrete Variables3. Experimental Tests of Bells Inequality (The Aspect-Experiment)4. Maximally and Non-Maximally Entangled States
(Bell- and Hardy-states, Schrödinger Cat States)5. More Experiments with Nonclassical Photon States (A)6. More Experiments with Nonclassical Photon States (B)
III. Beams of Light and Continuous Variables7. Squeezing from 2nd and 3rd Order Nonlinearities 8. OPO/OPA Squeezing Experiments in the CW Laser Regime (A)9. OPO/OPA Squeezing Experiments in the CW Laser Regime (B)
10. Polarization Squeezing and Spatial Mode Squeezing11. Entangled Laser Beams 12. Kerr Squeezing Experiments in the Pulsed Laser Regime
IV. Applications of Nonclassical Light (Beams and Single Photons)13. Quantum-Non-Demolition, Teleportation and Entanglement Swapping 14. Loop-Hole Free Bell Test and Quantum Cryptography15. Outlook: Nonclassical Interferometry
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I. Introduction1. The Measurement Process andHeisenbergs Uncertainty Relation
TopicsInterpretations of Quantum TheoryMeasurement process DecoherenceGeneralized Uncertainty Principle
Literature (today)• David J. Griffiths, Introduction to Quantum Mechanics• W. H. Zurek, Rev. Mod. Phys. 75, 715 (2003),
Decoherence, einselection, and the quantum origins of the classicalGeneral Textbook Literature (next weeks)• H.-A. Bachor and T. C. Ralph,
A Guide to experiments in Quantum Optics, 2nd edition• D. F. Walls and G. J. Milburn, Quantum Optics
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I. 1. The Measurement Process
The Copenhagen Interpretation (proposed by Bohr)Quantum and classical world are separated from each other by a boundary, each world are governed by its own set of laws. The concept of superposition only exists in the quantum world, where we need to distinguish two types of physical processes: the ordinary ones, in which the wave function evolves smoothly under the Schrödinger Equation and measurement processes in which the wave function suddenly collapses.Problem 1: Indeterminacy reveals a lack of physical reality before a collapse Problem 2: What is the compelling reason for the quantum-classical boundary and two sets of laws?Problem 3: Ultimately also the classical world is made from “quantum stuff”. How does the classical evolve from the quantum world?
The Many-Worlds Interpretation (proposed by Everett)The whole universe is represented by a unitarily evolving state vector which is a gigantic superposition to accommodate all the alternatives. It does not suffer from the sudden collapse of the wave function because all alternatives do still exist.Problem 1: The intuitively obvious “conservation law” is violatedProblem 2: Why are the laws of classical physics so stable in this permanently splitting universe we live in?
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I. 1. The Measurement Process
Some Answers to some of the questions: Decoherence [Zurek03]Since there is no need for a “collapse” in a universe seen from outside, the collapse and the appearance of the classical should be described in a universe made from interacting quantum systems seen from within. Now environment can destroy coherence of quantum states of a system -decoherence. The point is that decoherence does not affect all superpositions equally. There are some states (pointer states) which are robust against interaction with environment. These states define classical states. It turns out that decoherence goes hand in hand with a spreading of information about the system through the environment which is ultimately responsible for the emergence of “objective reality”. The objective reality of a state can be quantified by the redundancy with which it is recorded throughout the universe.
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I. Introduction2. The EPR – Paradox and Bells Inequality
TopicsThe Einstein-Podolski-Rosen – ParadoxDerivation of Bell´s InequalityNon-Locality
Literature• A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935), Can quantum
mechanical description of physical reality be considered complete? • L. Hardy, Contemporary Physics, 39, 419 (1998), Spooky action at a distance in
quantum mechanics.• N. D. Mermin, Physics Today, 38 (April 1985), Is the moon there when nobody
looks?• R. Penrose, Phil. Trans. R. Soc. Lond. A 356, 1927 (1998), Quantum computation,
entanglement and state reduction.**(as an example for strange interpretations of quantum mechanics).
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I. 2. The EPR–Paradox and Bells Inequality
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I. 2. The EPR–Paradox and Bells Inequality
Weak electro-magnetic signal(detected signal is about one photon)
Questions:What is the wavelength of thesignal?What is the arrival time (position) of the signal (photon)?
What type of experiment give answers?
What is the consequence of the quanta (photons)?
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σ A2σ B
2 ≥12i
ˆ A , ˆ B [ ]⎛ ⎝ ⎜
⎞ ⎠ ⎟
2 ˆ A = x, ˆ B = p =
h
i∂∂x
Generalized Uncertainty Principle
Regarding the quantum mechanical wave function the wavelength of Ψ is related to the momentum of the particle by the de Broglie formula:
Thus a spread in wavelength corresponds to a spread in momentum:
⇒ ˆ A , ˆ B [ ] = ih
⇒ σ xσ P ≥h
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I. 2. The EPR–Paradox and Bells Inequality
Position – momentum uncertainty of a particle
p = 2πh /λ
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. Introduction2. The EPR – Paradox and Bells Inequality
..
I. 2. The EPR–Paradox and Bells Inequality
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March 1947:``I cannot seriously believe in [quantum theory] because it cannot be reconciled with the idea that physics should represent a reality in time and space, free from spooky actions at a distance.´´
March 1948:``That which really exists in B should … not depend on what kind of measurement is carried out in part of space A; it should also be independent of whether or not any measurement at all is carried out in space A.´´
Do you believe that the moon exists only when you look at it?
Albert Einstein 1930 Max Born ~1930
I. 2. The EPR–Paradox and Bells Inequality
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John S. Bell
John S. Bell in 1964:
It makes an observable difference if the particle had a precise (though unknown) position prior to the measurement or not.
I. 2. The EPR–Paradox and Bells Inequality
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II. Photons 3. Experimental Tests of Bells Inequality
TopicsThe Aspect-ExperimentLoopholes in experimental tests of Bells inequality
(proves of non-locality?)
