Study on quantum-state manipulation and quantum coherence in small-Josephson-junction devices

2014 Fiscal Year Final Research Report

• Project/Area Number: 24540317
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics I
• Research Institution: Yokohama National University
• Principal Investigator: SHIMAZU Yoshihiro 横浜国立大学, 工学(系)研究科(研究院), 准教授 (70235612)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: ジョセフソン接合 / 超伝導デバイス / 量子ビット / 量子コンピュータ / 量子コヒーレンス

Outline of Final Research Achievements

Superconducting qubits consisting of ultrasmall Josephson junctions have attracted much interest for the implementation of a scalable quantum computer. We investigated a superconducting flux qubit strongly coupled to a DC-SQUID that is used for readout of the qubit. Higher-order red and blue sideband transitions were clearly observed in spectroscopic measurement. The origin of these transitions was found to be a SQUID plasma mode. Manipulation of the quantum states was demonstrated as Rabi oscillations on the carrier transition and sideband transitions. The observation of the sidebands up to |M| = 3, where M represents the change in the quantum number of the resonator state, is consistent with the calculated transition matrix elements between the quantum states of the coupled system. Our results may provide a basis for future experiments manipulating many composite levels, including demonstration of quantum gates using sideband transitions.

Free Research Field

低温物性実験