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BEC research in Durham
Magnetic Field (G)157 159 161 163 165
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Cornish et al, PRL 85, 1795 (2000)
BEC with Tunable Interactions1. 85Rb BEC Experiment 2. Rb-Cs Mixtures
Thomas et al,J. Opt. B 5, S107 (2003)
Cs FeshbachResonance
133 Cs87 Rb
Staff: Simon Cornish, CSAStudents: Margaret Harris
Malcolm ParksPatrick Tierney
Finance: Royal SocietyEPSRC GR/S78339/01
Parker et al. PRL 90, 220401 (2003).Parker et al. PRL 92, 160403 (2004).
3. Theory: vortices,solitons, sound
Staff: Nick Proukakis, CSAStudents: Nick Parker
Eleni Sakallari (-07/04)Andrew Martin
Finance: EPSRC GR/S78339/01
~ 12 µm
Neutral atom quantum computing in optical lattices: far red or far blue?
C. S. Adams
University of Durham
MESUMA 04
Dresden 2004
University of Durham
OutlineUniversity of Durham
Good things for quantum computing
Scalability (optical lattices)
Low decoherence(large detuning)
Far-red Far-blue
3D CO2 single-site addressable
Switchable inteactions
State-selective single-atom transport
Collisional gates
Experiment
Magic Rydberg lattice
or
2. Neutral atoms in optical lattice.
Single-qubit addressable.- Patterned loading- Cavity QED- Microtraps
Switchable interactions.- Rydberg
Scaling to 2(3)D.
Low decoherence.
~ 12 µm
C. S. Adams et al. J. Phys. B. 36, 1933 (2003).
University of Durham
1. Ions. (ENS, Caltech, MPQ, Sussex)
Single-qubit addressable.
Switchable interactions.
Scaling to 2(3)D.
Low decoherence.
Architecture for a large-scale ion-trap quantum computer, D. Kielpinski, C. Monroe, D.J. Wineland Nature, 417, 709 (2002).
Quantum computing:atoms or ions?
3D CO2 lattice 10 x 10 x 10 sites
8.4 µm
Low decoherenceUniversity of Durham
Photon scattering rate for a trap frequency of 1 MHz
25 s-1 at 790 nm!
Nd:YAG
CO20.002s-1
Rb5p6p7p
5p
6p
5s
7p
Far redFar blue
λν 0
osc
U∝
λπη 02 a
∝Lamb-DickeBlue: less power
νx ~ 100 kHz
C. S. Adams et al. J. Phys. B. 36, 1933 (2003).
University of Durham Far infrared: 3D CO2 lattice
~ 12 µm
θ = atan(2)
θ
1. 11.8 µm lattice constant: single-atom addressable.2. Similar trap depths for most atoms (molecules).
P = 80 W
w0=50 µm
Saddle
νy ~ 75 kHz
Single-atom conveyor
8.4 µm
2
0
41
10−<U
ωh
Photon scattering rate
‘Blue’‘Red’
Single-atom tweezer
Diener et al. Phys. Rev. Lett. 36, 1933 (2003).
University of Durham
Wavelength
Range
Near-infra-red
Spin-dependent lattice
Single-atom cooling anddetection
Fluorescencedetection
Problems:
Optical pumping and heating
• Solid angle 1/100• Detect 100 photons (1 ms)• Heating 2 mK
0
1Raman sideband cooling
Repumper
C. Monroe, D.M. Meekhof, B.E. King, S.R. Jefferts, W.M. Itano, D.J. Wineland, and P. Gould, Resolved-sideband Raman cooling of a bound atom to the 3D zero-point energy, Phys. Rev. Lett. 75, 4011 (1995).
87Rb
University of Durham
Single-atom addressability
Stimulated Raman transitions.
Single-site addressable.
Single-qubit rotations.
State-selective single atom transport.
Single-atom cooling and detection.
~ 12 µm
~ 5 µm
87Rb
University of Durham
2P3/2
2P1/2
2S1/2
I = 3/210
2P3/2
2P1/2
2S1/2
I = 3/210
2P3/2
2P1/2
2S1/2
I = 3/210
State-selective transport
Left circular 421.1 nm selects 0 Right circular 421.4 nm selects 1
University of Durham
6p 2P
5s 2S1/2
Collisional gates
0 0
Collisionalphase shift
0 1 1 1
0 0 0 1 1 0
1 0
1 1
move
1 0
π/2 π/2
π/2 π/2
π/2π/2
π/2 π/2
move
University of Durham
Magnetically insensitive storage
mF = −2
mF = +1
mF = +2
mF = −1
F = 2
F = 1
Raman selection pulse+ 790.0 nm move beam π/2 π/2
π π
π π
π/2 π/2
0 02P3/2
2P1/2
2S1/2
I = 3/210
University of Durham
0 detection 1 detection
2. Computation
1. Initialisation
3. Read-out
Scalable neutral atom quantum computer
University of Durham
Detection is not state specific but transport is!