Literature• A. Aspect, P. Grangier and G. Roger, Phys. Rev. Lett. 49, 91 (1982).• J. F. Clauser and A. Shimony, Rep. Prog. Phys 41, 1881 (1978).• J. F. Clauser, M. A. Horne, A. Shimony and R. A. Holt,
Phys. Rev. Lett. 23, 880 (1969).• A. Aspect, P. Grangier and G. Roger, Phys. Rev. Lett. 47, 460 (1981).• A. Aspect, J. Dalibard and G. Roger, Phys. Rev. Lett. 49, 1804 (1982).• A. Zeilinger, Phys. Lett A 118, 1 (1986).• E. Santos, Phys. Rev. A 46, 3646 (1992).
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E θ;φ( )= P++ θ;φ( )+ P−− θ;φ( )− P+− θ;φ( )− P−+ θ;φ( )= cos 2θ − 2φ( )
Snon− local = E 0°;22,5°( )+ E 45°;22,5°( )+ E 45°;67,5°( )− E 0°;67,5°( )= 2 2
Slocal ≤ 2
Ψ =12
VV + HH( )
II. 3. Experimental Tests of Bells Inequality
Source of entangled pairsθ φ
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II. Photons 4. Maximally and
Non-Maximally Entangled StatesTopicsExperiments with maximally and non-maximally
entangled states (Bell- and Hardy-states)Defining properties of entanglementCharacterization of entangled and separable statesQuantum CakesSchrödinger Cat states
Literature• P. G. Kwiat, K. Mattle, H. Weinfurter, and A. Zeilinger
Phys. Rev. Lett. 75, 4227 (1995), New high-intensity source of polarization-entangled photon pairs.
• A. G. White, D. F. V. James, P. H. Eberhard and P. G. Kwiat, Phys. Rev. Lett. 83, 3103 (1999), Non-maximally entangled states: Production, Characterization, and Utilization.
• D. Bruß, J. Math. Phys. 43, 4237 (2002),• L. Hardy, Phys. Rev. Lett. 71, 1665 (1993),• P. G. Kwiat and L. Hardy, Am. J. Phys. 68, 33 (2000),• P. Grangier, Nature 419, 577 (2002), Single photons stick together.
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Ψ± =12
↔b ± b↔( )
φ ± =12
bb ± ↔↔( )
Generation of Maximally Entangled States
*
II. 4. Maximally and Non-Maximally …
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Generation of Maximally Entangled StatesII. 4. Maximally and Non-Maximally …
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Generation of Maximally Entangled StatesII. 4. Maximally and Non-Maximally …
Violation of Bells Inequality by up to ~100 standard deviations
P. G. Kwiat, K. Mattle, H. Weinfurter, and A. Zeilinger, Phys. Rev. Lett. 75, 4227 (1995)
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θ φ
II. 3. Experimental Tests of Bells Inequality
Source of entangled pairs
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Non- Maximally Entangled States and Non-Locality
A. G. White, D. F. V. James, P. H. Eberhard and P. G. Kwiat, Phys. Rev. Lett. 83, 3103 (1999)
II. 4. Maximally and Non-Maximally …
ψ = ↔↔ + ε bb( )/ 1+ ε2 , ε = tanχ
αβ
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Non- Maximally Entangled States and Non-LocalityII. 4. Maximally and Non-Maximally …
ε = 0.47α = 55.6° ⇒β = 72.1°
pexp(α,−α) ≈ 0
pexp(α ⊥ ,−β) ≈ 0
pexp(β,−α ⊥ ) ≈ 0
pexp(β,−β)
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P. G. Kwiat and L. Hardy, Am. J. Phys. 68, 33 (2000)
II. 4. Maximally and Non-Maximally …
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Ψ cat =
12
b1b 2b 3 ...bN + ↔1↔2↔3 ...↔N( )= " live cat" + "dead cat"
II. 4. Maximally and Non-Maximally …
Mesoscopic Schrödinger Cat States
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Quantum Interference at the Beam-splitter
II. 4. Maximally and Non-Maximally …
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II. Photons 5. More Experiments with Nonclassical
Photon States (A)
TopicsThe intensity correlation functionExperiments with
- photon pairs - Bell test with space like separation- single photons on demand
Literature• H.-A. Bachor and T.C. Ralph, A Guide to Experiments in Quantum Optics,
Wiley, 2nd edition, 2004.• G. Weihs, T. Jennewein, C. Simon, H. Weinfurter, and A. Zeilinger
Phys. Rev. Lett. 81, 5039 (1998),Violation of Bell’s Inequality under strict Einstein locality conditions.
• B. Lounis and W. E. Moerner, Nature 407, 491 (2000),Single photons on demand from a single molecule at room temperature.
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Photon Pairs - Bell Test with Space like separation
II. 5. More Experiments with nonclassical …
G. Weihs et al., Phys. Rev. Lett. 81, 5039 (1998)
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Photon Pairs - Bell Test with Space like separation
II. 5. More Experiments with nonclassical …
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Photon Statistics – A Simple Experiment
II. 5. More Experiments with nonclassical …
1 2 3 t(ms)
Signal
Single Photon Detector
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Photon Statistics – A Simple Experiment
II. 5. More Experiments with nonclassical …
Poissonian distribution, of expectation value k=4
k
enkknP k
n
=
= −
2
!),(
σ
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II. Photons 6. More Experiments with Nonclassical
Photon States (B)TopicsSingle photons from single molecules,
quantum dots and single-ion optical-cavity systems
Single photon detectors
Literature• B. Lounis and W. E. Moerner, Nature 407, 491 (2000).
Single photons on demand from a single molecule at room temperature. • C. Santori, D. Fattal, J. Vuckoviv, G. S. Solomon, and Y. Yamamoto, Nature 419,
594 (2002), Indistinguishable photons from a single-photon device.• M. Keller, B. Lange, K. Hayasaka, W. Lange, and H. Walter, Nature 431, 1075
(2004), Continuous generation of single photons with controlled waveform in a ion-trap cavity system.
• S. Takeuchi, J. Kim, Y. Yamamoto, and H. H. Hogue, Appl. Phys. Lett. 74, 1063 (1999), Development of a high-quantum-efficiency single-photon counting system.
• J. Kim, S. Takeuchi, Y. Yamamoto, and H. H. Hogue, Appl. Phys. Lett. 74, 902 (1999), Multiphoton detection using visible light photon counter.
