Detecting photons transporting qubits without destroying quantum information  March 25, 2021
Photons that carry qubits over long distances are easily deflected from their path in the air or absorbed in glass fibers—and suddenly, the quantum information is lost. An international team of researchers (Germany, Spain) has developed a physical protocol that can indicate whether the qubit is lost at intermediate stations of the quantum transmission. If this is the case, the transmitter can send the qubit again with significantly less delay than if the loss is noticed only at the receiving end. The protocol only detects the qubit photon and not measure it. They achieved a nondestructive detection efficiency upon qubit survival of 79 ± 3 per cent and a photon survival probability of 31 ± 1 per cent and preserved the qubit information with a fidelity of 96.2 ± 0.3 per cent. They showed that the detector they used for their experiment would accelerate the transmission of quantum information at a greater distance than 14 kilometers…read more. Open Access TECHNICAL ARTICLE 

Nondestructive photonic qubit detector. Credit: Nature volume 591, pages 570–574(2021)

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