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Continuos-variable and EIT-based quantum memories: a common perspective Michael Fleischhauer Zoltan Kurucz Technische Universität Kaiserslautern DEICS.

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Presentation on theme: "Continuos-variable and EIT-based quantum memories: a common perspective Michael Fleischhauer Zoltan Kurucz Technische Universität Kaiserslautern DEICS."— Presentation transcript:

1 Continuos-variable and EIT-based quantum memories: a common perspective Michael Fleischhauer Zoltan Kurucz Technische Universität Kaiserslautern DEICS III / QUDAL Feb. 2006, Eilat, Israel

2 in collaboration with: Mikhail Lukin (Harvard) Eugene Polzik (Kopenhagen) Anders Sørensen (Kopenhagen) QUACS

3 quantum networks |>|> photons as information carrieratoms for storage and processing

4 atom-light interfaces: EIT scheme  (t) probe Fleischhauer, Lukin, PRL 2000; PRA 2002 Phillips et al. PRL 2001, Kuzmich et al. Nature 2005 Eisaman et al. Nature 2005 quasi-particle picture ? Faraday scheme  probe Julsgaard, Sherson, Cirac, Fiurášek, Polzik, Nature 2004 Sørenson, Mølmer, … quant-ph/0505170, … continuous variable picture

5 outline:outline: perfect single-mode quantum memory Faraday scheme off-resonant Raman scheme EIT scheme

6 outline:outline: perfect single-mode quantum memory Faraday scheme off-resonant Raman scheme EIT scheme

7 outline:outline: perfect single-mode quantum memory Faraday scheme off-resonant Raman scheme EIT scheme

8 outline:outline: perfect single-mode quantum memory Faraday scheme off-resonant Raman scheme EIT scheme

9 perfect single-mode memory: perfect single-mode memory: light modeatomic ensemble XP X P LL A A map of ideal q-memory: M symplectic 2 x 2 matrices i

10 bi-linear Hamiltonian: assume:

11 solution of Heisenberg equation: if determinant is nonzero (=1):

12 generic Hamiltonians for ideal mapping  (T) =  / 2

13 Faraday rotation: microscopic Hamiltonian Julsgaard, Sherson, Cirac, Fiurášek, Polzik, Nature 2004 Sørenson, Mølmer et al. quant-ph/0505170 strong coherent field with linear polarization in x direction i.e. x =  + and  - atoms are spin polarized in x direction, i.e. (|1> + |2>)/  2 z x y

14 Stokes parameters of polarization state of light Spins of atomic ensemble „macroscopic“ Hamiltonian constant of motion

15 x – pol. coherent input light initial atomic polarization „macroscopic“ Hamiltonian = |  | / 2 x 2 non-ideal Hamiltonian mapping

16 single-pass Faraday scheme: unitary evolution for time t requires atomic spin squeezing requires perfect detection & feedbeack L measurement of light component X  x and momentum displacement –x/t of atoms (feedback) Julsgaard et.al, Nature 2004

17 Gaussian state fidelity of single-pass scheme: non-Gaussian states (  = 0) coherent spin and light state, pefect detector (  =0),  F ≤ 82 % coh. spin state (CSS)

18 double-pass Faraday scheme: 1. unitary evolution with H for t requires either atomic spin squeezing but no feedback Sherson et al. quant-ph/0505170 1 2. unitary evolution with H for t´ 2 tt´= 1 or perfect detection & feedback but no squeezing

19 triple-pass Faraday scheme: ideal mapping w/o squeezing and feedback operator identity

20 EIT scheme:  Fleischhauer, Lukin, PRL 2000; PRA 2002; Phillips et al. PRL 2001, Kuzmich et al. Nature 2005; Eisaman et al. Nature 2005 dynamically controllable group velocity 2 3

21 „stopping“ of light:

22 Autler-Townes splitting   quasi-particle picture of EIT: large small

23 dark & bright-state polaritons: in adiabatic limit:

24 collective spin light-stopping = adiabatic rotation of DSP: E  spin

25 polariton excitations: |n  |S = -N/2  |0  |S = -N/2 + n   = 0  =  /2 polariton rotation: = ph at

26 time-dependent  : perfect mapping Hamiltonian effective Hamiltonian of dynamical EIT:

27 off-resonant Raman scheme: drive-field  + polarized atoms z- polarized g /  = g ´ /  ´  Faraday scheme S  22 zz

28 choose perfect mapping Hamiltonian drive-field  + polarized atoms z- polarized

29 summary:summary: perfect single-mode quantum memory single-pass Faraday scheme + squeezing and feedback double-pass Faraday scheme + squeezing or feedback triple-pass Farday scheme EIT scheme


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