Hacking is Useless in Quantum Cryptography

Quantum mechanical techniques not only allow for the development of faster algorithms but also strong cryptography

There is a wealth of really private information on the Internet. Such content is typically protected from interception and reading thanks to sophisticated encryption mechanisms. High-performance quantum computers, however, could quickly decrypt these keys in the future. Therefore, it is fortunate that quantum mechanical techniques not only allow for the development of new, much faster algorithms but also extremely strong cryptography.

Quantum key distribution (QKD) is secure from attacks on the communication channel but not from attacks or alterations of the devices themselves. Therefore, the gadgets may output a key that the maker had previously saved and could have theoretically sent to a hacker.

There are various methods for exchanging quantum mechanical credentials. Either coupled quantum systems are used, or light signals are conveyed from the transmitter to the receiver. Two rubidium atoms that were quantum mechanically entangled were employed in the current experiment. They were located in two laboratories on the LMU campus, 400 meters apart. A 700-meter fiber optic cable that connects the two places runs underneath Geschwister Scholl Square in front of the main structure.

The researchers initially use a laser pulse to stimulate each atom to produce entanglement. The atoms then return to their ground state on their own, emitting photons as they do so. The rotation of the atom is coupled with the polarization of its released photon as a result of the conservation of angular momentum. Joint measurement of the photons at the reception station, when the two light particles arrive after traveling over the fiber optic cable, reveals an entanglement of the atomic quantum memory.

By contrast, security is only assured with conventional QKD approaches when the quantum devices utilized have been appropriately defined. Tim van Leent, says that users of such protocols "had to rely on the specifications supplied by the QKD providers and believe that the device will not transition into another operational mode during the key distribution."

It was restricted in the current configuration by the loss of around half the photons in the fiber connecting the laboratories. In additional tests, the researchers were successful in reducing the photons' wavelength to a low-loss range appropriate for telecommunications. They were able to extend the quantum network connection's range to 33 kilometers in exchange for a small amount of additional noise in this method.