Thanks Gym! ------- Original Message ------- On Friday, July 29th, 2022 at 11:59 PM, jim bell <jdb10...@yahoo.com> wrote:
> Phys.org: Quantum cryptography: Making hacking futile. > https://phys.org/news/2022-07-quantum-cryptography-hacking-futile.html > > The Internet is teeming with highly sensitive information. Sophisticated > encryption techniques generally ensure that such content cannot be > intercepted and read. But in the future high-performance quantum computers > could crack these keys in a matter of seconds. It is just as well, then, that > quantum mechanical techniques not only enable new, much faster algorithms, > but also exceedingly effective cryptography. > > Quantum [key distribution](https://phys.org/tags/key+distribution/) (QKD)—as > the jargon has it—is secure against attacks on the [communication > channel](https://phys.org/tags/communication+channel/), but not against > attacks on or manipulations of the devices themselves. The devices could > therefore output a key which the manufacturer had previously saved and might > conceivably have forwarded to a hacker. With device- independent QKD > (abbreviated to DIQKD), it is a different story. Here, the cryptographic > protocol is independent of the device used. Theoretically known since the > 1990s, this method has now been experimentally realized for the first time, > by an international research group led by LMU physicist Harald Weinfurter and > Charles Lim from the National University of Singapore (NUS). > > For exchanging quantum mechanical keys, there are different approaches > available. Either [light signals](https://phys.org/tags/light+signals/) are > sent by the transmitter to the receiver, or entangled [quantum > systems](https://phys.org/tags/quantum+systems/) are used. In the present > experiment, the physicists used two quantum mechanically entangled [rubidium > atoms](https://phys.org/tags/rubidium+atoms/), situated in two laboratories > located 400 meters from each other on the LMU campus. The two locations are > connected via a [fiber optic cable](https://phys.org/tags/fiber+optic+cable/) > 700 meters in length, which runs beneath Geschwister Scholl Square in front > of the main building. > > To create an entanglement, first the scientists excite each of the atoms with > a laser pulse. After this, the atoms spontaneously fall back into their > [ground state](https://phys.org/tags/ground+state/), each thereby emitting a > photon. Due to the conservation of angular momentum, the spin of the atom is > entangled with the polarization of its emitted photon. The two [light > particles](https://phys.org/tags/light+particles/) travel along the fiber > [optic cable](https://phys.org/tags/optic+cable/) to a receiver station, > where a joint measurement of the photons indicates an entanglement of the > atomic quantum memories.
