近日，瑞士IBM量子公司的Daniel J. Egger及其研究团队取得一项新进展。经过不懈努力，他们成功结合量子处理器与实时经典通信。相关研究成果已于2024年11月20日在国际权威学术期刊《自然》上发表。

该研究团队通过实验实现了错误缓解的动态电路和电路切割技术，利用两个各有127个量子比特、通过经典链路实时连接的量子处理单元（QPU），在总共142个量子比特上创建了需要周期性连接的量子态。在动态电路中，量子门可以在运行时（即量子比特相干时间的一小部分内）由电路中途测量的结果经典地控制。

实时经典链路使研究人员能够在一个QPU上，根据另一个QPU上的测量结果有条件地应用量子门。此外，错误缓解的控制流增强了量子比特的连接性和硬件的指令集，从而提高了该量子计算机的通用性。这项研究工作表明，借助由实时经典链路实现的错误缓解动态电路，研究人员可以将多个量子处理器当作一个来使用。

据悉，量子计算机依据量子力学的规律处理信息。当前的量子硬件存在噪声问题，信息存储时间短暂，且仅限于少量的量子位，即量子比特，这些量子比特通常以平面连接的方式排列。然而，许多量子计算应用需要的连接性，超出了单个量子处理单元（QPU）所能提供的平面晶格结构，同时也需要比单个QPU所能提供的更多的量子比特。业界希望通过使用经典通信来连接多个QPU，以克服这些限制，但这一方法尚未得到实验验证。

附：英文原文

Title: Combining quantum processors with real-time classical communication

Author: Carrera Vazquez, Almudena, Tornow, Caroline, Rist, Diego, Woerner, Stefan, Takita, Maika, Egger, Daniel J.

Issue&Volume: 2024-11-20

Abstract: 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 connectivity. 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.

DOI: 10.1038/s41586-024-08178-2

Source: https://www.nature.com/articles/s41586-024-08178-2