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Faint laser pulses with Poissonian Distribution
II. 6. More Experiments with nonclassical …
2),0(),1(
!),(
0 kknPknP
enkknP
k
kn
→
−
≈>>
=
Poissonian distribution of expectation value k=0.1, n>0.
1 2
1 2
Poissonian distribution of expectation value k=0.01, n>0.
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Single photons on demand from a single molecule
II. 6. More Experiments with nonclassical …
B. Lounis and W. E. Moerner, Nature 407, 491 (2000)
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Single photons on demand from a single molecule
II. 6. More Experiments with nonclassical …
B. Lounis and W. E. Moerner, Nature 407, 491 (2000)
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Indistinguishable photons from a single-photon source
II. 6. More Experiments with nonclassical …
(ns)
3 ps100 ps - 300 ps
10 ps
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Indistinguishable photons from a single-photon source
II. 6. More Experiments with nonclassical …
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Coherent single-photon generation in ion-trap cavity-QED
II. 6. More Experiments with nonclassical …
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Coherent single-photon generation in ion-trap cavity-QED
II. 6. More Experiments with nonclassical …
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High-quantum-efficiency single photon counting system
Visible light photon counter (VLPC) with cryostat system
II. 6. More Experiments with nonclassical …
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II. 6. More Experiments with nonclassical …
High-quantum-efficiency single photon counting system
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High-quantum-efficiency single photon counting system
II. 6. More Experiments with nonclassical …
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Multiphoton detection using visible light photon counter
II. 6. More Experiments with nonclassical …
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III. Beams of Light 7. Squeezing from 2nd and 3rd Order Nonlinearities
TopicsSqueezing in time domain Quadratures of the electro-magnetic field Phasor diagramFormal description of coherent and squeezed statesThe beam splitter and vacuum fluctuationsχ(2)-squeezing and χ(3)-Kerr-squeezing
Literature• D. F. Walls and G. J. Milburn, Quantum Optics, Springer-Verlag, Berlin 1995.• G. Breitenbach and S. Schiller, J. Mod. Opt. 44, 2207 (1997),
Homodyne tomography of classical and non-classical light.• R. E. Slusher et al., Phys. Rev. Lett. 55, 2409 (1985) Observation of squeezed
states generated by four-wave mixing in an optical cavity.
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III. 7. Squeezing from 2nd and 3rd order ...
The electric field operator at a fixed position for a certain polarization may be written in the following form:
ˆ E (t) = E0,k(ωk) ˆ a ke−iωk t + ˆ a k
†eiωkt[ ]k
∑
ˆ a =ˆ X 1 + i ˆ X 2
2
ˆ a † =ˆ X 1 − i ˆ X 2
2
ˆ a , ˆ a †[ ]=1
With the operators of the dimensionless electric field amplitude:
ℜ( ˆ a ) ≡ ˆ X 1 /2 ˆ X 1 = ˆ X 1† = ˆ a + ˆ a †
ℑ( ˆ a ) ≡ ˆ X 2 /2 ˆ X 2 = ˆ X 2† = −i( ˆ a − ˆ a †)
ˆ X 1, ˆ X 2[ ]= 2i ⇒ ∆ ˆ X 1∆ ˆ X 2 ≥1
⇒
Quantization of the Electromagnetic Field
annihilation op.:
creation op.:
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III. 7. Squeezing from 2nd and 3rd order ...
The electric field vector at a fixed position for a certain polarization may be written in the following form:
ˆ E (t) = E0,k(ωk) ˆ a ke−iωk t + ˆ a k
†eiωkt[ ]k
∑
Quantization of the Electromagnetic Field
⇒ ˆ E (t) = E0,k(ωk) ˆ X 1,k cos(ωkt) + ˆ X 2,k sin(ωkt)[ ]k
∑
QuadraturesQuadrature amplitudes,(Amplitude quadrature amplitude,Phase quadrature amplitude)
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lα
mαml+α
φ
Phasor Diagram for a Classical FieldIII. 7. Squeezing from 2nd and 3rd order ...
X2/2
X1/2ℜ(α)
ℑ(α)
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ℜ(α)
Phasor Diagram for a Classical FieldIII. 7. Squeezing from 2nd and 3rd order ...
lα
mαml+α
Constructive Interference:
X2/2
X1/2
ℑ(α)
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Phasor Diagram for a Classical FieldIII. 7. Squeezing from 2nd and 3rd order ...
lα
mα
Destructive Interference:
ℜ(α)
ℑ(α)
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Coherent state
)ˆ(aℜ
)ˆ(aℑ
α
III. 7. Squeezing from 2nd and 3rd order ...
α = ˆ a = α ˆ a α
∆ ˆ X 1 = ∆ ˆ X 2 =1
∆ ˆ X 1
(Complex amplitude)
(Minimum uncertainty)
Phasor of the quantized field with Gaussian noise distribution(“ball on the stick”)
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Coherent state
)ˆ(aℜ
)ˆ(aℑ
α
E
t
III. 7. Squeezing from 2nd and 3rd order ...
α = ˆ a = α ˆ a α
∆ ˆ X 1 = ∆ ˆ X 2 =1
∆ ˆ X 1
(Complex amplitude)
(Minimum uncertainty)
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Phase squeezed state
III. 7. Squeezing from 2nd and 3rd order ...
t
)ˆ(aℜ
)ˆ(aℑ
α
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Amplitude squeezed state
III. 7. Squeezing from 2nd and 3rd order ...
t
)ˆ(aℜ
)ˆ(aℑ
α
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III. 7. Squeezing from 2nd and 3rd order ...
Measured quantum noise; a) coherent vacuum, c) amplitude squeezingb) squeezed vacuum d) phase squeezing
[G. Breitenbach and S. Schiller, J. Mod. Opt. 44, 2207 (1997)]
Time [ms] Time [ms]N
oise
cur
rent
[a.u
.]N
oise
cur
rent
[a.u
.]
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III. 7. Squeezing from 2nd and 3rd order ...
