Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan.
Nat Commun. 2018 Aug 13;9(1):3227. doi: 10.1038/s41467-018-05664-w.
A microwave shares a nonintuitive phase called the geometric phase with an interacting electron spin after an elastic scattering. The geometric phase, generally discarded as a global phase, allows universal holonomic gating of an ideal logical qubit, which we call a geometric spin qubit, defined in the degenerate subspace of the triplet spin qutrit. We here experimentally demonstrate nonadiabatic and non-abelian holonomic quantum gates over the geometric spin qubit on an electron or nitrogen nucleus. We manipulate purely the geometric phase with a polarised microwave in a nitrogen-vacancy centre in diamond under a zero-magnetic field at room temperature. We also demonstrate a two-qubit holonomic gate to show universality by manipulating the electron-nucleus entanglement. The universal holonomic gates enable fast and fault-tolerant manipulation for realising quantum repeaters interfacing between universal quantum computers and secure communication networks.
在弹性散射后，微波与相互作用的电子自旋共享一个非直观的相位，称为几何相位。通常作为全局相位丢弃的几何相位允许对理想的全同量子比特进行通用的整体门操作，我们称之为几何自旋量子比特，它在三重态自旋量子比特的简并子空间中定义。我们在这里通过在室温下零磁场下的钻石中的氮空位中心中的极化微波，在电子或氮原子核上实验性地演示了非绝热和非阿贝尔整体量子门。我们仅通过在零磁场下的钻石中的氮空位中心中的极化微波来操纵几何相位。我们还演示了一个两量子比特整体门，通过操纵电子-核纠缠来展示通用性。通用整体门可用于快速容错操作，以实现通用量子计算机和安全通信网络之间的量子中继器接口。