University of Durham
Lifetime 6.5 s pressure limited
CO2 trap experiment
Solder seal windows
1. Hard solder: melting point 309 oC2. Tested to 275 oC.3. Reusable.4. Flexibility: high optical quality, any substrate, any coating.5. ZnSe saving − £750 per window!
1st baking cycle at 2.3 Nm
2nd baking cycle at 2.5 Nm
Ultimate pressure of pumping station
S. G. Cox et al. Rev. Sci. Instrum. 74, 1311 (2003); K. J. Weatherill et. al. in preparation
University of Durham
Pyramid MOT10-9 Torr
Science MOT10-11 Torr
Cold atom beam
Largediameter
laser beam
3D chamberUniversity of Durham
An optical lattice with single lattice site optical control for quantum engineeringR Scheunemann, F S Cataliotti, T W Hänsch and M Weitz, J. Opt. B 2, 645 (2000).
Loading CO2 lattices
CO2
CO2+Nd:YAG
University of Durham
CO2Nd:YAG
1D lattice
BEC at one site: - reservoir for extracting single atoms
1. State-selective (site-specific) transport:blue detuning: low scattering
high trap frequencyfaster gates
magnetically insensitive storage.
1. Collisional interactions: slow (not switchable) motional decoherence.
Disadvantages: CO2 laser
University of Durham
Advantages: single-site addressable
3D CO2 trap collisional gates
G.M. Lankhuijzen and L.D. Noordam, Phys. Rev. Lett. 74, 355 (1995).
350260040
53080030
82040025
161016020
502.55015
Γ (x 2π kHz)τ (µs)Vdd(kHz)n
43
0
21dd 4
nrddV ∝=
πε 31n
∝τ
Γ> 100ddV
D. Jaksch, J.I. Cirac, P. Zoller, S.L. Rolston, R. Cote, M.D. Lukin, Fast quantum gates for neutral atoms, Phys. Rev. Lett. 85, 2208 (2000).
780 nm
483 nm
100.01τ (µs)
5x1045x105I (Wcm-2)
1625n
1.0610.6λ (µm)
Ionisation rate
R. M. Potvliege, private communication
University of Durham Rydberg gates
~ 10 µm
Low decoherenceUniversity of Durham
Photon scattering rate for a trap frequency of 1 MHz
25 s-1 at 790 nm!
Nd:YAG
CO2
0.0002 s-1 at 450 nm!
0.002s-1
Rb5p6p7p
5p
6p
5s
7p
Far redFar blue
‘Blue’‘Red’
2
0
41
10~ −
Uωh0
- U0
0
428 nm
13d
More blue!University of Durham
Davidson, Lee, Adams, Kasevich, and S. Chu, PRL. 74, 1311 (1995).
4 s Ramsey fringes!
Rb model potential calculation
R.M. Potvliege and C.S. Adams, preprint
13d
10d
5s
10d
428 nm
Rydion ττ >
Magic Rydberg lattice488 nm 514 nm
Long coherence
University of Durham 428 nm lattice proposal
R.M. Potvliege and C.S. Adams, preprint
2P3/2
2P1/2
2S1/2
I = 3/210
0 detection 1 detection
1. Doubled 856 nm: 3 orthogonal beam pairs.phase stable
2. Mott insulator
3. Local addressing with a ‘pointer’
4. Transfer to expandable lattice + state selective transport to perform read-out
T. Calarco et al. quant-ph/0403197
428 nm428 nm
421 nm
6p 2P
125 mW in 50 µm
100 kHz
Optical lattices: scalability
Low decoherenceFar-red Far-blue
3D CO2 single-site addressable
Switchable interactions
State-selective single-atom conveyor
Collisional gates
Experiment
Magic Rydberg lattice
ConclusionsUniversity of Durham
Scalable up to 103 qubits
Spatially discriminated parallel read-out
Acknowledgements
Collaborators: Robert Potvliege (Rydberg theory)
Graduate students: Paul GriffinKevin WeatherillMatt Pritchard
Research assistants: Simon Cox (up to 08/04)
Collaborators: Erling Riis (Strathclyde)Ifan Hughes, Simon Cornish
Technical support: Robert Wylie (Strathclyde)
Financial support: Previously EPSRC
http://massey.dur.ac.uk/
University of Durham