State Representations of the Quantized Field
ˆ H = hωkk
∑ ˆ a k† ˆ a k +
12
⎛ ⎝ ⎜
⎞ ⎠ ⎟
ˆ a † ˆ a n = ˆ n n = n n
ˆ a n = n n −1
ˆ a † n = n +1 n +1 n =ˆ a †( )n
n!0
Fock States (Number States)
Hamiltonian of the electromagnetic field
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III. 7. Squeezing from 2nd and 3rd order ...
Coherent States
ˆ a α =α α
ˆ a † α =α* α
ˆ n = α ˆ n α =α*α = α 2
α = e− α 2 / 2 αn
n!∑ n ⇒ P(n) = n α
2=
α2n
n!e− α 2
α = ˆ D (α) 0 = exp(αˆ a † −α* ˆ a ) 0
Eigenvalue equation (complex)
Displacement operator
Poissonian distribution
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III. 7. Squeezing from 2nd and 3rd order ...
Squeezed States
α,ε = ˆ D (α) ˆ S (ε) 0 ε = rSe2iθ S
ˆ S = exp 12
ε* ˆ a 2 −12
εˆ a †2⎛ ⎝ ⎜
⎞ ⎠ ⎟
ˆ n = α,ε ˆ n α,ε = α 2 + sinh2(rS ) ≥ α 2
ˆ S †(ε) ˆ Y 1 + i ˆ Y 2( )ˆ S (ε) = ˆ Y 1e−rS + i ˆ Y 2e
rS
⇒ ∆ ˆ Y 1 = e−rS , ∆ ˆ Y 2 = erS , ˆ Y 1 + i ˆ Y 2 = ˆ X 1 + i ˆ X 2( )e−iθ S
Degree and angle of squeezing
Squeezing operator
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Optical Parametric Amplification
ˆ X 1
ˆ X 2
Generation of amplitude squeezed light
ϕϕ=90°=90°
ˆ X 1(t) = eχt ˆ X 1(0)ˆ X 2(t) = e−χt ˆ X 2(0)
χ < 0
III. 8. Generation and Detection of Squeezed Light (A)
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Optical Parametric Amplification
ϕϕ=0°=0°
Generation of phase squeezed light
Generation of amplitude squeezed light
III. 8. Generation and Detection of Squeezed Light (A)
ˆ X 1(t) = eχt ˆ X 1(0)ˆ X 2(t) = e−χt ˆ X 2(0)
χ > 0
ˆ X 1
ˆ X 2
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Kerr squeezingIII. 7. Squeezing from 2nd and 3rd order ...
Kerr effect:Intensity dependent phase shift
X1
X2
α2 >> 1
ϕ << 1
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III. Beams of Light 8. OPO/OPA Squeezing Experiments in the
CW Laser Regime (A)TopicsSqueezing in frequency domain Phasor diagram and modulation sidebandsQuadratures in the 2-Photon-FormalismOptical parametric oscillation and amplification (OPO,OPA)Squeezed light from a degenerate OPO / OPAEquation of motion for the nonlinear cavity
Literature• D. F. Walls and G. J. Milburn, Quantum Optics, Springer-Verlag, Berlin 1995.• C. M. Caves, Phys. Rev. Lett. 31, 3068 (1985),
New Formalism for two-photon quantum optics.• M. J. Collett and C. W. Gardiner, Phys. Rev. A 30, 1386 (1984)
Squeezing of intracavity and traveling-wave light fields produced in parametric amplification.
• K. Schneider, M. Lang, J. Mlynek, and S. Schiller, Opt. Exp. 2, 59 (1998), Generation of strongly squeezed light at 1064 nm.
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Phasors in frequency space (amplitude squeezing)
III. 8. OPA/OPO Squeezing Experiments… (A)
Ω
X1
E0
ω+Ω0
ω−Ω0
X2
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Quadrature Noise OperatorsNoise operator diagrams for a coherent and phase squeezed beam
( )Ω1Xδ
( )Ω2Xδ
1-1
-1
1
δ ˆ X 1 Ω( )= δˆ a Ω( )+ δˆ a † −Ω( )δ ˆ X 2 Ω( )= −i δˆ a Ω( )−δˆ a † −Ω( )( )
ˆ a Ω( )= α + δˆ a Ω( )δˆ a Ω'( ),δˆ a † Ω( )[ ]= δ Ω− Ω'( )
Linearized annihilation and creation operators
III. 8. OPA/OPO Squeezing Experiments… (A)
ˆ X 1(Ω) = ˆ X 1†(Ω) = ˆ a (Ω) + ˆ a †(−Ω)
ˆ X 2(Ω) = ˆ X 2†(Ω) = −i( ˆ a (Ω) − ˆ a †(−Ω))
ˆ X 1(Ω), ˆ X 2(Ω)[ ]= 2i
⇒ ∆ ˆ X 1(Ω)∆ ˆ X 2(Ω) ≥1Heisenberg Uncertainty Relation
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Squeezed Light from an OPASqueezed beam
Squeezed beam
Coherent Coherent beambeam
III. 8. OPA/OPO Squeezing Experiments… (A)
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A. Franzen
III. 8. OPA/OPO Squeezing Experiments… (A)
OPA layout
MgO LiNO – hemilithic crystal7.5mm x 5mm x 2.5 mm
Radius of curvature: 10 mm HR=99.97% at 1064 nm
Flat surfaceAR at 1064 nm and 532 nm
Losses0.1 %/cm at 1064 nm4 %/cm at 532 nm
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A. Franzen
III. 8. OPA/OPO Squeezing Experiments… (A)
OPA layout
MgO LiNO – hemilithic crystal7.5mm x 5mm x 2.5 mm
Radius of curvature: 10 mm HR=99.97% at 1064 nm
Flat surfaceAR at 1064 nm and 532 nm
Losses0.1 %/cm at 1064 nm4 %/cm at 532 nm
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OPA layout
MgO LiNO – hemilithic crystal7.5mm x 5mm x 2.5 mm
Radius of curvature: 10 mm HR=99.97% at 1064 nm
Flat surfaceAR at 1064 nm and 532 nm
Output coupler: R=94% at 1064 nm
Finesse ~ 100Waist ~ 32 µmFSR ~ 9 GHzγ = 90 MHz
A. Franzen
