RIKEN, Center for Emergent Matter Science (CEMS), Wako-shi, Saitama, 351-0198, Japan.
Laboratoire Pierre Aigrain, Ecole Normale Supérieure-PSL Research University, CNRS, Université Pierre et Marie Curie-Sorbonne Universités, Université Paris Diderot-Sorbonne Paris Cité, 24 rue Lhomond, 75231, Paris Cedex 05, France.
Nat Commun. 2018 Nov 29;9(1):5066. doi: 10.1038/s41467-018-07522-1.
Single-spin qubits in semiconductor quantum dots hold promise for universal quantum computation with demonstrations of a high single-qubit gate fidelity above 99.9% and two-qubit gates in conjunction with a long coherence time. However, initialization and readout of a qubit is orders of magnitude slower than control, which is detrimental for implementing measurement-based protocols such as error-correcting codes. In contrast, a singlet-triplet qubit, encoded in a two-spin subspace, has the virtue of fast readout with high fidelity. Here, we present a hybrid system which benefits from the different advantages of these two distinct spin-qubit implementations. A quantum interface between the two codes is realized by electrically tunable inter-qubit exchange coupling. We demonstrate a controlled-phase gate that acts within 5.5 ns, much faster than the measured dephasing time of 211 ns. The presented hybrid architecture will be useful to settle remaining key problems with building scalable spin-based quantum computers.
半导体量子点中的单自旋量子位有望实现通用量子计算，其单量子比特门保真度超过 99.9%，双量子比特门与长相干时间相结合。然而，与控制相比，量子比特的初始化和读出速度要慢几个数量级，这不利于实现基于测量的协议，如纠错码。相比之下，双自旋子空间编码的单重态-三重态量子位具有高保真度的快速读出的优点。在这里，我们提出了一种混合系统，该系统结合了这两种不同自旋量子位实现方式的优点。通过电可调谐的双量子比特交换耦合实现了两种码之间的量子接口。我们演示了一个控制相位门，其作用时间在 5.5ns 以内，远快于测量得到的 211ns 退相干时间。所提出的混合架构对于解决构建可扩展自旋量子计算机的剩余关键问题将非常有用。
