Application of variable boundary condition in waveguide quantum electrodynamics

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03684
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Tokyo Medical and Dental University
• Principal Investigator: Koshino Kazuki 東京医科歯科大学, 教養部, 准教授 (90332311)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 導波路QED / 超伝導量子計算 / 量子光学 / 量子制御

Outline of Final Research Achievements

When we apply a resonant light to an atom through a waveguide, the atom completely reflects the light if the light intensity is weak. In contrast, the atom completely transmits the light if the light intensity is strong. In other words, an atom changes the boundary condition of a waveguide depending on the intensity of the applied field. Using this property, we proposed a Josephson quantum filter, which resolves the tradeoff between the gate speed and the qubit lifetime, which is universal in superconducting quantum computation.

Free Research Field

量子光学

Academic Significance and Societal Importance of the Research Achievements

集積化された固体量子ビットを用いて量子計算を遂行するためには，個別アクセスのために個々の量子ビットに導波路を結合させ，そこから制御パルスを照射する．ゲート時間を短くするためには量子ビット―導波路結合は強いほうが良いが，量子ビットの寿命を長くするためには量子ビットの導波路への輻射緩和を防ぐ必要があり結合は弱いほうが良い．このように，ゲート時間と量子ビット寿命にはトレードオフの関係がある．本研究で提案したジョセフソン量子フィルタはこのトレードオフを解消するものであり，超伝導量子計算の実現可能性を拡げるものである．