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npj Quantum Information

Quantum teleportation of a photon via absorption and emission for quantum repeater nodes

Raustin Reyes, Yuhei Sekiguchi, Daisuke Itô, Taichi Fujiwara, Kansei Watanabe, Toshiharu Makino, Hiromitsu Kato, Hideo Kosaka

Published Dec 28, 2025• 0 citations
Publisher

Abstract

Absorption and emission, fundamental interactions between light and matter, enable the regeneration of a quantum state of light via matter through concatenated quantum state transfer based on the principle of quantum teleportation. This transfer is enabled by electron spin-orbit entanglement and electron-nuclear spin entanglement inherent within the material. Here, we demonstrate that a photon quantum state imprinted in polarization is transferred to another photon emitted from a nitrogen vacancy (NV) center. This transfer is heralded by the result of the Bell state measurement between the electron and nitrogen nuclear spins. We show that the minimum number of incident photons needed to achieve transfer is, on average, only 0.1 photons, enabling quantum teleportation over 10 km. This demonstration paves the way for a quantum repeater that is robust against phase and intensity errors, unlike the conventional photon interference scheme, thereby facilitating practical quantum networks.

DOI
10.1038/s41534-025-01169-9

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Absorption and emission, fundamental interactions between light and matter, enable the regeneration of a quantum state of light via matter through concatenated quantum state transfer based on the principle of quantum teleportation. This transfer is enabled by electron spin-orbit entanglement and electron-nuclear spin entanglement inherent within the material. Here, we demonstrate that a photon quantum state imprinted in polarization is transferred to another photon emitted from a nitrogen vacancy (NV) center. This transfer is heralded by the result of the Bell state measurement between the electron and nitrogen nuclear spins. We show that the minimum number of incident photons needed to achieve transfer is, on average, only 0.1 photons, enabling quantum teleportation over 10 km. This demonstration paves the way for a quantum repeater that is robust against phase and intensity errors, unlike the conventional photon interference scheme, thereby facilitating practical quantum networks.
Quantum repeaters are essential for overcoming the exponential photon loss that limits entanglement generation over long distances in quantum networks. An absorption-emission-based quantum repeater exploits the fundamental light-matter interactions of a diamond nitrogen-vacancy (NV) center---photon absorption and photon emission---to transfer a quantum state from an absorbed photon to an emitted photon, offering a scalable architecture that operates without photon interference between remote nodes. Here we demonstrate an absorption-emission-based quantum repeater node using a single NV center, realizing the complete single-node operation in which heralded photon-to-memory quantum state transfer, repeat-until-success (RUS) emission of a spin-entangled photon, and quantum teleportation of the memory state onto the emitted photon constitute the essential repeater operation. By characterizing the complete repeater operation as a quantum channel from the absorbed photon to the emitted photon via quantum process tomography, we obtain a process fidelity of 78%. This demonstration establishes the absorption-emission approach as a fundamental building block for scalable quantum repeater architectures and paves the way toward practical long-distance quantum networks.
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.
Abstract Quantum teleportation is a key principle for quantum information technology. It permits the transfer of quantum information into an otherwise inaccessible space, while also permitting the transfer of photon information into a quantum memory without revealing or destroying the stored quantum information. Here, we show reliable quantum state transfer of photon polarization into a carbon isotope nuclear spin coupled to a nitrogen-vacancy center in diamond based on photon-electron Bell state measurement by photon absorption. The carbon spin is first entangled with the electron spin, which is then permitted to absorb a photon into a spin-orbit correlated eigenstate. Detection of the electron after relaxation into the spin ground state allows post-selected transfer of arbitrary photon polarization into the carbon memory. The quantum state transfer scheme allows individual addressing of integrated quantum memories to realize scalable quantum repeaters for long-haul quantum communications, and distributed quantum computers for large-scale quantum computation and metrology.
Quantum entanglement, a key resource for quantum information science, is inherent in a solid. It has been recently shown that entanglement between a single optical photon and a single spin qubit in a solid is generated via spontaneous emission. However, entanglement generation by measurement is rather essential for quantum operations. We here show that the physics behind the entangled emission can be time reversed to demonstrate entangled absorption mediated by an inherent spin-orbit entanglement in a single nitrogen vacancy center in diamond. Optical arbitrary spin state preparation and complete spin state tomography reveal the fidelity of the entangled absorption to be 95%. With the entangled emission and absorption of a photon, materials can be spontaneously entangled or swap their quantum state based on the quantum teleportation scheme.
Abstract Quantum repeaters with multiple quantum memories provide high throughput, low latency, and high fidelity quantum state (qubit) transfer over long distances. However, conventional quantum repeater protocols require full connections among the multiple quantum memories in a repeater node, which is technically challenging. Here, we propose a quantum repeater protocol based on backward propagating photon emission and absorption, where the quantum memories are multiplexed in the time-domain to speed up a single transmission channel without requiring full connectivity, thereby drastically facilitating physical implementation. Although the protocol is described with nitrogen-vacancy (NV) centers in diamond, it is applicable to various physical systems and opens up the possibility of high-speed high-fidelity quantum networks for distributed quantum computation and the quantum Internet.
Conversion of a quantum state from a flying qubit to a memory qubit is crucial for distributed quantum computing. However, this requires precise spatiotemporal or frequency/phase alignment. Here, we experimentally demonstrate quantum teleportation-based state transfer from a photon into a spin in a nitrogen-vacancy center in diamond robust against both spectral and temporal errors. The achieved fidelity exceeds 0.94 within a frequency error of 100 MHz and 0.93 within an arrival-time error of 100 ns. This achievement could enable extraordinarily robust entanglement generation between remote quantum memories compared with the conventional photon-interference-based approaches and paves the way for stable quantum networks.