III. 8. OPA/OPO Squeezing Experiments… (A)
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III. 8. OPA/OPO Squeezing Experiments… (A)
H. Vahlbruch
68
III. 8. OPA/OPO Squeezing Experiments… (A)
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Equation of Motion for OPA/OPO (SHG) CavityIII. 8. OPA/OPO Squeezing Experiments… (A)
22211221
221121
ˆ2ˆ2ˆ2ˆ2
ˆ)(ˆ
ˆ2ˆ2ˆ2ˆˆˆ)(ˆ
inlossb
incouplb
incouplbresres
lossb
couplb
couplbres
invac
lossa
incoupla
incouplaresresres
lossa
coupla
couplares
BBBabb
AAAbaaa
δγγγεγγγ
δγγγεγγγ
++++++−=
+++++++−= +
&
&
Equations of motion
)2(χ1ˆ in
frontA
2ˆ inbackA
2ˆ outbackA
1ˆ outfrontA
ˆ a res+ , ˆ a res
ˆ b res+ , ˆ b res
lossγ
1couplγ2couplγ
invacAout
lossA
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III. 8. OPA/OPO Squeezing Experiments… (A)
OPA Squeezing
H. Rehbein
Front seeded via R=94%
Back seeded via R=99.97%
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III. 8. OPA/OPO Squeezing Experiments… (A)
OPA Squeezing
H. Rehbein
Front seeded via R=94%
Back seeded via R=99.97%
Front seeded via R=94%
Back seeded via R=99.97%
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III. Beams of Light 9. OPO/OPA Squeezing Experiments in the
CW Laser Regime (B)
TopicsSqueezed light from a degenerate OPO / OPA (revisited)Homodyne detectionQuantum state tomographyFrequency dependent squeezing
Literature• L.-An Wu, M. Xiao, and H. J. Kimble, J. Opt. Soc. Am. B 4, 1465 (1987),
Squeezed states of light from an optical parametric oscillator.• G. Breitenbach and S. Schiller, J. Mod. Opt. 44, 2207 (1997),
Homodyne tomography of classical and non-classical light.• S. Chelkowski, H. Vahlbruch, B. Hage, A. Franzen, N. Lastzka, K. Danzmann, and
R. Schnabel, Phys. Rev A (2005), accepted,Experimental characterization of frequency-dependent squeezed light.
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III. 9. OPA/OPO Squeezing Experiments… (B)
Electric Polarization
Taylor expansion of electric polarization of media in electric and magnetic fields:
( )...)3()2()3()2(0 +++++= jlkijkljkijklkjijklkjijkjiji EBBhEBhEEEEEEP χχχε
SHG,OPA THG, Kerr effect Faraday effect Cotton-Mouton effect
zyxlkji ,,,,, =
Considering second order terms more explicitly:
( ) ( ) ( ) ( )∑ −=−jk
kkjjkjiijkii EEP ωωωωωχεω ,,)2(0
)2(
0=++− kji ωωω
74
Optical Parametric Amplification
ϕϕ=0°=0°
III. 9. OPA/OPO Squeezing Experiments… (B)
ˆ X 1(t) = eχt ˆ X 1(0)ˆ X 2(t) = e−χt ˆ X 2(0)
χ > 0
ˆ X 1
ˆ X 2
75
(Squeezed) signal beam
Intense local oscillator
Phase shift θ
Electrical current
V(ˆ i −) ≅ αLO2 ⋅ δ ˆ X 1
2 cos2 θ + δ ˆ X 22 sin2 θ( )= αLO
2 ⋅ δ ˆ X 2 θ( )
The Balanced Homodyne Detection
Interfering
50/50 beam splitter
III. 9. OPA/OPO Squeezing Experiments… (B)
76
ˆ a 1ˆ a 2
⎛
⎝ ⎜
⎞
⎠ ⎟ =
12
1 11 −1
⎛
⎝ ⎜
⎞
⎠ ⎟
ˆ a Aeiθ
ˆ a B
⎛
⎝ ⎜
⎞
⎠ ⎟
ˆ n 1 = ˆ a 1† ˆ a 1 =
12
ˆ a A† e−iθ + ˆ a B
†( ) ˆ a Aeiθ + ˆ a B( ), ˆ n 2 = ˆ a 2† ˆ a 2 =
12
ˆ a A† e−iθ − ˆ a B
†( ) ˆ a Aeiθ − ˆ a B( )ˆ n − = ˆ n 1 − ˆ n 2 = ˆ a A
† ˆ a Be−iθ + ˆ a B† ˆ a Aeiθ
ˆ a =α + δˆ a , α =α*, δˆ a = 0, αA2 >>αB
2 , δˆ a 2 , ˆ X (θ) = ˆ a e−iθ + ˆ a †eiθ
∆2 ˆ n − ≡ ˆ n −2 − ˆ n −
2 ≈ αA2 ∆2 ˆ X B (θ)
The Balanced Homodyne DetectionIII. 9. OPA/OPO Squeezing Experiments… (B)
ˆ a A
ˆ a B
ˆ a 1
ˆ a 2
θ
77
OPA, Noise Power of Coherent and Squeezed Light
δ ˆ X 12
δ ˆ X 22
δ ˆ X coh2
θ=0 θ=π/2
11.2 dB
3.1 dB
III. 9. OPA/OPO Squeezing Experiments… (B)
78
OPA, Noise Power of Coherent and Squeezed Light
III. 9. OPA/OPO Squeezing Experiments… (B)
79
Tomography / Noise Histogram
III. 9. OPA/OPO Squeezing Experiments… (B)
80
Tomography / Wigner-Function Plots
III. 9. OPA/OPO Squeezing Experiments… (B)
81
Frequency Dependent Squeezing
III. 9. OPA/OPO Squeezing Experiments… (B)
82
Frequency Dependent Squeezing
III. 9. OPA/OPO Squeezing Experiments… (B)
83
III. Beams of Light10. Polarization and Spatial Mode Squeezing
TopicsQuantum noise in a polarimeterStokes operators and Quantum Poincaré SphereGeneration of polarization squeezed lightQuantum noise in a pointing measurementThe TEM00 flipped modeGeneration of spatial mode squeezed light
Literature• B. A. Robson, The Theory of Polarization Phenomena (Clarendon, Oxford, 1974)• R. Schnabel, W. P. Bowen, N. Treps, H.-A. Bachor, T. C. Ralph, and P. K. Lam,
Stokes-operator-squeezed continuous-variable polarization states,Phys. Rev. A 67, 012316 (2003), Phys. Rev. Lett. 88, 093601 (2002).
