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Shiro Saito1, Xiaobo Zhu1, Robert Amsuss1, Yuichiro Matsuzaki1 , William J. Munro1, Kosuke Kakuyanagi1, Hayato Nakano1, Takaaki Shimooka2, Norikazu Mizuochi2 ,
Kae Nemoto3, and Kouichi Semba 1,3
1 : NTT Basic Research Laboratories, NTT Corporation, 2 : University of Osaka, Graduate school of Engineering Science,
3 : National Institute of Informatics
超伝導・ダイヤモンド複合系におけるメモリー動作
2012年8月16日FIRST夏期研修会 @ 宮古島
1
Outline
1. IntroductionSuperconducting qubitSuperconductor-diamond hybrid system
2. Experiment under zero in-plane magnetic fieldStrong coupling , coherent oscillations
3. Experiment under zero in-plane magnetic fieldlower NV densitycoherence time is improved
4. Summary2
1CJ <EE CJ1 EE<1CJ ≈EE
Type charge quantronium flux
Coherence time 0.5 µs 0.5 µs 23 µs
φ
Charge (NEC)
Quantronium (Saclay)
Flux (Delft)
phase
0.15 µs
transmon
25 µs(95 µs)
CJ1 EE<<
Transmon (Yale)
Phase (UCSB)
3
Superconducting qubits
99 00 01 02 03 04 05 06 07 08 09 10 11 12
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Year
Decoherence tim
e (s)
Based on J.S.Tsai’s plot, NTT’s data and the newest data are added.
Coherence time of superconducting qubits
NEC Off-OB + EchoCharge
SaclayOB Quantronium MIT/NEC
OB+EchoFlux
NTT OB+EchoFlux
NEC / RIKEN OB+EchoFlux
NEC Off-OBCharge
Delft / NTT OB+EchoFlux
Delft / NEC OffOB+EchoFlux
Yale univ.Transmon
in 3D cavity
IBMTransmon
in 3D cavity
Best data
T1 : 70 µs
T2Ramsey: 95 µs
∆ : 4.2 GHz
EchoRamsey
Energy spectrum
Optimal Bias (OB)
4
Quantum bit :
Processor + memory(superconducting device)
CPU: processor(semiconductor device)
Conventional computer
RAM: memory
(semiconductor device)
Quantum computer using superconductor
?
Components of Computers
5
① Long T2 at RT: 1.8 ms→ suitable for a memory
② B=0 Ground state splitting : 2.88 GHz → idealistic to couple to a superconducting qubit
③ coexistence of GHz (2.88 GHz) and sub-PHz transitions : 638 nm (0.47 PHz)
→ microwave ⇔ optical freq region : Quantum Frequency Converter / Transducer
PL : 638 nm
Microwave Compatible with superconducting qubit
Telecomunicationwavelength (QKD)
● coexistence of GHz and sub-PHz transitions
NV- center
~ ms coherence time at RT
G. Balasubramanian, et al., Nature material, 8, 383 (2009)
6
MW-resonator ⇔NV-diamondFlux-qubit ⇔NV-diamond
Superconducting circuits and spin ensembles
Transmon-qubit ⇔ MW-resonator ⇔NV-diamond
γκ ,singleens >>= Ngg MHz 22ens =g
Hz 22sigle =g1210=NY. Kubo, et al., PRL 105, 140502 (2010)