A1258150714iAwnz

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Quantum teleportation between light and matter
Eugene Polzik
Niels Bohr Institute Copenhagen University
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Quantum mechanical wonders (second wave)
Quantum objects
cannot be measured
cannot be copied
exist in superposition and entangled states
Quantum Information Science

• Quantum memory

• Communications with
• absolute security

• Computing with unprecedented speed

• Teleportation of objects (or at least of their
  quantum states)

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Teleportation a la Star Trek, whats the problem?
Problem Matter cannot be reversibly converted
into light!
Question If matter if not teleported, then what
is being transmitted?
Answer information - is what should be
transmitted
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Problem electrons, atoms and humans cannot
be described as a set of classical
bits 00111010111000010101
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The more precisely the position is determined,
the less precisely the momentum is known in this
instant, and vice versa. --Heisenberg 1927
Blegdamsvej 17, Copenhagen
Noncommuting operators
Heisenberg in 1927.
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Challenge of Quantum Teleportation transfer
two non-commuting operators from one system onto
another (Heisenberg picture)
equivalent to Transfer an unknown quantum state
from one system onto another (Schördinger
picture)
Teleportation experiments so far Light onto
light Innsbruck(97), Rome(97), Caltech(98),
Geneva, Tokyo, Canberra Single ion onto single
ion Boulder (04), Innsbruck (04)
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Teleportation cartoon
Classical communication
entangled objects
done!
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Physics of entanglement
Interaction?entanglementconservation of
energy momentum angular momentum
0
-1
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Single atom/ion Ann Arbor
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Einstein-Podolsky-Rosen (EPR) entanglement
Canonical operators position/momentum
or real/imaginary parts of
the e.-m. field amplitude, etc
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Teleportation principle (canonical operators)
L.Vaidman
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Canonical operators for light
Coherent state
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Canonical operators of light Y, Q can be
efficiently measured
Polarizing Beamsplitter 450/-450
Strong field A(t)
x
Quantum field a -gt Y, Q
Polarizing cube
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Quantum tomography with many copies of a state
Coherent state
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Canonical quantum variables for an atomic
ensemble
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3
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Light modes and atomic levels
4
3
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Atoms ground state Caesium Zeeman sublevels
4
3
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Object gas of spin polarized atoms at room
temperature
Optical pumping with circular polarized light
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Quantum Noise of Atomic Spin

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Classical benchmark fidelity for teleportation
of coherent states
Atoms
Best classical fidelity 50
K. Hammerer, M.M. Wolf, E.S. Polzik, J.I. Cirac,
Phys. Rev. Lett. 94,150503 (2005),
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October 5, 2006
J.Sherson, H.Krauter, R.Olsson, B.Julsgaard,
K.Hammerer, I.Cirac, and E.Polzik, Nature 443,
557 (2006).
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Teleportation of light onto a macroscopic atomic
sample
Pulse to be teleported ltngt0200 photons
Atoms target object of teleportation
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Teleportation step 1 entanglement
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LightAtoms entangling Hamiltonian
Off-resonant interaction entangles light and
atoms
D 800 MHz
6P3/2
W 0.3 MHz
6S1/2
magnetic field
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Entanglement via forward scattering of light
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Addition of a magnetic field couples light to
rotating spin states
y
z
Atomic Quantum Noise
2,4
2,2
2,0
1,8
1,6
1,4
1,2
Atomic noise power arb. units
1,0
0,8
0,6
0,4
0,2
0,0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
Atomic density arb. units
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Teleportation step 2 Bell measurement
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Polarization homodyning - measure Y (or Q)
Polarizing Beamsplitter 450/-450
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q
y
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Teleportation step 3 classical communication
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322 kHz RF field
Magnetic shields
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pulse sequence
Teleportation experiment
feedback
Teleported operators
pump
4ms
2ms
verifying
entangling
Bell measurement
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Teleportation step 4 verification
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verification
XAJz
PAJy
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Teleportation of coherent state n 500
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Teleportation of a vacuum state of light
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Teleportation of a coherent state, n 5
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Raw data atomic state for ltngt5 input
photonic state
Reconstructed teleported state, F0.580.02
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Experimental quantum fidelity versus best
classical case
Upper bound on ltngt 1000 due to gain
instability
F quantum
F classical
Anticipated qubit fidelity Fqubit 72
(with feasible imperfections)
Optimal gain
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Summary

• Teleportation between two mesoscopic objects of
  different nature
• a photonic pulse and an atomic ensemble
  demonstrated
• Distance 0.5 meter, can be increased (limited
  mainly
• by propagation losses)
• Extention to qubit teleportation possible
• Fidelity can approach 100 with more
  sophisticated measurement
• procedure plus using squeezed light as a probe

J. Sherson, H. Krauter, R. K. Olsson, B.
Julsgaard, K. Hammerer, I. Cirac, and ESP
quant-ph/0605095 , Nature, October 5, 2006
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Outlook June 2001
Scientists teleport two different objects POSTED
1113 GMT (1913 HKT), October 5, 2006
First Teleportation Between Light and Matter
J. Sherson, H. Krauter, R. K. Olsson, B.
Julsgaard, K. Hammerer, I. Cirac, and ESP
quant-ph/0605095 , Nature, October 5, 2006
Wed Oct 4, 106 PM ET LONDON (Reuters) Quantum
information teleported from light to matter
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NBI - QUANTOP 2006