• N. Treps, U. Andersen, B. Buchler, P.K. Lam, A. Maitre, H.-A. Bachor, and C. Fabre, Surpassing the Standard Quantum Limit for Optical Imaging Using Nonclasical Multimode Light, Phys. Rev. Lett. 88, 203601 (2002), Science 301, 940 (2003).
84
Spectrum analyser
Coherent state, H
Polarization rotatingsample
λ/245°
III. 10. Polarization and Spatial Mode Squeezing
Quantum Noise in a Polarimeter
Vacuum, H,V
Vacuum, H,V
By injecting an (amplitude, θ=0) squeezed vacuum at the first beamsplitter the quantum noise in the above measurement is reduced.What observable is squeezed then?
θ
85
Continuous Variable Polarization StatesMeasurement of Stokes Parameters
III. 10. Polarization and Spatial Mode Squeezing
86
III. 10. Polarization and Spatial Mode Squeezing
Stokes Parameters in Classical Optics
= α H2
+ αV2,
= α H2
− αV2,
= α HαV eiθ + αVα H e− iθ ,
= −iα HαV eiθ + iαVα H e− iθ .
S0 = αH
2+ αV
2
S1 = αH
2− αV
2
S2 = α+45º
2− α−45º
2
S3 = αRCirc
2− αLCirc
2
Decomposition into two orthogonal fields in H/V-basiswith real amplitudes α of relative phase θ:
87
III. 10. Polarization and Spatial Mode Squeezing
Stokes Parameters / Poincaré Sphere
Radius ofClassical Poincaré sphere:
For completelypolarized light:
Degree of polarization:
[G.G.Stokes, Trans.Camb.Phil., 9, 399 (1852)]0 ≤
S12 + S2
2 + S32
S0
≤1
Total light intensity:
S12 + S2
2 + S32 = S0
S12 + S2
2 + S32
S0
88
Stokes Operators in Quantum OpticsIII. 10. Polarization Squeezed Light
ˆ S 0 = ˆ a H ˆ a H + ˆ a V
ˆ a V , ˆ S 2 = ˆ a H ˆ a V eiθ + ˆ a V
ˆ a He−iθ
ˆ S 1 = ˆ a H ˆ a H − ˆ a V
ˆ a V , ˆ S 3 = −iˆ a H ˆ a V eiθ + iˆ a V
ˆ a He− iθ ,
ˆ a k, ˆ a l†[ ]= δkl , k, l ∈ H,V , σ A
2σ B2 ≥
12i
ˆ A , ˆ B [ ]⎛ ⎝ ⎜
⎞ ⎠ ⎟
2
ˆ S 1, ˆ S 2[ ]= 2i ˆ S 3 , ˆ S 2, ˆ S 3[ ]= 2i ˆ S 1 , ˆ S 3, ˆ S 1[ ]= 2i ˆ S 2 .
V1V2 ≥ ˆ S 32, V2V3 ≥ ˆ S 1
2, V3V1 ≥ ˆ S 2
2.
Commutation relations of Stokes operators
Uncertainty relations of Stokes operators
III. 10. Polarization and Spatial Mode Squeezing
89
III. 10. Polarization and Spatial Mode Squeezing
Stokes Operator VariancesIII. 10. Polarization Squeezed Light
ˆ a H ,V = α H ,V +12
δ ˆ X H ,V+ + iδ ˆ X H ,V
−( )
V0 = V1
V1 = αH2 δ ˆ X H
+( )2+ αV
2 δ ˆ X V+( )2
V2 θ = 0( )= αV2 δ ˆ X H
+( )2+ αH
2 δ ˆ X V+( )2
V3 θ = 0( )= αV2 δ ˆ X H
−( )2+ αH
2 δ ˆ X V−( )2
For a coherent beam:
= αH2 + αV
2 = ˆ n ,
= αH2 + αV
2 = ˆ n ,
= αH2 + αV
2 = ˆ n ,
= αH2 + αV
2 = ˆ n .
90
III. 10. Polarization and Spatial Mode Squeezing
Quantum Poincaré Sphere
91
III. 10. Polarization and Spatial Mode Squeezing
Phase difference locked to θ=0.
92
Results from a Coherent Polarization StateIII. 10. Polarization and Spatial Mode Squeezing
93
III. 10. Polarization and Spatial Mode Squeezing
Polarization Squeezing from two Amplitude Squeezed Beams
94
III. 10. Polarization and Spatial Mode Squeezing
Polarization Squeezing from two Phase Squeezed Beams
III. 10. Polarization Squeezed Light
95
III. 10. Polarization and Spatial Mode Squeezing
Uncertainty Volumes of Polarization States
‘Cigar’ State ‘Pancake’ State
III. 10. Polarization Squeezed Light
(Measured at 8.5 MHz)
96
III. 10. Polarization and Spatial Mode Squeezing
Polarization Squeezing from two Quadrature Squeezed Beams
III. 10. Polarization Squeezed Light
97
III. 10. Polarization and Spatial Mode Squeezing
“Quantum Laser Pointer”
What is the relevant spatial mode that provides the measurement quantum noise?
Spectrum analyser
Coherent state
Laser Pointing
Vacuum, spatial mode
θ
?
III. 10. Polarization and Spatial Mode Squeezing
98
III. 10. Polarization and Spatial Mode Squeezing
“Quantum Laser Pointer”
Spectrum analyser
Coherent state
Laser Pointing
Vacuum, spatial mode
θ
?
