Template for Abstract Submission, HQS2017

1. Corresponding author
Name: Hideo Kosaka
Affiliation: Yokohama National University
Address: 79-5 Tokiwadai, Hodogayaku, Yokohama 240-8501, Japane-mail address: kosaka-hideo-yp@ynu.ac.jp
2. Title, authors, and affiliation
1) Title of the presentation: Deterministic measurement of a nuclear spin in diamond under azero field
2) Authors’ list:
Riyo Enyo1, Takaaki Nakamura1, Taiichi Ishizaka1, Yuhei Sekiguchi1 and Hideo Kosaka1*

3) Authors’ affiliations:
1Yokohama 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

Deterministic measurement of a nuclear spin in diamond under a zero field
Riyo Enyo1, Takaaki Nakamura1, Taiichi Ishizaka1, Yuhei Sekiguchi1 and Hideo Kosaka1*1
Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan
kosaka-hideo-yp@ynu.ac.jp
Quantum repeaters, which enables long-distance quantum communications, require complete Bellmeasurement with extremely high fidelity for the entanglement swapping or the quantum teleportation[1]. However, it is impossible to measure a quantum state deterministically by itself. We thus devised atechnique of the QND-like read out, which allows to measure the quantum state repeatedly.
We demonstrate the deterministic measurement of the quantum state of a nuclear spin in a nitrogenvacancy (NV) center in diamond under a zero field [2,3]. We were able to measure the nuclear spin of
the target 14N impurity atom by repeatedly measuring the spin state of the entangled ancillary electron(Fig. 1). After preparing the nuclear spin into the mI=0 state, we observed 5.2 photons on average over
96-time repeated optical readouts of the electron spin in the mS=0 state. It showed clear separation in
the count distribution depending on the mI state (bars in Fig.2), indicating that we can perform thedeterministic measurement to distinguish the nuclear spin state whether mI=0 or ±1 with a fidelity of
93% in average (line in Fig.2) even under a zero field, which is ideal for our quantum repeater scheme.

Fig.1 Quantum circuit for the conventional (upper) Fig.2 The distribution of the photon counts and thecorresponding fidelity to distinguish the nuclear spin state.
and the deterministic (lower) measurements.

We thank Yuichiro Matsuzaki, Kae Nemoto, William Munro, Norikazu Mizuochi, Fedor Jelezko, andJoerg Wrachtrup for their discussions and experimental help. This work was supported by National
Institute of Information and Communications Technology (NICT) Quantum Repeater Project, and by
Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (24244044,16H06326, 16H01052) and Ministry of Education, Culture, Sports, Science and Technology (MEXT)
as “Exploratory Challenge on Post-K computer” (Frontiers of Basic Science: Challenging the Limits).
References[1] 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).
[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] 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).