Quantum Information and Metrology with RF Traps at NIST
D. J. Wineland, NIST, Boulder, CO
NIST- Boulder ions:
J. Amini (PostDoc, Berkeley)‡
J. C. Bergquist (NIST)
S. Bickman (PostDoc, Yale) &
M. Biercuk (GTRI) %
R. B. Blakestad (student, CU)♣
J. J. Bollinger (NIST)
R. Bowler (student, CU)
J. Britton (PostDoc, CU)
K. Brown (PostDoc, U. Md.)
J. Chou (PostDoc, Cal Tech)
Y. Colombe (PostDoc, ENS)
D. Hanneke (PostDoc, Harvard)
J. Home (PostDoc, Oxford) @
D. Hume (student, CU) †
W. Itano (NIST)
T –R Tan (Student, CU)
J. D. Jost (PostDoc, CU)
M. Thorpe (PostDoc, CU)
E. Knill (NIST)*
H. Uys (PostDoc, U. Arizona) #
D. Leibfried (NIST)
A. VanDevender (PD, U. Illinois)
D. Leibrandt (PostDoc, MIT) U. Warring (PD, Heidelberg)
Y. Lin (student , CU)
A. Wilson (guest researcher)
C. Ospelkaus (PD, Hamburg) D. J. Wineland (NIST)
T. Rosenband (NIST)
J. Yao (student , CU)
* NIST computation division, Boulder
† Current address: Optical freq. meas. group, NIST
‡ Current address: Georgia Tech. Res. Inst.
# Current address: CSIR, South Africa
% Current address: University of Sydney
& Current address: Vescent Photonics, Denver
@ Current address: ETH, Zürich
♣ Current address: JQI, U. Md.
Summary:
• scaling to larger systems (increase fidelity and number)
- best 2-qubit gates (Innsbruck) ε < 0.01
- ion arrays
* transporting quantum information
* trap fabrication & steps toward simulation
* qubit detection (integrated optics)
* low-temperature traps
* scaling with gates
- alternate strategies?, e.g., microwave gates
• metrology, e.g. atomic clocks
• prospects
Multiplexed trap arrays
Scale up?
a+b
a
artiste: D. Leibfried
-10
-5
0
c
axial modes only
-15
d
b
a
carrier
2a
40
20
2b,a+c
c-a
b-a
b-a
2b,a+c
d
a+b
c
2a
b
c-a
60
b+c
Fluorescence counts
Mode competition –
example: axial modes, N = 4 ions
b+c
a (C.O.M.)
b (stretch)
c (Egyptian)
d (stretch-2)
5
Raman Detuning δR (MHz)
10
15
mode
amplitudes
Examples:
Linear arrays:
NIST (M. Rowe et al.,
Quant. Inf. Comp. 2, 257 (2002))
S. A. Schulz et al., New J. Phys. 10, 045007 (2008)
Schmidt-Kaler group
Traps with junctions (2-D):
W. Hensinger et al., (Monroe group)
Appl. Phys. Lett. 88, 034101 (2006)
R. Blakestad et al., (NIST)
PRL 102, 153002 (2009)
Pseudopotential near junction
0.3
eV
Maxwell:
harmonic confinement
⇒ pseudopotential bumps
(J. H. Wesenberg, PRA 78, 063410 (2008))
• primary
mechanisms
identified
(R.heating
Blakestad
et al.,
◊ PRL
RF noise
at ΩRF(2009))
± ωz
102, 153002
◊ DAC updating rate
• heating < 1 quantum/transfer
(R. Blakestad et al.,
PRL 102, 153002 (2009))
Surface-electrode traps
• repeatable component library
• two-layer construction with vias
• “backside” loading
• transport in linear sections and through “Y” junctions
Gold on
Quartz
1 mm
~150 zone “racetrack”
