White G A L, Hill C D, Pollock F A, Hollenberg L C L, Modi K
School of Physics, University of Melbourne, Parkville, VIC, 3010, Australia.
School of Mathematics and Statistics, University of Melbourne, Parkville, VIC, 3010, Australia.
Nat Commun. 2020 Dec 9;11(1):6301. doi: 10.1038/s41467-020-20113-3.
In the scale-up of quantum computers, the framework underpinning fault-tolerance generally relies on the strong assumption that environmental noise affecting qubit logic is uncorrelated (Markovian). However, as physical devices progress well into the complex multi-qubit regime, attention is turning to understanding the appearance and mitigation of correlated - or non-Markovian - noise, which poses a serious challenge to the progression of quantum technology. This error type has previously remained elusive to characterisation techniques. Here, we develop a framework for characterising non-Markovian dynamics in quantum systems and experimentally test it on multi-qubit superconducting quantum devices. Where noisy processes cannot be accounted for using standard Markovian techniques, our reconstruction predicts the behaviour of the devices with an infidelity of 10. Our results show this characterisation technique leads to superior quantum control and extension of coherence time by effective decoupling from the non-Markovian environment. This framework, validated by our results, is applicable to any controlled quantum device and offers a significant step towards optimal device operation and noise reduction.
在量子计算机的扩展过程中，支撑容错的框架通常强烈依赖于这样一个假设：影响量子比特逻辑的环境噪声是不相关的（马尔可夫的）。然而，随着物理设备顺利进入复杂的多量子比特领域，人们的注意力正转向理解相关噪声（即非马尔可夫噪声）的出现和缓解，这对量子技术的发展构成了严峻挑战。这种错误类型以前一直难以用表征技术来刻画。在这里，我们开发了一个用于表征量子系统中非马尔可夫动力学的框架，并在多量子比特超导量子设备上进行了实验测试。在无法使用标准马尔可夫技术解释噪声过程的情况下，我们的重构以10的保真度预测了设备的行为。我们的结果表明，这种表征技术通过与非马尔可夫环境有效解耦，实现了卓越的量子控制并延长了相干时间。我们的结果验证了这个框架，它适用于任何受控量子设备，并朝着优化设备操作和降低噪声迈出了重要一步。
