矽基量子點自旋量子位元測量方法的理論分析

Analysis of Readout Measurements for Silicon-based Quantum-dot Spin Qubits

林嗣智(Ssu-Chih Lin)

指導教授 ： 管希聖

國立臺灣大學/理學院/應用物理研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003299

摘要

半導體自旋量子位元是一個有潛力的實現量子電腦的方法，不只是因為它能相容於現今的半導體工業而能規模化，同時在也是因為純化後它在「自旋真空」中有很長的同協時間。但是，長久以來相較於其他固態系統如超導量子位元，它受制於較長的操作與測量時間。此外，現今常用的額外感測器如量子點接觸或單電子電晶體需要置於每個量子位元旁，這會成為規模化時的阻礙。一個解決的方法是將它連接到超導共震器上，而這已經在超導量子系統中作為 ”circuit quantumelectrodynamics” 廣為研究。
在這篇論文中，我們將建立一個完全量子化的模型來分析單重態─三重態量子位元與超導共平面空腔交互作用，並指出量子位元與空腔於 電子態─空腔態共
振、自旋態-空腔態共振、與 E− -空腔態共振的 straddling regime，使得空腔頻率變化量提升或彼此抵消的現象。此外，我們預期輸出結果在正失諧時會比現在常用的參數區間好。然後，我們也用了這個模型來分析三量子點交換量子位元的讀取測量，並可以與最近的實驗結果良好地吻合。

關鍵字

半導體雙量子點 ； 包立自旋封鎖測量 ； Circuit QED

並列摘要

Semiconductor silicon-based spin quibt system is promising platform for quantum computg due to not only its scalability of being compatible to nowadays MOS industry but also its long coherence in the purified ”spin vacuum”. However, it long suffer from longer gate and measurement times than other solid-state systems, like superconductor qubit system. Moreover, the additional measurement electrometers like quantum point contact or single electron transistor used nowadays must be placed nearby every qubits, which will be a burden when scaling up. One of the solution is to connect it to the superconductor resonator, which is widely used in superconductor qubit system and long studied as circuit quantum electrodynamics.
In this thesis, we build a full quantum model of the Singlet-Triplet qubit coupling to the superconductor coplanar cavity and show the straddling regime, where the cavity frequency shift is enhanced or canceled each other, between charge-cavity resonance, spin-cavity resonance, and E− - cavity resonance. Further, the readout performance is predicted to be higher in positive detuning regime contrast to usual one. Besides, we also use this model to deal with the readout measurement of the triple-quantum-dot exchange qubit and the result we obtain fits well with recent experiment result.

並列關鍵字

Semiconductor Double Quantum Dots ； Pauli Spin Blockade Readout ； Circuit QED

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