Quantum computers process information with the laws of quantum mechanics. Current quantum hardware is noisy, can only store information for a short time and is limited to a few quantum bits, that is, qubits, typically arranged in a planar connectivity¹. However, many applications of quantum computing require more connectivity than the planar lattice offered by the hardware on more qubits than is available on a single quantum processing unit (QPU). The community hopes to tackle these limitations by connecting QPUs using classical communication, which has not yet been proven experimentally. Here we experimentally realize error-mitigated dynamic circuits and circuit cutting to create quantum states requiring periodic connectivity using up to 142 qubits spanning two QPUs with 127 qubits each connected in real time with a classical link. In a dynamic circuit, quantum gates can be classically controlled by the outcomes of mid-circuit measurements within run-time, that is, within a fraction of the coherence time of the qubits. Our real-time classical link enables us to apply a quantum gate on one QPU conditioned on the outcome of a measurement on another QPU. Furthermore, the error-mitigated control flow enhances qubit connectivity and the instruction set of the hardware thus increasing the versatility of our quantum computers. Our work demonstrates that we can use several quantum processors as one with error-mitigated dynamic circuits enabled by a real-time classical link.

量子计算机根据量子力学定律处理信息。当前的量子硬件是嘈杂的，只能在短时间内存储信息，并且仅限于几个量子比特，即量子比特，通常以平面连接¹ 排列。但是，量子计算的许多应用程序需要比硬件提供的平面晶格更多的连接，其量子比特数超过单个量子处理单元 （QPU） 上可用的量子比特。社区希望通过使用经典通信连接 QPU 来解决这些限制，这尚未得到实验验证。在这里，我们实验性地实现了误差缓解的动态电路和电路切割，以创建需要周期连接的量子态，使用多达 142 个量子比特跨越两个 QPU，每个量子比特有 127 个量子比特通过经典链路实时连接。在动态电路中，量子门可以由运行时（即量子比特相干时间的一小部分）内的中间电路测量结果经典控制。我们的实时经典链接使我们能够在一个 QPU 上应用量子门，具体取决于另一个 QPU 上的测量结果。此外，误差缓解控制流增强了量子比特连接和硬件的指令集，从而提高了量子计算机的多功能性。我们的工作表明，我们可以将多个量子处理器作为一个量子处理器使用，并通过实时经典链路启用误差缓解动态电路。