超伝導量子ビットのコヒーレンスに対する電離放射線の影響
Antti P Vepsäläinen1, Amir H Karamlou2, John L Orrell3
1Massachusetts Institute of Technology, Cambridge, MA, USA. avepsala@mit.edu.
Nature
|August 28, 2020
まとめ
宇宙線や放射性物質からの電離放射線は 超伝導クビットの準粒子密度を大幅に増加させます 放射線シールドは 量子ビットのコヒーレンス時間を改善できます これは将来の 容認性量子コンピュータにとって 極めて重要です
科学分野:
- 量子コンピューティング
- 超伝導量子装置
- 固体物理学
背景:
- 超伝導量子ビットは 量子テクノロジーの主要なプラットフォームであり 長いコヒーレンス時間と 高精度な操作が必要です
- 超伝導量子ビットのコヘランスは クーパーペアである準粒子によって制限されます
- 実験的に観測された準粒子密度は,赤外線光子が寄与するが,過剰を完全に説明しない,均衡理論によって予測されたより大きい数量である.
研究 の 目的:
- 超伝導量子ビットの高密度準粒子に 欠けているメカニズムを特定する
- 準粒子生成における電離放射線の役割を調査する.
- キュービット性能に対する 放射線シールドの影響を評価する
主な方法:
- 超伝導クビットにおける準粒子密度の実験測定
- 制御された電離放射線源 (環境放射性物質,宇宙線) への曝露
- 放射線シールドの導入とエネルギー放緩時間の変化の測定
主要な成果:
- イオン化放射線が高密度準粒子に大きく寄与する証拠がある.
- この高密度は,現在の量子ビット設計のコヒーレンス時間をミリ秒に制限することを予測しています.
- 放射線シールドは電離放射線の流れを減らし,エネルギー放緩時間を増加させることが実証された.
結論:
- 電子化放射線は 超伝導量子ビットの性能に影響を及ぼす 極めて重要で かつては過小評価されていた要因です
- 誤差を許容する量子計算に必要なコヒーレンス時間を達成するために,電離放射線を緩和することが不可欠です.
- 放射線シールドは量子ビットの一貫性を改善する 有効な方法です
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