Quantum Teleportation between Remote Qubit Memories with Only a Single Photon as a Resource

Open Access

Quantum Teleportation between Remote Qubit Memories with Only a Single Photon as a Resource

Stefan Langenfeld, Stephan Welte, Lukas Hartung, Severin Daiss, Philip Thomas, Olivier Morin, Emanuele Distante, and Gerhard Rempe

Phys. Rev. Lett. 126, 130502 – Published 30 March 2021

Abstract

Quantum teleportation enables the deterministic exchange of qubits via lossy channels. While it is commonly believed that unconditional teleportation requires a preshared entangled qubit pair, here we demonstrate a protocol that is in principle unconditional and requires only a single photon as an ex-ante prepared resource. The photon successively interacts, first, with the receiver and then with the sender qubit memory. Its detection, followed by classical communication, heralds a successful teleportation. We teleport six mutually unbiased qubit states with average fidelity $\bar{F} = (88.3 \pm 1.3) %$ at a rate of 6 Hz over 60 m.

Received 22 December 2020
Accepted 4 March 2021

DOI:https://doi.org/10.1103/PhysRevLett.126.130502

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Quantum channels Quantum memories Quantum networks Quantum teleportation

Atoms

Atom & ion cooling Cavity resonators

Atomic, Molecular & OpticalQuantum Information, Science & Technology

Authors & Affiliations

Stefan Langenfeld ^*, Stephan Welte^*,†, Lukas Hartung, Severin Daiss, Philip Thomas, Olivier Morin , Emanuele Distante , and Gerhard Rempe

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany

^*S. L. and S. W. contributed equally to this work.
^†To whom correspondence should be addressed. stephan.welte@mpq.mpg.de

Article Text

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Supplemental Material

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References

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Issue

Vol. 126, Iss. 13 — 2 April 2021

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Images

Figure 1
Teleportation of a qubit from Alice to Bob. (a) Setup: Two cavity QED setups are connected with a 60 m long optical fiber. The respective atomic qubits are controlled using a pair of Raman lasers (gray arrows) and read out using a different laser beam (blue arrows). A photon (red wiggly arrow) impinges onto Bob’s setup, is reflected, and then propagates to Alice’s setup. A fiber circulator (circular arrow) directs the photon onto Alice’s cavity and, after its reflection, to a polarization-resolving detection setup. Feedback (double arrow) acts on Bob’s atomic qubit. (b) Quantum circuit diagram. Single-qubit rotations are labeled with an $R$ . The superscript describes the respective pulse area while the subscript describes the rotation axis $x$ ( $| ↑_{z} ⟩ + | ↓_{z} ⟩$ ) or $y$ ( $| ↑_{z} ⟩ + i | ↓_{z} ⟩$ ). After state preparation of the atoms, the photon performs two controlled-NOT gates. To make the protocol unconditional, the $π / 2$ rotation and measurement of Alice’s qubit (dashed box) could be applied only in case of a successful photon detection event independent of the polarization. At the end of the protocol, a state detection of Alice’s atom and the photon is performed (blue squares). These measurement outcomes determine the two classical feedback signals.
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Figure 2
Teleportation results. (a) Density matrices of the single-qubit states that were teleported from Alice to Bob. (b) Teleportation fidelities of the six teleported states. The orange bars show the experimentally (exp) measured fidelities. The error bars are standard deviations of the mean. In gray, we show the simulated (sim) fidelities. The dashed line represents the classically achievable threshold of $2 / 3$ which can be reached with a measure-prepare strategy [22].
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Figure 3
Scan of mean photon number. Teleportation fidelity as a function of the mean photon number in the employed coherent pulse. The blue line is based on a theoretical model (see Supplemental Material [18]). The dashed line shows the classical teleportation threshold of $2 / 3$ . The error bars represent standard deviations from the mean.
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Figure 4
Scan of the delay. (a) Quantum circuit diagram with the added three delay intervals $τ$ . (b) Teleportation fidelity versus the variable delay. The dashed line represents the classical threshold of $2 / 3$ . The blue line is based on our theoretical model (see Supplemental Material [18]). The upper horizontal axis represents the length equivalent corresponding to $τ \times c / 1.5$ , where $c$ is the speed of light and 1.5 the refractive index of the fiber. In this experiment, the mean photon number was chosen a factor of 2 higher compared to the data shown in Fig. 2.
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