近日，美国威斯康星大学麦迪逊分校的Robert Joynt及其研究团队取得一项新进展。经过不懈努力，他们利用两能级系统的随机共振提高量子比特相干时间。相关研究成果已于2024年11月5日在国际知名学术期刊《物理评论A》上发表。

该研究团队提出一种在这两个问题上都取得进展的方法。当对两能级系统（TLS）施加振荡场时，会发生随机共振，噪声频谱会移至更高频率。这种TLS噪声频谱的转移将增加它们所影响的量子比特的退相干时间。

此外，这种效应的细节取决于噪声源的物理特性。因此，可以利用量子比特光谱学来研究这些物理特性，特别是TLS本身具有量子相干性的程度。研究人员发现，通过这种方式应该能够确定TLS本身的退相干速率和能级间隔。

据悉，两能级系统（TLSs）是众多量子计算平台中自旋量子比特退相干的主要来源。尽管付出了很多努力，但很难显著减轻这种噪声的影响，或者在许多情况下，难以完全理解其物理起源。

附：英文原文

Title: Using stochastic resonance of two-level systems to increase qubit coherence times

Author: Yujun Choi, S. N. Coppersmith, Robert Joynt

Issue&Volume: 2024/11/05

Abstract: Two-level systems (TLSs) are the major source of dephasing of spin qubits in numerous quantum computing platforms. In spite of much effort, it has been difficult to substantially mitigate the effects of this noise or, in many cases, to fully understand its physical origin. We propose a method to make progress on both of these issues. When an oscillating field is applied to a TLS, stochastic resonance can occur and the noise spectrum is moved to higher frequencies. This shift in the TLS noise spectrum will increase the dephasing times of the qubits that they influence. Furthermore, the details of this effect depend on the physical properties of the noise sources. Thus one can use qubit spectroscopy to investigate their physical properties, specifically the extent to which the TLSs themselves possess quantum coherence. We find that it should be possible to determine the dephasing rate and the energy-level separation of the TLS themselves in this way.

DOI: 10.1103/PhysRevA.110.052408

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.052408