近日，法国巴黎高等师范学院的Z. Leghtas及其研究团队取得一项新进展。经过不懈努力，他们实现比特翻转时间超过10秒的猫量子比特的量子控制。相关研究成果已于2024年5月6日在国际权威学术期刊《自然》上发表。

该研究团队在超导电路实验中取得了突破性进展，成功实现了一个比特翻转时间超过10秒的猫量子比特，这一成就比之前的记录提高了四个数量级。研究人员不仅制备并观测了量子叠加态，还测量了超过490纳秒的相翻转次数。尤为重要的是，他们能够在不破坏比特翻转保护的前提下，精准控制这些量子叠加态的相位。这一实验不仅证明了量子控制与固有比特翻转保护之间的高度兼容性，也充分展现了动力学量子比特在未来量子技术中的可行性。

据悉，量子比特在与环境的不受控制交互中容易引发多种错误。传统的纠错策略通常依赖于复杂的量子比特架构，这带来了高昂的硬件成本。为了降低纠错成本，一个潜在方案是构建具备固有保护的量子比特，以预防特定类型的错误。但这一方案的前提是，任何对量子比特的量子操作都不能破坏其精心设计的保护机制。猫量子比特（Cat Qubit）正是一种这样的量子比特，它被编码在量子动力学系统的亚稳态流形中，从而获得持续且自动的比特翻转保护。

附：英文原文

Title: Quantum control of a cat qubit with bit-flip times exceeding ten seconds

Author: Reglade, U., Bocquet, A., Gautier, R., Cohen, J., Marquet, A., Albertinale, E., Pankratova, N., Hallen, M., Rautschke, F., Sellem, L.-A., Rouchon, P., Sarlette, A., Mirrahimi, M., Campagne-Ibarcq, P., Lescanne, R., Jezouin, S., Leghtas, Z.

Issue&Volume: 2024-05-06

Abstract: Quantum bits (qubits) are prone to several types of error as the result of uncontrolled interactions with their environment. Common strategies to correct these errors are based on architectures of qubits involving daunting hardware overheads. One possible solution is to build qubits that are inherently protected against certain types of error, so the overhead required to correct the remaining errors is greatly reduced. However, this strategy relies on one condition: any quantum manipulations of the qubit must not break the protection that has been so carefully engineered. A type of qubit known as a cat qubit is encoded in the manifold of metastable states of a quantum dynamical system, and thereby acquires continuous and autonomous protection against bit-flips. Here, in a superconducting-circuit experiment, we implemented a cat qubit with bit-flip times exceeding 10s. This is an improvement of four orders of magnitude over previously published cat-qubit implementations. We prepared and imaged quantum superposition states, and measured phase-flip times greater than 490ns. Most importantly, we controlled the phase of these quantum superpositions without breaking the bit-flip protection. This experiment demonstrates the compatibility of quantum control and inherent bit-flip protection at an unprecedented level, showing the viability of these dynamical qubits for future quantum technologies.

DOI: 10.1038/s41586-024-07294-3

Source: https://www.nature.com/articles/s41586-024-07294-3