Electron spin coherence exceeding seconds in high purity silicon
Alexei M. Tyryshkin, Shinichi Tojo, John J. L. Morton, Helge Riemann, Nikolai V. Abrosimov, Peter Becker, Hans-Joachim Pohl, Thomas Schenkel, Michael L. W. Thew… 展开作者
Alexei M. Tyryshkin, Shinichi Tojo, John J. L. Morton, Helge Riemann, Nikolai V. Abrosimov, Peter Becker, Hans-Joachim Pohl, Thomas Schenkel, Michael L. W. Thewalt, Kohei M. Itoh, S. A. Lyon
Silicon is undoubtedly one of the most promising semiconductor materials for spin-based information processing devices. Its highly advanced fabrication technology facilitates the transition from individual devices to large-scale processors, and the availability of an isotopically-purified $^{28}$Si form with no magnetic nuclei overcomes what is a main source of spin decoherence in many other materials. Nevertheless, the coherence lifetimes of electron spins in the solid state have typically remained several orders of magnitude lower than what can be achieved in isolated high-vacuum systems such as trapped ions. Here we examine electron spin coherence of donors in very pure $^{28}$Si material, with a residual $^{29}$Si concentration of less than 50 ppm and donor densities of $10^{14-15}$ per cm$^3$. We elucidate three separate mechanisms for spin decoherence, active at different temperatures, and extract a coherence lifetime $T_2$ up to 2 seconds. In this regime, we find the electron spin is sensitive to interactions with other donor electron spins separated by ~200 nm. We apply a magnetic field gradient in order to suppress such interactions and obtain an extrapolated electron spin $T_2$ of 10 seconds at 1.8 K. These coherence lifetimes are without peer in the solid state by several orders of magnitude and comparable with high-vacuum qubits, making electron spins of donors in silicon ideal components of a quantum computer, or quantum memories for systems such as superconducting qubits.
99.992 % $^{28}$Si CVD-grown epilayer on 300 mm substrates for large scale integration of silicon spin qubits
硅基量子比特在量子点中具有电子自旋或在掺杂剂上具有核自旋，是量子计算竞赛中的有力竞争者。除了工艺集成成熟度之外，在用于量子位的最丰富的$^{28}$硅同位素主晶体中缺乏核自旋是这种硅量子技术的主要资产。我们在300 mm天然丰度硅晶体上生长了同位素纯度大于99.992%的$^{28}$硅外延层（外延层）。单晶同位素纯化外延层的质量符合与我们的工业前CMOS设施中使用的天然外延层相同的严格质量要求。同位素纯化的衬底现在已经准备好使用最先进的300 mm Si CMOS铸造设备和工艺制造硅量子比特
High-field Spatial Imaging of Charge Transport in Silicon at Low Temperature
我们提出了在5 K和500 mK的温度下，通过1 cm × 1 cm × 4 mm厚的高纯硅晶体（$\sim$ 15 k $Ω$ -cm）的电荷输运的直接成像测量。我们使用这些数据来测量电子和空穴的横向扩散作为沿[111]晶轴施加的电场的函数，并验证我们的低温Monte Carlo软件。本文中的场强范围超过了先前研究（DOI：10.1063/1.5049691）中使用的场强范围10倍，现在包括了最近一些硅暗物质探测器工作的区域（DOI：10.1103/PhysRevLett.121.051301）。我们还报告了表面电荷捕获的现象，可以减少预期的电荷收集。
Non-volatile programmable silicon photonics using an ultralow loss Sb$_2$Se$_3$ phase change material
可适应、可重构和可编程是下一代硅基光子处理器、神经网络和量子网络的关键功能。相变技术提供了经验证的非易失性电子可编程性，然而迄今为止使用的材料已经显示出与集成光子平台不兼容的过高的光学损耗。在这里，我们证明了以前未开发的材料Sb $_2$ Se $_3$的超低损耗可编程硅光子的能力。在Sb $_2$ Se $_3$中看到的大折射率对比度和超低损耗的有利组合促进了马赫-曾德尔干涉仪中超过10 $π$弧度的前所未有的光学相位控制。为了证明对光的流动的完全控制，我们引入纳米光子数字图案化作为一种概念上的新方法，其足迹数量级小于最先进的干涉仪网格。我们的方法使大量的可能性，在高密度的硅芯片上的光学功能的重新配置。
Silicon Solar Cell Design for >30% Efficiency via Singlet Fission
University of New South Wales（新南威尔士大学）；Trina Solar（天合光能）；Department of Materials, University of Oxford（牛津大学材料系）；School of Photovoltaic and Renewable Energy Engineering, University of New South Wales（新南威尔士大学光伏与可再生能源工程学院）；State Key Laboratory for Photovoltaic Science and Technology (SKL PVST)（光伏科学与技术国家重点实验室）；School of Chemistry, University of New South Wales（新南威尔士大学化学学院）
