Institute for Experimental Physics, University of Innsbruck, Innsbruck, Austria.
Institute for Theoretical Physics, University of Innsbruck, Innsbruck, Austria.
Nature. 2021 Jan;589(7841):220-224. doi: 10.1038/s41586-020-03079-6. Epub 2021 Jan 13.
The development of quantum computing architectures from early designs and current noisy devices to fully fledged quantum computers hinges on achieving fault tolerance using quantum error correction. However, these correction capabilities come with an overhead for performing the necessary fault-tolerant logical operations on logical qubits (qubits that are encoded in ensembles of physical qubits and protected by error-correction codes). One of the most resource-efficient ways to implement logical operations is lattice surgery, where groups of physical qubits, arranged on lattices, can be merged and split to realize entangling gates and teleport logical information. Here we report the experimental realization of lattice surgery between two qubits protected via a topological error-correction code in a ten-qubit ion-trap quantum information processor. In this system, we can carry out the necessary quantum non-demolition measurements through a series of local and entangling gates, as well as measurements on auxiliary qubits. In particular, we demonstrate entanglement between two logical qubits and we implement logical state teleportation between them. The demonstration of these operations-fundamental building blocks for quantum computation-through lattice surgery represents a step towards the efficient realization of fault-tolerant quantum computation.
量子计算架构的发展从早期设计和当前嘈杂的设备到成熟的量子计算机，都依赖于使用量子纠错来实现容错。然而，这些纠错能力会增加执行必要的容错逻辑操作的开销，这些逻辑操作是在逻辑量子位上进行的（逻辑量子位是通过纠错码编码在物理量子位的集合中并受到保护的）。实现逻辑操作的最具资源效率的方法之一是晶格手术，其中排列在晶格上的一组物理量子位可以合并和分裂，以实现纠缠门和传送逻辑信息。在这里，我们报告了在一个由拓扑纠错码保护的十个离子阱量子信息处理器中的两个量子位之间的晶格手术的实验实现。在这个系统中，我们可以通过一系列的局部和纠缠门以及辅助量子位上的测量来进行必要的量子非破坏测量。特别是，我们演示了两个逻辑量子位之间的纠缠，并在它们之间实现了逻辑状态的传送。通过晶格手术实现这些操作（量子计算的基本构建块）代表着朝着高效实现容错量子计算迈出的一步。
