TLDR: Researchers were able to send and receive entangled photons over a fiber optic cable that was simultaneously carrying a classical (non-quantum) signal typical of high speed telecommunications. They managed to accomplish this without the classical signal significantly interfering with the quantum measurements.

This was all done in a laboratory using a combination of standard telecommunications equipment for the classical signal and specialized equipment for the quantum signal. It was NOT done on a fiber carrying real internet traffic as the article would suggest.

[–] Whirling_Ashandarei@lemmy.world 35 points 1 week ago (2 children)

Correct, but still amazing because it means quantum internet is achievable over existing infrastructure. Not needing to lay down all new lines around the world for quantum transmissions will mean it gets adopted much faster. Even if specialized equipment is needed on either end of the cable, the hope/assumption would be that specialized equipment on either end will become cheaper as tech advances and scales upward - still a long ways off but cut down significantly.

[–] Markuso213@lemmy.ml 3 points 5 days ago

There are still massive hurdles for using optical fibre networks for quantum information transmission. The biggest lies in attenuation, where information is lost as the optical signal traverses the fibre. This is an exponential decay, so the signal is lost very quickly for longer distances. This is also the case for normal fibre communication, but these signals can be amplified using conventional amplifiers (aka repeaters in some fields), which are conveniently placed every 80 km or so in order to boost the signal. In contrast, quantum states can not be amplified in a similar manner and have to rely on quantum repeaters which, well, are more of a theoretical concept at this point in time.

So, while the specialized equipment you refer to is indeed needed at both ends, the real challenge still lies in the quantum repeaters. Fortunately, satellite based communication is not as heavily punished by attenuation and would require fewer repeating steps (as compared to fibres) to transmit a quantum state from one end of the globe to the other. A handful of few repetition steps is a lot less daunting then the several hundreds that would be required for globe-scale quantum transmissions via fibre.

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