High yield, low variability – Employing silicon CMOS technology for the realization of spin qubits

高产量、低变异性 – 采用硅 CMOS 技术实现自旋量子位

• 批准号: 421769186
• 负责人: Professor Dr. Joachim Knoch
• 金额: --
• 依托单位: Institut für Halbleitertechnik (IHT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/421769186?language=en
• 关键词: yield; low; variability; Employing; silicon

In recent years, all building blocks for quantum computation using spin qubits were demonstrated in electrostatically defined spin qubits based on e.g. GaAs or Si. Remaining manipulation infidelities are tolerable by using a surface code which requires a large number of physical qubits. As a result, the feasibility of a spin qubit quantum computer is directly related to the scalability of the system. However, even state-of-the-art qubit realizations rely on a rather immature fabrication technology with very low yield and large device-to-device variability. Furthermore, complex multi-layer gate patterns will be required to improve the confinement potentials and to realize new functionalities e.g. a quantum bus. In the current project a qubit technology will be developed that is based on fabrication techniques derived from industrial silicon CMOS technology ensuring scalability and a high yield of our approach. Due to the low-temperature operation and in order to guarantee tunability of the qubits a very large number of nanoscale gate electrodes will be realized on top of a semiconductor heterostructure in which the single electron spin representing qubits will be defined electrostatically. For the realization of these gate structures we will use the so-called (multiple) spacer process which not only avoids the need for highly sophisticated nanolithography (such as electron-beam lithography). More importantly, it significantly reduces the device-to-device variability. This strongly increases the yield and in addition might even allow a reduction of the total number of gates necessary to electrostatically tune the individual qubits. The fabrication will be carried out with the lowest possible ther-mal budget such that the impact on the heterostructure is minimized (e.g. no reduction of valley splitting in Si/SiGe quantum wells) and that the developed technology can be used for different substrates such as GaAs/AlGaAs.Throughout the project MBE-grown Si/SiGe multi-quantum dot samples will be fabricated. The gate-tunability of the quantum dots, the electrostatic noise and the valley splitting are determined by transport measurements at ~20 mK. Qubit functionality such as charge-readout by an adjacent read-out quantum dot and spin-to-charge conversion will be demonstrated. Within the project we aim at extending the number of quantum dots to 40 without losing tunability and functionality of each quantum dot. The multi-quantum dot samples allow mapping the valley splitting variability over a large area. Combining the development of appropriate fabrication technologies to facilitate groundbreaking work on multi quantum dot/qubit devices our approach has the potential to provide highly relevant contributions to the science and technology of the field. Furthermore, since the technology devel-opment will be as close as possible to current industrial processes it may help accelerating the realization of future quantum information processors.

近些年来，利用自旋量子比特进行量子计算的所有构件都是在基于GaAs或Si的静电定义的自旋量子比特中被证明的。通过使用需要大量物理量子比特的表面代码，剩余的操作不保真是可以容忍的。因此，自旋量子比特量子计算机的可行性直接关系到系统的可扩展性。然而，即使是最先进的量子比特实现也依赖于相当不成熟的制造技术，成品率非常低，设备到设备的可变性很大。此外，需要复杂的多层栅极图案来改善限制势并实现新的功能，如量子总线。在当前的项目中，我们将开发一种量子比特技术，该技术基于源于工业硅CMOS工艺的制造技术，以确保我们方法的可扩展性和高产率。由于工作温度低，为了保证量子比特的可调性，将在半导体异质结上实现大量的纳米级栅电极，其中代表量子比特的单电子自旋将被静电定义。为了实现这些栅极结构，我们将使用所谓的(多)间隔层工艺，它不仅避免了对高度复杂的纳米光刻(如电子束光刻)的需要。更重要的是，它显著降低了设备到设备的可变性。这极大地提高了产量，此外，还可能减少对单个量子比特进行静电调节所需的门的总数。该工艺将以尽可能低的热预算进行，以使对异质结构的影响最小化(例如，不会减少Si/SiGe量子阱中的山谷分裂)，并且所开发的技术可以用于不同的衬底，例如，GaAs/AlGaAs。通过该项目，我们将制备MBE生长的Si/SiGe多量子点样品。通过在~20mK的输运测量，确定了量子点的栅可调谐、静电噪声和能谷分裂。将演示量子比特功能，如通过相邻读出的量子点进行电荷读出和自旋到电荷的转换。在该项目中，我们的目标是在不损失每个量子点的可调性和功能性的情况下，将量子点的数量扩大到40个。多量子点样本允许在大范围内绘制山谷分裂的可变性。结合开发合适的制造技术来促进多量子点/量子比特器件的开创性工作，我们的方法有可能为该领域的科学和技术做出高度相关的贡献。此外，由于技术的发展将尽可能接近当前的工业过程，这可能有助于加速实现未来的量子信息处理器。