# Qubit By Qubit

## An Introduction To Quantum Key Distribution (QKD)

Glance into the world just as though time were gone: and everything crooked will become straight to you-Friedrich Nietzsche

*Quantum physics upended classical physics. It is now upending the race to technological superiority. In a **recent MIT Technology Review **article, Mark Harris-the author wrote about Google enlisting NASA’s help for quantum supremacy. All superpowers today are competing at the edge of the technology frontier. That’s because the next battlefield is a technological one. It is also a bit like Mixed Martial Arts (MMA) because real strength lies at the intersection of many multidisciplinary technologies i.e. quantum physics and cryptography, gene editing and eugenics etc. While this article doesn’t attempt to explain the complete battlefield, it tries to simplify and break down one of the key technologies reshaping it- Quantum Key Distribution (QKD).*

Quantum computing will upend the internet as we know it. The web, in its initial avatar i.e. Web 1.0 consisted of static pages. Web 2.0, powered by the telecom revolution (4G, LTE), resulted in rich dynamic web pages with multimedia content. Web 3.0 will create an Internet of Everything — a combination of the Internet of Value (where crypto currencies and anything of value can be transmitted in its virtual form, using Augmented Reality, over the Blockchain) and the Internet of Things (with zettabytes of data generated by millions of sensors monitoring our every waking moment). Life, literally, will be on the internet. Data will be as ubiquitous as thin air. Such a future needs a future proof encryption method which many believe to be quantum encryption.

# The Problem With Encryption Today

There are basically two types of encryption ie symmetric and asymmetric.

Symmetric key encryption uses the same “secret” key for both encryption and decryption. For a very simpliatic example, let’s say we want to use numbers to denote alphabets. Now, let’s say Alice wants to send Bob the word “yes” it would be encrypted as “25 5 19". Alice and Bob should know the secret key. So, Bob can decyrpt Alice’s message easily. Of course, symmetric key…