arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2409.14735quant-phcond-mat.str-elphysics.comp-ph
收藏

量子点自旋链中的声子退相干、纠缠与仅交换Toffoli门序列

Phonon Dephasing, Entanglement and Exchange-Only Toffoli Gate Sequence in Quantum Dot Spin Chains

Guanjie He

AI总结:

本文系统研究量子点自旋链中的声子退相干、纠缠特性,并利用Krotov最优控制设计仅交换Toffoli门的高效脉冲序列,为量子模拟与量子算法优化提供新方案。

摘要:

量子点自旋链系统对于量子模拟和研究集体电子行为至关重要,因此需要理解其机制与控制协议。第1章介绍关键概念,重点讨论扩展Hubbard模型、双量子点系统以及电子-声子耦合。第2章通过失谐变化探索无偏置和偏置情形下多电子双量子点中的电子-声子耦合。在无偏置情形下,由电子-声子耦合引起的退相干通常随着右量子点中电子数增加而增强;这一趋势在偏置情形下并不一致,表明多电子量子点在某些条件下可能具有潜在优势。第3章研究由扩展Hubbard模型描述的多电子量子点自旋链中的纠缠熵。局域纠缠和两体纠缠受Coulomb相互作用、隧穿强度、电子构型以及格点势能的影响。纠缠图揭示了相变,这些相变显著受到耦合强度比和势能变化的影响;调节特定量子点的势能会关键性地影响基态构型和纠缠熵。第4章受无退相干子空间概念的启发,探索由Heisenberg模型定义的九自旋、九量子点系统中的操作序列,其基矢由总角动量量子数确定。采用Krotov量子最优控制方法,我们为仅交换量子点自旋链确定了一种更高效的脉冲级操作序列,为传统量子门分解提供了更优替代方案,并有望促进更简洁的量子算法表示的发展。

英文摘要:

The quantum dot spin chain system is vital for quantum simulation and studying collective electron behaviors, necessitating an understanding of its mechanisms and control protocols. Chapter 1 introduces key concepts, focusing on the extended Hubbard model, double quantum dot systems, and electron-phonon coupling. Chapter 2 explores electron-phonon coupling in multielectron double quantum dots under unbiased and biased scenarios via detuning variations. In the unbiased case, dephasing due to electron-phonon coupling generally increases with more electrons in the right dot; this trend is inconsistent in the biased case, suggesting potential advantages of multielectron quantum dots under certain conditions. Chapter 3 investigates entanglement entropy in a multielectron quantum dot spin chain described by the extended Hubbard model. Local and pairwise entanglement are influenced by Coulomb interactions, tunneling strengths, electronic configurations, and site potential energies. The entanglement diagram reveals phase transitions significantly impacted by coupling strength ratios and potential energy variations; adjusting the potential energy of a specific dot critically influences ground state configurations and entanglement entropy. Chapter 4, inspired by the decoherence-free subspace concept, explores operation sequences in a nine-spin, nine-quantum-dot system defined by the Heisenberg model, with bases determined by total angular momentum quantum numbers. Employing the Krotov method of quantum optimal control, we identify a more efficient pulse-level operation sequence for an exchange-only quantum dot spin chain, offering a superior alternative to conventional quantum gate decomposition and potentially enhancing the development of more concise quantum algorithm representations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