Quantum Teleportation Between Photons From Two Distant Light Sources Achieved

Researchers in Germany achieved a major milestone for the future quantum internet by successfully teleporting quantum information between photons generated by two different, physically separated quantum dots — something never accomplished before due to the difficulty of producing indistinguishable photons from remote sources. At the University of Stuttgart, the team succeeded in teleporting the polarization state of a photon originating from one quantum dot to another photon from a second quantum dot. One quantum dot generates a single photon, the other an entangled photon pair. Entangled means that the two particles constitute a single quantum entity, even when they are physically separated. One of the two particles travels to the second quantum dot and interferes with its light particle. The two overlap. Because of this superposition, the information of the single photon is transferred to the distant partner of the pair.

Instrumental for the success of the experiment were quantum frequency converters, which compensate for residual frequency differences between the photons. These converters were developed by a team led by Prof. Christoph Becher, an expert in quantum optics at Saarland University. […] In the Stuttgart experiment, the quantum dots were separated only by an optical fiber of about 10 m length. “But we are working on achieving considerably greater distances,” says Strobel. In earlier work, the team had shown that the entanglement of the quantum dot photons remains intact even after a 36-kilometer transmission through the city center of Stuttgart. Another aim is to increase the current success rate of teleportation, which currently stands at just over 70%. Fluctuations in the quantum dot still lead to slight differences in the photons. The findings have been published in the journal Nature Communications.