III. 10. Polarization and Spatial Mode Squeezing
99
III. 10. Polarization and Spatial Mode Squeezing
1-Dimensional Spatial Mode Squeezing
N. Treps et al. (2002)
III. 10. Polarization and Spatial Mode Squeezing
100
III. 10. Polarization and Spatial Mode Squeezing
2-Dimensional Spatial Mode Squeezing
N. Treps et al. (2003)
III. 10. Polarization and Spatial Mode Squeezing
101
III. 10. Polarization and Spatial Mode Squeezing
2-Dimensional Spatial Mode Squeezing
N. Treps et al. (2003)
π 0
0 π
III. 10. Polarization and Spatial Mode Squeezing
102
III. 10. Polarization and Spatial Mode Squeezing
2-Dimensional Spatial Mode Squeezing
N. Treps et al. (2003)
III. 10. Polarization and Spatial Mode Squeezing
103
Coherent State
Coherent State
Coherent State
Laser Beam Input Electrical Noise Power Output
Shot Noise
Shot Noise
Shot Noise-
-
Polarization Squeezed
State
Spatially Squeezed State
Amplitude Squeezed State
Shot NoiseBelow
Shot NoiseBelow
Shot NoiseBelow
[R.E.Slusher et al.,1985]
[N.Treps et al.,2002]
[W.Bowen et al.,2002]
Squeezed States - SummaryIII. 10. Polarization and Spatial Mode SqueezingIII. 10. Polarization and Spatial Mode Squeezing
104
III. Beams of Light11. Entangled Laser Beams
TopicsWhat are the characteristics of an experiment with entangled laser
beams?Entanglement of continuous variablesFirst realization of the EPR Paradox for continuous variablesThe EPR criterion for entanglementThe inseparability criterion for entanglement
Literature• M. D. Reid, Phys. Rev. A 40, 913 (1989),
Demonstration of the EPR-Paradox using nondegenerate parametric amplification.• Z. Y. Ou, S. F. Pereira, H. J. Kimble, and K. C. Peng, Phys. Rev. Lett. 68, 3663
(1992), Realization of the EPR Paradox for continuous variables.• W. P. Bowen, R. Schnabel, P. K. Lam, and T. C. Ralph, Phys. Rev. Lett. 90, 043601
(2003), Phys. Rev. A 69 (2004),Experimental Investigation of Criteria for continuous variable entanglement.
105
Experimental SetupIII. 11. Entangled Laser Beams
106
Amplitude squeezed state
Phase squeezed state
EPR-entangled pair of laser beams [Einstein, Podolski, Rosen 1935]
Measurement of Amplitude
Measurement of Phase
50/50Beamsplitter
Entanglement
Inferred Quadratures
III. 11. Entangled Laser Beams
‐
+
107
Entanglement Criteria for Continuous Var.III. 11. Entangled Laser Beams
108
CV Entanglement CriteriaIII. 11. Entangled Laser Beams
Conditional variance criterion
Inseparability criterion
[M.D.Reid and P.D.Drummond, Phys.Rev.Lett. 60, 2731 (1988)]
[L-M. Duan, G.Giedke, J.I.Cirac and P.Zoller, Phys.Rev.Lett. 84, 2722 (2000)]
Ε = ming + /− δ ˆ X x
+ − g+δ ˆ X y+( )2
δ ˆ X x− − g−δ ˆ X y
−( )2⎧ ⎨ ⎩
⎫ ⎬ ⎭
≡ ∆2 ˆ X x|y+ ⋅ ∆2 ˆ X x|y
− <1
Ι = δ ˆ X x+ +δ ˆ X y
+( )2δ ˆ X x
− −δ ˆ X y−( )2
≡ ∆2 ˆ X x+y+ ⋅ ∆2 ˆ X x−y
− <1
(g=1, +/- chosen to provide minima)
109
Entangled Quadrature Noise VariancesIII. 11. Entangled Laser Beams
Degree of Inseparability ΙAverage of quadrature noise variances of individual entangled beams
110
Entanglement Criteria for Continuous Var.III. 11. Entangled Laser Beams
Bowen et al. (2003)
Ι=0.44
Ε=0.58
111
III. Beams of Light12. Kerr Squeezing Experiments in the Pulsed
Laser Regime
TopicsOptical Solitons in FibersKerr squeezingEntangled laser pulsesQuadrature noise measurements on laser pulses
Literature• S. Schmitt, J. Ficker, M. Wolff, F. König, A. Sizmann, and G. Leuchs,
Phys. Rev. Lett. 81, 2446-2449 (1998), Photon-number squeezed solitons from an asymmetrical fiber optic Sagnacinterferometer.
• Ch. Silberhorn, P. K. Lam, O. Weiß, F. König, N. Korolkova, and G. Leuchs,Phys. Rev. Lett. 86, 4267-4270 (2001),Generation of continuous variable Einstein-Podolsky-Rosen entanglement via the Kerr nonlinearity in an optical fibre.
112
III. 12. Kerr Squeezing Experiments
Electric Polarization
Taylor expansion of electric polarization of media in electric and magnetic fields:
Pi =ε0 χij(1)E j + χijk
(2)E j Ek + χijkl(3)E j EkEl + hijk
(2)BkE j + hijkl(3)BkBl E j + ...( )
SHG,OPA THG, Kerr effect Faraday effect Cotton-Mouton effect
zyxlkji ,,,,, =
Considering third order terms more explicitly:
Pi(3) −ωi( )=ε0d χijkl
(3) −ωi,ω j,ωk,ωl( )E j ω j( )Ek ωk( )jkl∑ El ωl( )
−ωi +ω j +ωk +ωl = 0d=degeneracy
113
Kerr squeezingIII. 7. Squeezing from 2nd and 3rd order ...
