contents
DESCRIPTION
past deliverables and present work. HMI. FU-Berlin. decoherence in solid state N/P@C 60. http://www.hmi.de/people/carola.meyer/Dissertation. (defence: 14. November). contents. Micro resonator:. Small amounts (~ 5 mg) of quality 10 -3 have been supplied to Uni Dortmund. stability tests:. - PowerPoint PPT PresentationTRANSCRIPT
Universität Stuttgart, 9. October 2004
contents
• past deliverables and present work
• decoherence in solid state N/P@C60
HMI FU-Berlin
http://www.hmi.de/people/carola.meyer/Dissertation
(defence: 14. November)
Universität Stuttgart, 9. October 2004
material supply (D 1.1)
Small amounts (~ 5 mg) of quality 10-3 have been supplied to Uni Dortmund
Micro resonator:
Small amounts (~ 1 mg) of quality 10-4 to Uni Stuttgart
stability tests:
average amounts (~ 0.5 g) of quality 10-4 to Uni Dublin
enrichment:
No further requests have been received from the partners
Universität Stuttgart, 9. October 2004
N@C60 - C60 dimer (D 1.2)
1.0
0.8
0.6
0.4
0.2
0.0
ES
R-S
igna
l (ar
b. u
nits
)
347.5347.0346.5346.0345.5345.0
magnetic field (mT)
K.-P. Dinse
P. Jakes
Universität Stuttgart, 9. October 2004
present/future work
D 1.3 (month 12): highly enriched material (>20%)
• CTA (BmBF) will start middle of October
production and enrichment will stay at HMI until March ‘04
D 1.4 (month 15): diluted doubly-filled dimers
• Postdoc (BmBF) started in September• build-up the production of mechanically synthesised dimer• start chemical route towards dimer• move to FU-Berlin
Universität Stuttgart, 9. October 2004
spin-lattice relaxation
modulation of local B0 causes relaxation
Hrel = Hhf + Hfs + Hdip = IAS + SDS + STR
• strength of interaction
relaxation rate is determined by:
• phonons (DOS), which modulate the interaction
A ~ 140 MHz
D ~ 14 MHz
T ~ 440 kHz
P@C60
A ~ 15 MHz
D ~ 0.5 MHz
T ~ 440 kHz
N@C60
Universität Stuttgart, 9. October 2004
relaxation paths
10-1
100
101
102
103
104
105
106
relax
ation
rate
(Hz)
4 6 810
2 4 6 8100
2 4
temperature (K)
two relaxation rates can be resolved
Universität Stuttgart, 9. October 2004
harmonic oscillator
10-1
100
101
102
103
104
105
106
relax
ation
rate
(Hz)
4 6 810
2 4 6 8100
2 4
temperature (K)
10-6
10-5
10-4
10-3
10-2
10-1
100
a2/(2h) 2(M
Hz 2)
138.4
138.2
138.0
137.8
137.6
137.4
137.2
137.0
hype
rfin
e sp
littin
g (M
Hz)
300250200150100500
temperature (K)
temperature dependence of hyperfine coupling A
T > 35K: harmonic oscillator
T < 35K: acoustic phonons
Universität Stuttgart, 9. October 2004
T < 35 K
relaxation depends only on spin concentration
model for T1
T > 35 K
relaxation larger for P@C60 than for N@C60
4 6 810
2 4 6 8100
2 4
temperature (K)
10-1
100
101
102
103
104
105
106re
laxat
ionra
te(H
z)P@C60
N@C60
Universität Stuttgart, 9. October 2004
T1 and scalability
for a powder sample with 100% spin concentrationT1 ~ 1 ms
oscillator mode Hint max. coupling strength( )
phonon model
SAI a/2h ~ 140 MHzSDS D/2h ~ 14 MHzinternal oscillatorSTR T/2h ~ 440 kHz
harmonic oscillator
STS' a T/2h ~ 50 MHz STS' b T/2h ~ 1 kHzacoustic phonon STR' T/2h ~ 70 kHz
Debye
a spin concentration 100 %b spin concentration of "Phoenix"
Universität Stuttgart, 9. October 2004
spin-spin relaxation
P@C60
N@C60
~ 50 oscillations at room temperature
number of single qubit operations at room temperature
Universität Stuttgart, 9. October 2004
temperature dependence
N@C60:T2 = 14 µs
10-6
10-5
10-4
10-3
10-2
10-1
100
101
rela
xatio
n tim
e (s
)
4 5 6 710
2 3 4 5 6 7100
2 3 4
temperature (K)
P@C60 powder
P@C60:T2 = 14 µs
Universität Stuttgart, 9. October 2004
T2 and scalability
in a sample with random distribution of electron spins:
• T2 itself is temperature independent
• depends on spin concentration
P@C60/C60 T2
1 x10-4 1 µs
2.4 x10-5 14 µs
1 x10-6 28 µs
• high dilution limit T2 = ?
Universität Stuttgart, 9. October 2004
our qubit in contest
Ladd et al., arXiv:quant-ph/0309164 v1 (23.09.03)
number of single-qubit gates: Rabi
T2 ~ 103number of two-qubit gates: J max T2 ~ 103
for error correction gain one order of magnitude in T2:• measure T2 at spin concentrations as low as possible (signal/noise)
• use pulse sesquences known from NMR for dipolar decoupling