(J. Amini et al. New J. Phys. 12, 033031 (2010))
Surface traps ⇒ one route to complex simulations
More general Heisenberg/Ising-type couplings :
like two qubit-gates
R. Schmied, J. Wesenberg,
D. Leibfried
PRL 102, 233002 (2009)
Integrated Optics
Problem with ions: charging of optics
evaporated gold
quartz substrate
quartz fiber NA = 0.37, 2.1% collection
η(fiber) = 0.3 x η(multi-element lens, NA = 0.5)
photo
Control height
with differential RF
Aaron VanDevender, Yves Colombe et al.,
PRL 105, 023001 (2010)
(in collaboration with Sandia National Labs)
Cold Trap (4 K)
Kenton Brown, Christian Ospelkaus, Yves Colombe, Andrew Wilson
LHe Reservoir
Radiation shield
Ion trap
Laser beam ports
Schwarzschild (reflective)
imaging optics
vacuum “Pillbox”
(bake at 150° C)
CCD and detection (PMT)
~ 20 cm
•ion lifetime → ∞
((Be+)*+ H2 → BeH+ + H apparently eliminated)
• good (RF) qubit flopping
(F = 2,mF = -2〉 ↔ |F = 1,mF = -1〉)
after ~ 500 flops
8
6
5-zone test trap
4
(Au on X-tal
quartz)
2
0
40 µm
25
50
75
100
4900 4925 4950 4975 5000
τ (µs) →
(backside illumination)
Low heating
(sometimes)
SE(ω): spectral density
of electric-field fluctuations
Be+, Mg+ (NIST)
GaAS
U. Mich.
Cadmium T = 150 K U. Mich.
Strontium @ T = 4 K (MIT)
surface
electrode
traps
⊗
X-trap
NIST 4 K
surface trap
Deslauriers et al. PRL 97 (2006) and R. J. Epstein, et al. PRA 76 033411-1 (2007)
Coupling ions in separate wells
τexchange
d
∝ d3
• generalization of quantum-logic spectroscopy
(D. Heinzen, DJW, PRA 42 2977 (1990))
• step towards coupling to other quantum systems
• new entanglement schemes
• precursor to arrays for simulation
40 µm
5-zone “4-wire” surface-electrode
test trap (Au on crystaline quartz)
trap photo,
PPT ions
T≅4K
(e.g. Schmied, Wesenberg, Leibfried PRL 102, 233002 (09))
(backside illumination)
4.125
4.12
4.115
4.11
Be+ ions, d = 40 µm,
fz = 4.1 MHz
6
3 kHz
thermal state transfer
〈n〉 destination ion
〈n〉
3
4.105
τcoupling(µs) →
4.1
400
800
Scaling with gates
Scale up?
a (C.O.M.)
b (stretch)
c (Egyptian)
axial modes only
qubit ion
refrigerator
-15 ion -10
-5
0
d
2a
c
carrier
b
9Be+
a
24Mg+
b+c
a+b
qubit “packet”
a
40
2b,a+c
c-a
d (stretch-2)
b-a
b-a
2b,a+c
d
a+b
c
2a
b
c-a
60
b+c
Fluorescence counts
Mode competition –
example: axial modes, N = 4 ions
20
5
Raman Detuning δR (MHz)
10
15
mode
amplitudes
“hybrid” qubit system
|F, mF〉
9Be+ 2S
1/2
~1.0 GHz
Hyperfine levels
B = 119.64 G
103
MHz
69 MHz
“hybrid” qubit system
qubit for memory,
transport, rotations
Magnetic-fieldindependent manifold
Coherence time ~ 15 s
C. Langer, et al, Phys. Rev. Lett. 95 060502 (2005)
“hybrid” qubit system
qubit for
two-qubit
(phase) gates
Programmable (universal) 2-qubit quantum processor
(David Hanneke, Jonathan Home, John Jost et al., Nature Physics 6, 13 (2010).)
