A quantum system interacts with its environment—if ever so slightly—no matter how much care is put into isolating it¹. Therefore, quantum bits undergo errors, putting dauntingly difficult constraints on the hardware suitable for quantum computation². New strategies are emerging to circumvent this problem by encoding a quantum bit non-locally across the phase space of a physical system. Because most sources of decoherence result from local fluctuations, the foundational promise is to exponentially suppress errors by increasing a measure of this non-locality^3,4. Prominent examples are topological quantum bits, which delocalize information over real space and where spatial extent measures non-locality. Here, we encode a quantum bit in the field quadrature space of a superconducting resonator endowed with a special mechanism that dissipates photons in pairs^5,6. This process pins down two computational states to separate locations in phase space. By increasing this separation, we measure an exponential decrease of the bit-flip rate while only linearly increasing the phase-flip rate⁷. Because bit-flips are autonomously corrected, only phase-flips remain to be corrected via a one-dimensional quantum error correction code. This exponential scaling demonstrates that resonators with nonlinear dissipation are promising building blocks for quantum computation with drastically reduced hardware overhead⁸.

一个量子系统与它的环境相互作用——如果有的话——无论多么小心地隔离它¹。因此，量子比特会出现错误，对适合量子计算的硬件施加了极其困难的限制²。正在出现新的策略来通过在物理系统的相空间中对量子位进行非局部编码来规避这个问题。由于大多数退相干源是由局部波动引起的，因此基本承诺是通过增加这种非局部性的度量来以指数方式抑制错误^3,4. 突出的例子是拓扑量子比特，它在真实空间上使信息离域，并且空间范围测量非局部性。在这里，我们在超导谐振器的场正交空间中编码一个量子位，该谐振器具有一种特殊机制，可以成对消散光子^5,6。这个过程将两个计算状态锁定到相空间中的不同位置。通过增加这种分离，我们测量了位翻转率的指数下降，同时仅线性增加相位翻转率⁷. 因为位翻转是自动校正的，所以只有相位翻转需要通过一维量子纠错码进行校正。这种指数缩放表明，具有非线性耗散的谐振器是用于量子计算的有前途的构建块，可大大降低硬件开销⁸。