Quantumcomputing For The Very Curious

“This essay explains how quantum computers work. It’s not a survey essay, or a popularization based on hand-wavy analogies. We’re going to dig down deep so you understand the details of quantum computing. Along the way, we’ll also learn the basic principles of quantum mechanics, since those are required to understand quantum computation.

Learning this material is challenging. Quantum computing and quantum mechanics are famously ‘hard’ subjects, often presented as mysterious and forbidding. If this were a conventional essay, chances are that you’d rapidly forget the material. But the essay is also an experiment in the essay form. As I’ll explain in detail below the essay incorporates new user interface ideas to help you remember what you read. That may sound surprising, but uses a well-validated idea from cognitive science known as spaced-repetition testing. More detail on how it works below. The upshot is that anyone who is curious and determined can understand quantum computing deeply and for the long term.”

Andy Matuschak and Michael Nielsen. “Quantumcomputing For The Very Curious.” Quantam.country. March 18, 2019.

Looks like I’m going to have to brush up on my math.

China’s Quantum Communication Network

“The crucial advantage of this so-called quantum key distribution is that if anyone tries to intercept the light particles, they necessarily alter or destroy them.

What this means is that any attempt at hacking will immediately be noticed by the original sender and the intended receiver – hence its description as ‘unhackable’.”

A practical application of research into “teleportation” and quantum networks.

First Object Teleported from Earth to Orbit

“Back in the 1990s, scientists realized they could use this link to transmit quantum information from one point in the universe to another. The idea is to ‘download’ all the information associated with one photon in one place and transmit it over an entangled link to another photon in another place.

This second photon then takes on the identity of the first. To all intents and purposes, it becomes the first photon. That’s the nature of teleportation and it has been performed many times in labs on Earth…In theory, there should be no maximum distance over which this can be done…

‘We report the first quantum teleportation of independent single-photon qubits from a ground observatory to a low Earth orbit satellite—through an up-link channel— with a distance up to 1400 km,’ says the Chinese team…

‘This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet,’ says the team.”
First Object Teleported From Earth to Orbit.” MIT Technology Review. July 10, 2017