Quantum teleportation1 is an important ingredient in distributed quantum networks2, and can also serve as an elementary operation in quantum computers3. Teleportation was first demonstrated as a transfer of a quantum state of light onto another light beam4,5,6; later developments used optical relays7 and demonstrated entanglement swapping for continuous variables8. The teleportation of a quantum state between two single material particles (trapped ions) has now also been achieved9,10. Here we demonstrate teleportation between objects of a different nature—light and matter, which respectively represent ‘flying’ and ‘stationary’ media. A quantum state encoded in a light pulse is teleported onto a macroscopic object (an atomic ensemble containing 1012 caesium atoms). Deterministic teleportation is achieved for sets of coherent states with mean photon number (n) up to a few hundred. The fidelities are 0.58 ± 0.02 for n = 20 and 0.60 ± 0.02 for n = 5—higher than any classical state transfer can possibly achieve11. Besides being of fundamental interest, teleportation using a macroscopic atomic ensemble is relevant for the practical implementation of a quantum repeater2. An important factor for the implementation of quantum networks is the teleportation distance between transmitter and receiver; this is 0.5 metres in the present experiment. As our experiment uses propagating light to achieve the entanglement of light and atoms required for teleportation, the present approach should be scalable to longer distances.
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The experiment was performed at the Niels Bohr Institute, and was funded by the Danish National Research Foundation through the Center for Quantum Optics (QUANTOP), by EU grants COVAQIAL and QAP, and by the Carlsberg Foundation. I.C. and E.S.P. acknowledge the hospitality of the Institut de Ciències Fotòniques (ICFO) in Barcelona where ideas leading to this work were first discussed. The permanent address of K.H. is the Institut für theoretische Physik, Innsbruck, Austria.
This file contains additional details on the following methods used in this study. Atomic state variances, optimization of classical gains and the fidelity calculation. Projection noise measurement and determination of the coupling constant κ. Atomic decoherence.
Calculation of the fidelity for a qubit teleportation and a protocol with improved fidelity.
About this article
International Journal of Theoretical Physics (2018)