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Danmarks Grundforskningsfond - Quantum Optics Center

QUANTOP. Danmarks Grundforskningsfond - Quantum Optics Center. Quantum teleportation between light and matter. Eugene Polzik. Niels Bohr Institute Copenhagen University. Quantum mechanical wonders (second wave). Quantum objects. cannot be measured. cannot be copied.

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Danmarks Grundforskningsfond - Quantum Optics Center

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  1. QUANTOP Danmarks Grundforskningsfond - Quantum Optics Center Quantum teleportation between light and matter Eugene Polzik Niels Bohr Institute Copenhagen University

  2. 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)

  3. Teleportation a la Star Trek, what’s 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

  4. Problem: electrons, atoms and humans cannot be described as a set of classical bits 00111010111000010101

  5. Bohr’s complementarity principle Perfect measurement of both position and momentum is impossible Minimal symmetric Uncertainty: 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.

  6. 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)

  7. Bell measurement Ensemble of 1012 atoms <n> = 0 – 500 photons Teleportation cartoon Classical communication entangled objects done!

  8. σ+ + σ- Singlet or e-bit – maximally entangled pair -1 0 + -1 1 Harvard, Caltech, GeorgiaTech Copenhagen, Caltech Ensembles of atoms Physics of entanglement Interaction↔entanglement=conservation of energy momentum angular momentum 0 -1 1 Single atom/ion Ann Arbor

  9. EPR paradox 1935 • 2 particles entangled in position/momentum • EPR state of light Caltech 1992 • EPR state of atoms Aarhus 2001 Einstein-Podolsky-Rosen (EPR) entanglement Canonical operators: position/momentum or real/imaginary parts of the e.-m. field amplitude, etc

  10. Einstein-Podolsky-Rosen entangled state Teleportation principle (canonical operators) L.Vaidman

  11. t Pulse: Canonical operators for light Coherent state:

  12. 450 -450 l/4 Canonical operators of light Y, Q can be efficiently measured Polarizing Beamsplitter 450/-450 Strong field A(t) x Quantum field a -> Y, Q Polarizing cube

  13. Quantum tomography – with many copies of a state Squeezed single photon state QUANTOP 2006 Wigner function Coherent state

  14. x Quantum state (Wigner function) y z Canonical quantum variables for an atomic ensemble: 4 3

  15. Orthogonally polarized Teleported operators – of quantum mode Strong field Extra benefit: homodyne measurements on quantum mode carried at beatnote frequency Ω Light modes and atomic levels 4 3

  16. Rotating frame spin Atomic operators Atoms: ground state Caesium Zeeman sublevels 4 3

  17. Decoherence from stray magnetic fields Magnetic Shields Special coating – 104 collisions without spin flips Object – gas of spin polarized atoms at room temperature Optical pumping with circular polarized light

  18. Quantum Noise of Atomic Spin –

  19. e.-m. vacuum 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),

  20. October 5, 2006 J.Sherson, H.Krauter, R.Olsson, B.Julsgaard, K.Hammerer, I.Cirac, and E.Polzik, Nature 443, 557 (2006).

  21. ?

  22. Teleportation of light onto a macroscopic atomic sample Pulse to be teleported <n>=0–200 photons Atoms – target object of teleportation

  23. Teleportation step 1: entanglement

  24. Upper sideband is teleported Light+Atoms: entangling Hamiltonian Off-resonant interaction entangles light and atoms D = 800 MHz 6P3/2 W = 0.3 MHz 6S1/2 + magnetic field

  25. 4 Atoms Entanglement via forward scattering of light

  26. Addition of amagnetic fieldcouples light to rotating spin states B 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]

  27. Teleportation step 2: Bell measurement

  28. 450 -450 l/4 Polarization homodyning - measure Y (or Q) Polarizing Beamsplitter 450/-450

  29. q y

  30. Teleportation step 3: classical communication

  31. 322 kHz RF field Magnetic shields

  32. pulse sequence Teleportation experiment feedback Teleported operators: pump 2ms 4ms verifying entangling+ Bell measurement

  33. Teleportation step 4: verification

  34. Mean values of operators are transferred Atomic variances are below a critical value verification XA=Jz PA=Jy

  35. Teleportation of coherent state n ≈ 500

  36. Teleported state readout determines atomic variance Input state readout Teleportation of a vacuum state of light

  37. Teleportation of a coherent state, n ≈ 5

  38. Raw data: atomic state for <n>=5 input photonic state Reconstructed teleported state, F=0.58±0.02

  39. Experimental quantum fidelity versus best classical case Upper bound on <n> ≈ 1000 – due to gain instability F quantum F classical = Anticipated qubit fidelity: Fqubit =72% (with feasible imperfections) Optimal gain

  40. 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

  41. 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, 1:06 PM ET LONDON (Reuters) Quantum information teleported from light to matter

  42. NBI - QUANTOP 2006

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