Readout of superconducting flux qubit Hideaki Takayanagi 髙髙 髙髙 NTT Basic Research Laboratories H. Tanaka, S. Saito, H. Nak H. Tanaka, S. Saito, H. Nak J. Johansson, F. Deppe, J. Johansson, F. Deppe, T.Kutsuzawa,and K. Semba T.Kutsuzawa,and K. Semba NTT Basic Research Labs. Tokyo University of Scien CREST JST M. Ueda M. Ueda Tokyo Institute of Technol M. Thorwart M. Thorwart Heinrich Heine University D. Haviland D. Haviland KTH ers : Nakano (Berry Phase) Johansson ( Vacuum Rabi) Frontiers in Quantum Nanoscience A Sir Mark Oliphant & PITP Conference Noosa Blue Resort, 24 January 2006
Frontiers in Quantum Nanoscience A Sir Mark Oliphant & PITP Conference Noosa Blue Resort, 24 January 2006. Readout of superconducting flux qubits. Hideaki Takayanagi 髙柳 英明 NTT Basic Research Laboratories. H. Tanaka, S. Saito, H. Nakano, J. Johansson, F. Deppe, - PowerPoint PPT Presentation
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Readout of superconducting flux qubits
Hideaki Takayanagi 髙柳 英明NTT Basic Research Laboratories
H. Tanaka, S. Saito, H. Nakano, H. Tanaka, S. Saito, H. Nakano, J. Johansson, F. Deppe, J. Johansson, F. Deppe, T.Kutsuzawa,and K. SembaT.Kutsuzawa,and K. Semba NTT Basic Research Labs. Tokyo University of Science CREST JSTM. UedaM. Ueda Tokyo Institute of TechnologyM. ThorwartM. Thorwart Heinrich Heine UniversityD. HavilandD. Haviland KTH
Posters : Nakano (Berry Phase) Johansson ( Vacuum Rabi)
Frontiers in Quantum NanoscienceA Sir Mark Oliphant & PITP ConferenceNoosa Blue Resort, 24 January 2006
Sample size Sample size ~~ μm μm
Loop sizeLoop size SQUIDSQUID ~ 7 ~ 7 x 7 x 7 mm22
Multi-photon transition betweenMulti-photon transition between superposition of macroscopic quantum states superposition of macroscopic quantum states
E 0
(1)
1.5101.5051.5001.4951.490
qubit
/
h
< I
P >
T
1.5101.5051.5001.4951.490
qubit
/
1 1
1
12
3
32
233
2
2h
+
ー
( ) /√2 ground state
( ) /√2 1st excited state
Multi-photon transition
Macroscopic Quantum state Transition induced by energy difference of single photon.Macroscopic Quantum state Transition induced by energy difference of single photon.Any superposition state can be prepared by adjusting a duration of resonant MW-pulse.Any superposition state can be prepared by adjusting a duration of resonant MW-pulse.
Advantage of Phase shift methodAdvantage of Phase shift method
1SWP
]mod[ 12tR
URF
URF
Vext
|1>
|0>
Read out voltage
T=25mK
0
1π/2Pulse
⊿ t12
π/2Pulse
ensemble :1 0,000
Ψ
Measurement schemeMeasurement scheme
33 . Fast Oscillation. Fast Oscillation
Dephasing time1.84[ns]
Resonant Frequancy11.4 [GHz]
Frequancy by fitting11.18±0.01 [GHz]
π/2 pulse => 5 [ns]
50
45
40
35
30
Psw
[%
]
2. 01. 81. 61. 41. 21. 0 t12 [ns]
Av : 10,000 times
⊿Φ =0 ⊿Φ = π⊿Φ = π/2 ⊿Φ = 3π/2
TPhaseShift=89 ps
• We succeeded in observing Larmor precession ( 11.4 GHz )We succeeded in observing Larmor precession ( 11.4 GHz ) of a flux qubit with phase shifted double pulse method.of a flux qubit with phase shifted double pulse method. An arbitrary unitary transformation of a single qubit is possible.An arbitrary unitary transformation of a single qubit is possible.
・ ・ AdvantageAdvantage
>> We can control qubit phase rapidly ( ~ 10 GHz ).We can control qubit phase rapidly ( ~ 10 GHz ). → → We can save time for each quantum-gate operationWe can save time for each quantum-gate operation → → Compared with the detuning method (~ 0.1 GHz ), Compared with the detuning method (~ 0.1 GHz ), 10 10 ~ ~ 100 times many gates can be implemented.100 times many gates can be implemented.
Artificial Atom in a Cavity
Cavity QED
A. Wallraff et al, Nature 431, 162 (2004)I. Chiorescu et al, Nature 431, 159 (2004)
I I qubitqubit, , LC-oscillator LC-oscillator >> Vacuum Rabi : measurement schemeVacuum Rabi : measurement scheme
Vacuum Rabi oscillationsVacuum Rabi oscillationsDirect evidence of level quantization in a 0.1 mm large
superconducting macroscopic LC -circuit
J. Johansson et al., submitted
Influence of higher level occupationInfluence of higher level occupation
J. Johansson et al., submitted
connection to cavity QEDconnection to cavity QED
qubit 1qubit 1 qubit qubit 22
・・・・・・・・・・・・
・・・・・・
: Josephson junction
Control signal : RF line
readoutSQUID
for qubit 2
qubit 2qubit 2
LC-resonator as a qubit coupler
Multi qubit operation schemeMulti qubit operation scheme
readoutSQUIDfor
qubit 1
qubit 1qubit 1
Harmonic oscillator
Map Map-1
qubit 1
harmonic oscillator
qubit 2
( b1 )0
( b1 )
(c)
0
(c)
( b2 )0
( b2 )√
qubit 1
qubit 2
|g, 0> |g, 1>
|g, 2>
|e, 0> |e, 1>
|e, 2>
(a)(a)
(b)(b)
(c)
( b2 )0
( b2 )√
phaseangle
Coupled Flux QubitsCoupled Flux Qubits
•Multi-photon Rabi oscillationMulti-photon Rabi oscillation - between Macroscopically distinct states- between Macroscopically distinct states
• Faster (Faster (,,-control -control To make best use of the coherence timeTo make best use of the coherence time
- - -control : Rabi with strong driving -control : Rabi with strong driving - - -control by composite pulse : Z(-control by composite pulse : Z()=X()=X(/2)Y(/2)Y()X(-)X(-/2)/2)
• Coupling between qubit and LC-oscillatorCoupling between qubit and LC-oscillator - Conditional spectroscopy of the coupled system - Conditional spectroscopy of the coupled system - Entanglement with an external oscillator- Entanglement with an external oscillator - - Vacuum Rabi oscillationsVacuum Rabi oscillations• Generation of “two qubit”-like states Generation of “two qubit”-like states
|00|00 + + |11|11 andand |01|01 + + |10|10
SummarySummary
Flux-qubit, Atom chip team at NTT-BRL Atsugi
MS+S2006 at NTT AtsugiFebruary 27-March 2, 2006
Int. Symp. on Mesoscopic Superconductivity & Spintronics