Quantum teleportation over 143 kilometres using active feed-forward

Abstract

The quantum internet is predicted to be the next-generation information processing platform, promising secure communication and an exponential speed-up in distributed computation. The distribution of single qubits over large distances via quantum teleportation is a key ingredient for realizing such a global platform. By using quantum teleportation, unknown quantum states can be transferred over arbitrary distances to a party whose location is unknown. Since the first experimental demonstrations of quantum teleportation of independent external qubits, an internal qubit and squeezed states, researchers have progressively extended the communication distance. Usually this occurs without active feed-forward of the classical Bell-state measurement result, which is an essential ingredient in future applications such as communication between quantum computers. The benchmark for a global quantum internet is quantum teleportation of independent qubits over a free-space link whose attenuation corresponds to the path between a satellite and a ground station. Here we report such an experiment, using active feed-forward in real time. The experiment uses two free-space optical links, quantum and classical, over 143 kilometres between the two Canary Islands of La Palma and Tenerife. To achieve this, we combine advanced techniques involving a frequency-uncorrelated polarization-entangled photon pair source, ultra-low-noise single-photon detectors and entanglement-assisted clock synchronization. The average teleported state fidelity is well beyond the classical limit of two-thirds. Furthermore, we confirm the quality of the quantum teleportation procedure without feed-forward by complete quantum process tomography. Our experiment verifies the maturity and applicability of such technologies in real-world scenarios, in particular for future satellite-based quantum teleportation.

Physics: Unite to build a quantum Internet

“…Certain technologies will be better than others for particular tasks, and each has its limitations. Polarized photons have been used to transfer quantum information over more than 100 kilometres 3 , but only probabilistically. Superconducting devices can send information without losses through a chip, but only for a split second, after which the information is scrambled by interactions with the environment.…”

“…Polarization qubits perform best in terms of distance -holding a record of 143 kilometres 3 . But currently, only 50% of these qubits can be teleported 2 .…”

Quantum computing on encrypted data

“…2c. The auxiliary qubit is randomly prepared by the client in one of the four rotated BB84 states, P y Z d þ i j , using waveplates and Pockels' cells as fast optical switches [24][25][26] (see Methods), and then sent to the server. The Pockels' cells are switched at 1 MHz-two orders of magnitude faster than the single-photon detection rate from spontaneous parametric downconversion.…”

Bell’s Universe: A Personal Recollection

“…Fascinating experiments on quantum teleportation [164,165] and quantum cryptography [166,167] followed. Then a race started in achieving records of entanglement based long distance quantum communication.…”