Theory: arbitrary unitary U (SU4):
B. Kraus and J. I. Cirac, Phys. Rev. A 63 062309 (2001)
V. V. Shende, et al, Phys. Rev. A 69 062321 (2004)
qubit 1
qubit 2
Experiment:
phase gates
A
B
plus,
laser cooling
160 randomly chosen operators U,
apply to
average final state fidelity = 79.1(4.5)
extension: entangled mechanical oscillators
240 μm
A
4 μm
B
John Jost, Jonathan Home, Jason Amini, David Hanneke et al., Nature, 459, 683 (2009)
Alternateive strategies: RF magnetic field gates?
Why? Get rid of the lasers!
static magnetic field gradient:
Wunderlich group (Siegen):
Adv. At. Mol. Opt. Phys. 49, 295 (2003)
M. Johanning et al., PRL 102, 073004 (2009)
Chuang group (MIT):
S. Wang et al., Appl. Phys. Lett. 94, 094103 (2009)
Meschede group (Bonn):
L. Förster et al., PRL 103, 233001 (2009)
AC magnetic field gradient
Dehmelt – g-2 “AC Stern Gerlach effect”
NIST:
Christian Ospelkaus et al., PRL 101, 090502 (2008)
“5-wire” surface-electrode trap
(Christian Ospelkaus, Ulrich Warring, …)
τπ ~ 20 ns
(2,-2)
(2,-1)
(2,0)
(2,+1)
25Mg+
0.02
0.04
τ(µs) →
~1.7 GHz
(field independent, B ≅ 220 gauss)
(F,mF)
40 µm
(3,+1)
Trap RF
(3,-1)
Trap RF
(3,0)
(3,-2)
(3,-3)
Lamb-Dicke parameter η ~ 1/3000
trap photo,
PPT ion
Applications to metrology: Al+ “quantum-logic clock”
(James Chou, David Hume, Mike Thorpe, Till Rosenband )
1P
1
Coulomb
interaction
2P
3/2
3P
0
Al+
optical
qubit
λ = 167 nm
λ = 267 nm
1S
0
(F=1, mF = -1)
2S
1/2
Be+
hyperfine
qubit
→ motion →
(F=2, mF = -2)
Shopping list:
• “More and better”
♦ reduce gate errors further
♦ scale to many qubits
• couple ion qubits to other quantum systems
* e.g., macroscopic systems
• simulations, applications in spectroscopy
• smaller structures ⇒ everything gets better
♦ but, solve heating problem!
Ion “trapology” workshop (NIST Boulder, February 16, 17, 2011))
NIST- Boulder ions:
J. Amini (Postdoc, Berkeley)‡
J. C. Bergquist (NIST)
S. Bickman (PD, Yale) &
M. Biercuk (GTRI) %
R. B. Blakestad (student, CU)♣
J. J. Bollinger (NIST)
R. Bowler (student, CU)
J. Britton (Postdoc, CU)
K. Brown (Postdoc, U. Md.)
J. Chou (Postdoc, Cal Tech)
Y. Colombe (Postdoc, ENS)
D. Hanneke (Postdoc, Harvard)
J. Home (Postdoc, Oxford) @
D. Hume (student, CU) †
T –R Tan (Student, CU)
W. Itano (NIST)
M. Thorpe (PD, CU)
J. D. Jost (Postdoc, CU)
H. Uys (Postdoc, U. Arizona) #
E. Knill (NIST)*
A. VanDevender (PD, U. Illinois)
D. Leibfried (NIST)
U. Warring (PD, Heidelberg)
D. Leibrandt (PD, MIT)
A. Wilson (guest researcher)
Y. Lin (student , CU)
C. Ospelkaus (PD, Hamburg) D. J. Wineland (NIST)
J. Yao (student , CU)
T. Rosenband (NIST)
* NIST computation division, Boulder
† Current address: Optical freq. meas. group, NIST
‡ Current address: Georgia Tech Res. Inst.
# Current address: CSIR, South Africa
% Current address: University of Sydney
& Current address: Vescent Photonics, Denver
@ Current address: ETH, Zürich
♣ Current address: JQI, U. Md.