Universal holonomic quantum gates over geometric spin qubits with polarised microwaves

• Published in: Nature communications 2018-08, Vol.9 (1), p.3227-10, Article 3227
• Main Authors: Nagata, Kodai, Kuramitani, Kouyou, Sekiguchi, Yuhei, Kosaka, Hideo
• Format: Article
• Language: English
• Subjects: 639/624/400/482; 639/766/483/2802; 639/925/927/481; Communication networks; Computers; Diamonds; Elastic scattering; Electron spin; Fault tolerance; Gates; Gating; Humanities and Social Sciences; Magnetic fields; Microwaves; multidisciplinary; Nitrogen; Quantum computers; Quantum entanglement; Quantum theory; Qubits (quantum computing); Repeaters; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• 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. Holonomic quantum gates represent a promising route to noise-tolerant quantum operations. Here, the authors use polarised microwaves to implement nonadiabatic holonomic quantum gates at room temperature and zero magnetic field on NV centers, both on single-qubit and between electron and nuclear spins.