Quantum internet closer as physicists stretch spooky link between atoms

Mario Mastriani

Quantum stretching is a technique to make quasi-copies of an arbitrary qubit without violating the No-Cloning Theorem. These quasi-copies of the original qubit contain all the information of the original but at the cost of duplication in its size each time the technique is applied. Basically, a stretched bit or subit is obtained applying a single, unitary and reversible gate, i.e., we can recover the original qubit from its subit. Quantum stretching will allow us simultaneous teleportation to multiple destinations of the same subit, with the consequent potential that this has for quantum internet in configurations from 1 to N, however, always taking into account the duplication of qubit size to be quasi-copied every time the technique is applied. Finally, quantum stretching is particularly useful to make satellite bifurcations in the quantum internet context.

Sumeet Khatri, Anthony J. Brady, Renée A. Desporte +2 more

Recent experimental breakthroughs in satellite quantum communications have opened up the possibility of creating a global quantum internet using satellite links. This approach appears to be particularly viable in the near term, due to the lower attenuation of optical signals from satellite to ground, and due to the currently short coherence times of quantum memories. These drawbacks prevent ground-based entanglement distribution using atmospheric or optical-fiber links at high rates over long distances. In this work, we propose a global-scale quantum internet consisting of a constellation of orbiting satellites that provides a continuous on-demand entanglement distribution service to ground stations. The satellites can also function as untrusted nodes for the purpose of long-distance quantum-key distribution. We determine the optimal resource cost of such a network for obtaining continuous global coverage. We also analyze the performance of the network in terms of achievable entanglement-distribution rates and compare these rates to those that can be obtained using ground-based quantum-repeater networks.

Eugene Simon Polzik

QUANTUM entanglement is one the weirdest features of quantum mechanics and is at the heart of most of the paradoxes in quantum theory. Erwin Schrödinger considered it to be the most profound characteristics of quantum mechanics and Albert Einstein called it spooky. Entanglement is an attribute that links two or more quantum systems as one and allows particles with two distinct quantum states to have a much closer relationship than classical physics permits. For instance it is possible to create pairs of photons that have their polarizations entangled: if the first photon is circularly polarized in a right-handed sense, then the second photon is always polarized in a left-handed sense, and vice versa.

Stefano Pirandola, Samuel L. Braunstein