Entanglement transfer from microwaves to diamond NV centers

Hiroki Kano, Yuhei Sekiguchi, Ryota Kuroiwa +5 more

Ignas Lekavicius, D. Andrew Golter, Thein Oo +1 more

Angela Gomez, Ferney J. Rodríguez, Luis Quiroga

Nitrogen-vacancy (NV) defect centers in diamond are strong candidates to generate entangled states in solid-state environments even at room temperature. Quantum correlations in spatially separated NV systems, for distances between NVs ranging from a few nanometers to a few kilometers, have been recently reported. In the present paper, we consider the entanglement transfer from two-mode microwave-squeezed (entangled) photons, which are in resonance with the two lowest NV electron spin states, to initially unentangled NV centers. We first demonstrate that the entanglement transfer process from quantum microwaves to isolated NV electron spins is feasible. We then proceed to extend the previous results to more realistic scenarios where $^{13}\mathrm{C}$ nuclear spin baths surrounding each NV are included, quantifying the entanglement transfer efficiency and robustness under the effects of dephasing/dissipation noisy nuclear baths. Finally, we address the issue of assessing the possibility of entanglement transfer from the squeezed microwave light to two remote nuclear spins closely linked to different NV centers.

许丽 Xu Li, 刘阿鹏 LIU A-peng

Yong Zhang, Zhong Ding

As a kind of hybrid spin system, nitrogen-vacancy (NV) centers in diamond have shown great advantages in implementing quantum registers for quantum information processing (QIP). When scaling up quantum registers to quantum networks for long-distance quantum communication and distributed quantum computation, determining how to entangle two registers in distant nodes is a basic challenge in the absence of direct interactions. In this paper, we present a scheme for entangling two distant NV centers based on the special optical absorption and emission of NV centers. In this demonstration, we transfer the entanglement information of a pair of photons to nuclear spins in NV centers and create remote NV–NV entanglement mediated by entangled photons. We then explain how to extract the entangled information from NV centers to prepare on-demand entangled photons for optical quantum information processing. The strategy of entanglement transfer between spins and photons demonstrated herein may pave the way for an NV-center-based quantum network.

M. Haruyama, S. Fujii, Abe Hiroshi +6 more

Nitrogen-Vacancy (NV) centers in diamond are expected as highly sensitive magnetic sensors operable at room temperature. One major challenge in improving sensitivity is controlling the NV axis orientation. In diamond crystals, NV centers are typically randomly oriented along four crystallographic axes. Since only NV centers on a specific axis are utilized, NV centers on other axes act as fluorescence noise. Therefore, selectively forming NV centers along a single crystallographic axis is expected to enhance sensitivity. Perfectly oriented NV centers can be fabricated by nitrogen doping during chemical vapor deposition (CVD) growth, however, achieving a high NV center density remains challenging. In contrast, a high NV center density can be achieved by electron-beam irradiation followed by post-annealing, although orientation control remains difficult. In this study, we attempted to control NV center orientation by applying microwave annealing after electron-beam irradiation. Generally, microwave irradiation of material induces heating via Joule, dielectric and magnetic losses. Diamond has negligible dielectric and magnetic losses, so a boron doped diamond layer was formed as conductive layer and microwave annealing was performed via Joule loss. Because the conductive layer is thin, an electric field is applied throughout the whole diamond, resulting in a drift current flowing across the diamond. We thought that by controlling this current in the [111] direction, it would be possible to preferentially form [111]-oriented NV centers.