近日，澳大利亚新南威尔士大学的Chih Hwan Yang&Jonathan Y. Huang及其研究团队取得一项新进展。经过不懈努力，他们实现1K以上的高保真自旋量子比特操作和算法初始化。相关研究成果已于2024年3月27日在国际权威学术期刊《自然》上发表。

该研究团队成功在超过1K的硅材料中调整和操作自旋量子比特，并实现了容错操作所需的保真度范围。研究人员设计了一种创新的算法初始化协议，即使在热能远高于量子比特能量的情况下，也能制备出纯净的双量子比特态。结合射频读出技术，他们实现了高达99.34%的读出和初始化保真度。此外，研究人员还展示了单量子比特Clifford门保真度高达99.85%，双量子比特门保真度达到98.92%。这些重要进展突破了热能必须远低于量子比特能量才能实现高保真操作的基本限制，为可扩展和容错量子计算的发展扫清了主要障碍。

据悉，将量子比特编码于半导体自旋载流子中，已被视为一种前景广阔的商业量子计算机方法，具有平版印刷生产和大规模集成的优势。然而，要实现有利的量子应用，必须操作大量的量子比特，这将产生超过毫开尔文温度下低温恒温器所能承受的冷却负荷。随着放大速度的提升，容错操作必须在1K以上的温度进行，此时所需的冷却功率将高出数个数量级。

附：英文原文

Title: High-fidelity spin qubit operation and algorithmic initialization above 1 K

Author: Huang, Jonathan Y., Su, Rocky Y., Lim, Wee Han, Feng, MengKe, van Straaten, Barnaby, Severin, Brandon, Gilbert, Will, Dumoulin Stuyck, Nard, Tanttu, Tuomo, Serrano, Santiago, Cifuentes, Jesus D., Hansen, Ingvild, Seedhouse, Amanda E., Vahapoglu, Ensar, Leon, Ross C. C., Abrosimov, Nikolay V., Pohl, Hans-Joachim, Thewalt, Michael L. W., Hudson, Fay E., Escott, Christopher C., Ares, Natalia, Bartlett, Stephen D., Morello, Andrea, Saraiva, Andre, Laucht, Arne, Dzurak, Andrew S., Yang, Chih Hwan

Issue&Volume: 2024-03-27

Abstract: The encoding of qubits in semiconductor spin carriers has been recognized as a promising approach to a commercial quantum computer that can be lithographically produced and integrated at scale. However, the operation of the large number of qubits required for advantageous quantum applications will produce a thermal load exceeding the available cooling power of cryostats at millikelvin temperatures. As the scale-up accelerates, it becomes imperative to establish fault-tolerant operation above 1K, at which the cooling power is orders of magnitude higher. Here we tune up and operate spin qubits in silicon above 1K, with fidelities in the range required for fault-tolerant operations at these temperatures. We design an algorithmic initialization protocol to prepare a pure two-qubit state even when the thermal energy is substantially above the qubit energies and incorporate radiofrequency readout to achieve fidelities up to 99.34% for both readout and initialization. We also demonstrate single-qubit Clifford gate fidelities up to 99.85% and a two-qubit gate fidelity of 98.92%. These advances overcome the fundamental limitation that the thermal energy must be well below the qubit energies for the high-fidelity operation to be possible, surmounting a main obstacle in the pathway to scalable and fault-tolerant quantum computation.

DOI: 10.1038/s41586-024-07160-2

Source: https://www.nature.com/articles/s41586-024-07160-2