Kerr effect:Intensity dependent phase shift;quadrature squeezing is produced for small angles
X1
X2
α2 >> 1
ϕ << 1
114
III. 12. Kerr Squeezing Experiments
Squeezed Laser Pulses
115
III. 12. Kerr Squeezing Experiments
Squeezed Laser Pulses
116
III. 12. Kerr Squeezing Experiments
Entangled Laser Pulses
( )%0.1%5.51 ±(96% visibility)
117
III. 12. Kerr Squeezing Experiments
Entangled Laser Pulses
Shot-noise
Shot-noise
p-pol
SQZ4dB
s-pol
SQZ4dB
118
CV Entanglement CriteriaIII. 11. Entangled Laser Beams
Conditional variance criterion
Inseparability criterion
[M.D.Reid and P.D.Drummond, Phys.Rev.Lett. 60, 2731 (1988)]
[L-M. Duan, G.Giedke, J.I.Cirac and P.Zoller, Phys.Rev.Lett. 84, 2722 (2000)]
Ε = ming + /− δ ˆ X x
+ − g+δ ˆ X y+( )2
δ ˆ X x− − g−δ ˆ X y
−( )2⎧ ⎨ ⎩
⎫ ⎬ ⎭
≡ ∆2 ˆ X x|y+ ⋅ ∆2 ˆ X x|y
− <1
Ι = δ ˆ X x+ +δ ˆ X y
+( )2δ ˆ X x
− −δ ˆ X y−( )2
≡ ∆2 ˆ X x+y+ ⋅ ∆2 ˆ X x−y
− <1
(g=1, +/- chosen to provide minima)
119
III. 12. Kerr Squeezing Experiments
Kerr Squeezing in CW Nonlinear Cavity
21 ˆ2ˆ2ˆˆˆˆ)(ˆ inlossincouplresresresres
losscouplres AAaaaiaa γγµγγ ++++−= +&
)3(χ1ˆ inA
2ˆ invacuumA
2ˆ outlossA
1ˆ outA
resres aa ˆ,ˆ+ lossγcouplγ
Equation of motion
120
IV. Applications of Nonclassical Light 13. QND, Teleportation and Entanglement Swapping
TopicsExperiments with single photons and laser beamsCharacterization of Quantum Non-demolition (QND) measurements:
- Signal transfer and conditional varianceCharacterization of quantum teleportation and entanglement swapping:
- Fidelity- Signal transfer and conditional variance
Literature• P. Grangier. J.A. Levenson, and J.-P. Poizat, Nature 396, 537 (1998),
Quantum non-demolition measurements in optics.• V.B. Braginski and F.Y. Khalili, Rev. Mod. Phys. 68, 1 (1996),
Quantum non-demolition measurements – the route from toys to tools.• D. Bouwmeester et al., Nature 390, 575 (1997),
Experimental quantum teleportation.• W. P. Bowen et al., Phys. Rev. A 67, 032302 (2003),
Experimental investigation of continuous-variable quantum teleportation.
121
Quantum Non-demolition MeasurementsIV. 13. QND, Teleportation ...
T = Tm + Ts =ℜm
out
ℜsin +
ℜsout
ℜsin 0 < T < 2
Signal-Transfer:
Vs|m = Vsout −
δXsoutδXm
out 2
Vmout 0 < V < ∞
Conditional Variance:
T>1 and 0< V < 1QND:
122
Quantum Non-demolition MeasurementsIV. 13. QND, Teleportation ...
Noise-less Amplification
Quantum State Preparation
123
Quantum TeleportationIV. 13. QND, Teleportation ...
• Can quantum information be copied perfectly? No! (No-Cloning-Theorem)
• Can we extract all the information from a system? No!
• Can we send all the information of a system fromone place to another (via classical channels)? Yes, we can!
[Bennett et al. 1993]
124
Quantum Teleportation - CharacterizationIV. 13. QND, Teleportation ...
inoutF ψψ=Fidelity:
,10 ≤≤ FArbitrary amount of copies
Finite amount of copies
No equally good copy can exist
Classical information transfer:
Quantum regime I:
Quantum regime II: ,13/2
,3/25.0
,5.00
≤<
≤<
≤≤
F
F
F
125
Quantum TeleportationIV. 13. QND, Teleportation ...
Bouwmeester et al. (1997)
126
Generation of maximally entangled statesIV. 13. QND, Teleportation ...
Ψ± =12
↔b ± b↔( )
φ ± =12
bb ± ↔↔( )*
127
Quantum Teleportation (Single Photons)III. 13. QND, Teleportation ...
Bouwmeester et al. (1997)
128
IV. 13. QND, Teleportation ...
Teleportation of a single photon state was demonstrated by similar results from measurements on 90° and circular polarized signal states
Bouwmeester et al. (1997)
Quantum Teleportation (Single Photons)
129
IV. 13. QND, Teleportation ...
Entanglement Swapping (Single Photons)
Entangling photons that never interacted
130
IV. 13. QND, Teleportation ...
Quantum Teleportation (Laser Beams)
131
IV. 13. QND, Teleportation ...
Quantum Teleportation (Laser Beams)
k± =α in
± 2⋅ 1− g±( )2
Vin± + Vout
± ,
ˆ X in±
Ω( )= 2α in
±
Ω( )+ δ ˆ X in±
Ω( ) ,
g± = αout± /α in
± .
Vin± = δ ˆ X in
± Ω( )2 ,Variance:
Electronic Gain:
F = e−(k+ +k− )⋅4 ⋅Vin
+Vin−
Vin+ + Vout
+( )⋅ Vin− + Vout
−( )⇒ Fidelity:
Sideband Modulation:
132
SqueezingIII. 11. Entangled Laser Beams
Coherent State Squeezed State
δ ˆ X + Ω( )2 δ ˆ X − Ω( )2 ≥1
δ ˆ X − Ω( )
δ ˆ X + Ω( )
δ ˆ X − Ω( )
δ ˆ X + Ω( )
Heisenberg Uncertainty Relation
133
Amplitude squeezed state
Phase squeezed state
EPR-entangled pair of laser beams [Einstein, Podolski, Rosen 1935]
Measurement of Amplitude
Measurement of Phase
50/50Beamsplitter
Entanglement
Inferred Quadratures
III. 11. Entangled Laser Beams
‐
+
134
IV. 13. QND, Teleportation ...
!?
Unknown quantum information
EPR I EPR II
Teleported quantum information
Measurement of phase
Measurement of amplitude
Displacement using g=1
?
50/50
Classical channels
Teleportation of Quadratures
135
IV. 13. QND, Teleportation ...
Unknown quantum information
“Teleported” classical information
Measurement of phase
Measurement of amplitude
Displacement using g=1
Classical channels
Vacuum Vacuum
!??
50/50
Teleportation of Quadratures
136
W.P. Bowen et al., Phys. Rev. A (2003)
Classical limitNo-cloning limit
Classical limit
No-cloning limit
Perfect teleportation
Teleportation of QuadraturesIV. 13. QND, Teleportation ...
137
Fidelity ResultsIV. 13. QND, Teleportation ...