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 overheads¹. 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^2,3,4,5,6,7. However, this strategy relies on one condition: any quantum manipulations of the qubit must not break the protection that has been so carefully engineered^5,8. 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 10 s. 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 490 ns. 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.

由于与环境的不受控制的相互作用，量子位（qubit）很容易出现多种类型的错误。纠正这些错误的常见策略基于量子位架构，涉及巨大的硬件开销¹。一种可能的解决方案是构建本质上可以防止某些类型错误的量子位，因此纠正剩余错误所需的开销大大减少^2,3,4,5,6,7。然而，这一策略依赖于一个条件：对量子位的任何量子操作都不得破坏精心设计的保护^5,8。一种被称为“猫量子位”的量子位被编码在量子动力学系统的多种亚稳态中，从而获得针对位翻转的连续且自主的保护。在此，在超导电路实验中，我们实现了位翻转时间超过 10 秒的猫量子位。与之前发布的猫量子位实现相比，这提高了四个数量级。我们准备并成像了量子叠加态，并测量了大于 490 ns 的相位翻转时间。最重要的是，我们在不破坏位翻转保护的情况下控制了这些量子叠加的相位。该实验以前所未有的水平展示了量子控制和固有位翻转保护的兼容性，展示了这些动态量子位对于未来量子技术的可行性。