Teleportation-based Quantum Media Conversion
from photons to a nuclear spin in diamond
Yuhei Sekiguchi a, Naeko Niikura a, Ryota Kuroiwa a, Joerg Wrachtrup b and Hideo Kosaka a,*a

Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501, JAPANb
Physikalisches Institut, Research Center SCOPE, and MPI for Solid State Research,
University of Stuttgart, Pfaenwaldring 57, 70569 Stuttgart, Germany* Corresponding author: kosaka@ynu.ac.jp

Quantum information is carried on various kinds of quantum media such as photons, electrons, and nucleus
in the basis of polarization or spin states [1, 2]. Photons transfer a quantum state over long distance, while nuclear
spins store a quantum state for long time. Quantum media conversion between them will be required as an interface
for hybrid quantum systems [3]. The only way to achieve faithful quantum media conversion is to use the quantum
teleportation scheme, which utilize a prepared electron-nucleus entanglement and post-selection of photonelectron entanglement [4]. The redundancy is required to distillate less frequent event into only the success eventwith the help of quantum non-demolition measurement, which makes probabilistic process into deterministic.
Without the post-selection mechanism, we have to make not only a perfect optical cavity [5] but also a perfect
optical link to suppress the inevitable photon loss that lowers the conversion fidelity.
We here report the experimental demonstration of quantum media conversion from photons to a nuclear spinby preparing an entangled state between an electron spin and a nuclear spin and successive photon absorption. The
demonstration relies on the measurement of an entangled state between the photon polarization and the electron
spin through the previously demonstrated entangled absorption [3]. The entangled absorption utilizes an electronic
orbital exited state which is entangled with the spin state to select photons whose polarization state corresponds tothe spin state to absorb. Another important mechanism is the quantum non-demolition measurement called thesingle-shot measurement of an electron spin state by spin-dependent photoluminescence measurement, which postselects only the success event without destroying the stored nuclear spin state to make probabilistic conversion
into deterministic without any optical cavity.
Figure 1 shows the conditional probability of the transferred state from a photon polarization state to a nuclear
spin state. The bright state indicates the photon polarization state that is converted into the nuclear spin state to bemeasured. The fidelity of the conversion is over 90%, which enough exceeds the classical limit of 50%. Although
we used a photon ensemble that consists of around 100 to 1000 photons for the input to speed up the measurement,
the averaged photon number to be absorbed is around one and the scheme is independent of photon number evenwell below one since the distillation mechanism is built in the scheme.
We thank Sen Yang, Helmut Fedder, Ali Momenzadeh Seyed, Norikazu Mizuochi for their discussions andexperimental supports. This work was supported by the NICT Quantum Repeater Project, by the FIRST Quantum
Information Project, and by a Grant-in-Aid for Scientific Research (A)-JSPS (No. 24244044).
References[1] H. Kosaka et al., Phys. Rev. Lett. 100, 096602 (2008).
[2] H. Kosaka et al., Nature 457, 702–705 (2009).
[3] H. Kosaka and N. Niikura, Phys. Rev. Lett. 114, 053603(2015).
[4] D. Bouwmeester et al., Nature 390, 575-579 (1997).
[5] H. P. Spechit et al., Nature 473, 190–193 (2011).

Fig. 1: Conditional probability of transferredstates from a photon polarization state to anuclear spin state. Red squares (blue circles)
show the probability of nuclear spin bright stateof |1⟩ + |−1⟩ (dark state of |1⟩ − |−1⟩).