Template for Abstract Submission, HQS2017

1. Corresponding author
Name: Yuhei Sekiguchi
Affiliation: Yokohama National University
Address: 79-5 Tokiwadai, Hodogayaku, Yokohama 240-8501, Japane-mail address: sekiguchi-yuhei-jc@ynu.jp
2. Title, authors, and affiliations
1) Title of the presentation: Optical holonomic quantum gates over an NV spin in diamond
2) Authors’ list: Yuhei Sekiguchi, Naeko Niikura, Ryota Kuroiwa, Hiroki Kano and Hideo Kosaka
3) Authors’ affiliations: Yokohama National University
3. Presentation type (please, check where it applies)□ invited■ contributed (oral presentation preferred)□ contributed (poster presentation preferred)
4. Category (choose the most appropriate one)
□ Coherent phenomena in solids■ Quantum information processing□ Charge and spin physics in nanostructures□ Spintronic materials and devices□ Optical properties of nanostructures□ Photonic nanostructures■ NV centers in diamonds□ Phononic nanosturctures□ MEMS/NEMS and novel mechanical effects□ Novel materials for hybrid quantum systems□ Nanocarbon and 2D materials□ Topological insulators and superconductors□ Quantum metrology□ Quantum functional devices

Optical holonomic quantum gates over an NV spin in diamond
Yuhei Sekiguchi, Naeko Niikura, Ryota Kuroiwa, Hiroki Kano and Hideo Kosaka
Yokohama National University, Yokohama 240-8501, Japan
kosaka-hideo-yp@ynu.ac.jp
Realization of fast fault-tolerant quantum gates on a single spin is the core requirement for solid-state
quantum-information processing. As polarized light shows geometric interference, spin coherence isalso geometrically controlled with light via the spin-orbit interaction. Here, we show that a holonomic
spin qubit in a degenerate subspace of a spin-1 electronic system under a zero field in a nitrogen vacancy(NV) center in diamond allows implementation of optical non-adiabatic holonomic quantum gates [1].
The holonomic spin qubit under quasi-resonant light exposure undergoes a cyclic evolution in the spinorbit space, and acquires a geometric phase or holonomy that results in rotations about an arbitrary axisby any angle defined by the light polarization and detuning (Fig. 1). This enables universal holonomic
quantum gates with a single operation. We demonstrate a complete set of Pauli quantum gates using thegeometric spin preparation and readout techniques. The new scheme opens a path to holonomic quantum
computers and repeaters. We also talk about our recent work toward holonomic manipulation ofentanglement between an electron spin, nuclear spin and a photon [2-4].

Fig.1 Optical holonomic quantum gates. (left) Degenerate three-level Λ system and conceptual explanation for thegeometric spin rotation. (right) Dependence of X-gate fidelity on detuning and pulse length. White numbers
indicate the number of turns used to perform the X gates. Black numbers indicate spin rotation angles.

We thank Y. Matsuzaki, B. Scharfenberger, K. Nemoto, W. Munro, N. Mizuochi, N. Yokoshi, F. Jelezko
and J. Wrachtrup for discussions and experimental help. This work was supported by the National
Institute of Information and Communications Technology (NICT) Quantum Repeater Project and by theJapan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (16H06326,16H01052, 16K13818) and the Ministry of Education, Culture, Sports, Science and Technology(MEXT) ‘Exploratory Challenge on Post-K computer’ project (Frontiers of Basic Science: Challengingthe Limits).
References[1] Yuhei Sekiguchi, Naeko Niikura, Ryota Kuroiwa, Hiroki Kano and Hideo Kosaka, “Opticalholonomic single quantum gates with a geometric spin under a zero field”, Nature Photonics 11,309 (2017).
[2] Yuhei Sekiguchi, Yusuke Komura, Shota Mishima, Touta Tanaka, Naeko Niikura and Hideo Kosaka,“Geometric spin echo under zero field”, Nature Communications 7, 11668 (2016).
[3] Hideo Kosaka, Naeko Niikura, “Entangled Absorption of a Single Photon with a Single Spin inDiamond”, Physical Review Letters 114, 053603 (2015).
[4] Sen Yang, Hideo Kosaka, Joerg Wrachtrup, et al., “High ﬁdelity transfer and storage of photon statesin a single nuclear spin”, Nature Photonics 10, 507-511(2016).