Imagine a world where you have a lock and a set of keys. In fact you have a lot of keys, say 1,000,000,000. You are asked to open the lock as quickly as possible. You pick a key at random, insert into the lock, turn the key and the lock opens. You would seen as a very lucky person. Now imagine the lock isn’t a physical but digital like a password for a website. This time you are not trying to open the lock but you are building the lock and key combination. You could make the lock super complicated or you could add ‘must be lucky’ to open – only a lucky person can open it like you.

Quantum computing is based on quantum mechanics and quantum mechanics is like magic and science fiction added together and then made a thousand times more crazy. The reason for the difficulty in understanding quantum mechanics is many of the explanations of how things should be can not be proved due to the current limitation of our technology and the limit of what we can experience through our senses.

So how does one explain quantum computing if quantum mechanics is so difficult to comprehend? Does one have to be physics professor or a mathematics genius before even starting to look at quantum computing? Absolutely not. However, you do need to let your mind go a little, either trust or understand the models put forward, and learn a little every day. If I had to explain how to ride a bike you’d never get on. I think quantum computing is similar but you don’t hurt when you fall off.

First – What is a computer? The very basics

Before getting into the complexities or quantum computing we need to have a basic understanding of computing to put the quantum bit on top off. Computation is the action of mathematical calculation normally by following a set of steps. For example you can compute your bill in a restaurant to calculate the total charge that includes a 10% tip. This is an example of a linear calculation (cost of food and drink x service charge = total cost of meal). Computation can branch when a certain conditions is meet. In the restaurant example if the cost of food and drink is above 100 then the service charge changes to 15%. The computation is then: if the cost of food and drink is less than 100 then multiple by 0.1 otherwise multiply by 0.15. Following these computational rules is brilliant for machines as they can do calculations never fast especially if the numbers are limited to either 0 or 1. This is called binary and for todays computers this the language they talk. For example the number 0 = 0, 1 = 1, 2 = 10, 3 = 11. Here’s a coolish game to learn binary if interested – binary game.

There is a problem with computation that you may have picked up in the example above. This is where humans can be a pain. The instruction says “a service charge of 15% will be applied to food and drink over £100. The reason for this English is a bill is rarely going to exactly 100. However from a computation point of view we have to be explicit. It should say “a service charge of 15% will be applied to a food and drink equal to or over £100. For these calculation you don’t need a computer machine you just need a computer and that can be the waiting staff. However, an electronic machine is normally much faster and can print receipts. Computers do computation based on the data coming in and the instructions given to produce a result or an output.

Computers do all their calculations in a processing unit. All computers have at least one called the central processing unit or CPU but it can have many such as for handling graphics where there will be a Graphical Processing Unit or GPU. Along with the CPU doing the calculation or, more precisely the arithmetic and instructions, there is storage for putting the input values and the output results. As the CPU has to do lots of calculations the data coming into the CPU is often temporary. Due to this nature it’s called memory in the same way you have memory to recall and calculate things (as your brain is like a computer-ish). With a CPU and memory that holds information in binary form the last thing you need are those instructions to follow (multiplying the cost of food and drink by the service charge). These instructions are called algorithms (named after a 9th-century Persian mathematician around 800 CE) or programs which tend to have multiple algorithms inside them. That’s pretty much it. All computers today have the same components as a person with an abacus, pen and paper, or fancy laptop: input, storage, arithmetic, instructions, output.

Second: What is Quantum Mechanic? The power of a quantum computer

For this part you need to have an understanding of quantum mechanics which I think would be fair to say is complicated. So, I’ll try and explain this at level that is easy to understand but doesn’t take a lot of time.

Quantum mechanics explains how things might work at the very, very small size (it’s so mind bending that there isn’t agreement). When I say small I mean things that have little to no mass like light or a tiny amount of mass like an electron the negatively charged particle involved in electricity. If you stop reading here just take away that quantum mechanics is how very, very small things interact.

Light packets

Let’s start with light as everyone knows what it is and it keeps things a little simpler to begin. As you know light is really cool stuff. It can travel through a vacuum, through glass, bounce off mirrors before being absorb into something. Before the start of the 19th century (1800) light for most people was the thing we could see and feel generated by the Sun in the sky and fires on Earth. Light, fire and heat was a fundamental skill that humans had mastered.

At the start of the 19th century (1800 onwards) this started to change as people started to play with light. The first discovery that light wan’t all that we could see. In 1801 astronomy and all round wiz with glass and lenses William Herschel who looked down instead of up discovered that the far edge red of a beam of white light that has been split by a prism warmed a thermometer more than the green or blue colour. When he looked outside of the visible red light it heated the thermometer even faster before dropping away. Herschel called this ‘light’ below red or infrared. Suddenly light wasn’t just what could be seen; other things were going out what our eyes could see.

Inventor and all round experimenter John Wilhelm Ritter heard about this and dropped his experiments of electricity to see if there was an opposite to this infrared that would have a cooling effect (you might be thinking thermodynamics/heat doesn’t work like that and you would be right but Ritter was a curious fellow). When Ritter focussed the far end of light spectrum – blue, violet on a thermometer there was no change in temperature (no surprise). Switching to materials that do change with light absorption, namely silver halides, Ritter noticed an increase in darkening the further down the light spectrum you went (red: not much, violet: a lot). Like Herschel the year before Ritter went past the visible light and off to the side to find this area changed the material dark quicker than any part of the visible spectrum. Ritter called this ultraviolet (Ritter was never recognised as notable scientist at the time and died at 33 with only his efforts in UV captured much later).

At the same time that non-visible light was discovered (infrared (1800) and ultraviolet (1801)) the science world was being transformed by a new technology – electricity. In 1800 Alessandro Volta in affected invented the electric battery.

The battery allowed for many experiments with electricity as scientist and engineers had a portable and stable store of electricity (it also allowed for break throughs in Chemistry but that is another story). First the discovery that wires carrying an electric current create a magnetic field detected by a compass needle.

This connected electricity and magnetism directly. This connection lead to the recognition and then the formulation of electromagnetism (1819 – 1820: Hans Christian Ørsted (observation) and Andre-Marié Ampère (mathematics) as a single force.

The practical use of electricity and magnets was realised by Michael Faraday who was more an engineer than a pure scientist. Faraday noticed that if you move a magnet through a coil of wire then an electrical current was created. Faraday had created a force on the wire that “

From here electricity could produce magnetism (electromagnets), magnetism could generate electricity (electrical generator) and, both could produce movement (electric motor (Michael Faraday). These three discoveries created the electrical telegraph that created near instant global communication for the first time, the electrical generator that could power factories and light cities and, the electrical motor that could move things with precision without need for a solid fuel or oxygen (very handy).

The work on light at the start of the 19th century and the connection between electricity and magnetism was brought together by James Clerk Maxwell who proved a genius connection between electricity and magnetism and light (1864). The unification of

Light was defined as behaving and travelling like a wave in the same way a wave moves in the seas. Waves have certain properties: Wavelength – the distance from one part of a wave to the next corresponding part like the top of one to the top of another. Warning – mathematics. Wavelength is measured as a length like metres or milimeters e.g. 2m or 2mm. Frequency is the number of waves that pass a given point in a given time. Frequency is measured in distance waves/time e.g. 2m wave / 2 seconds = frequency = 1/s or 1^s-1.

which proposed a where was a spectrum of electrical and magnetic effects that depended on the wavelength of the light or radiation they had. Ti Heinrich Hertz

The 19th was an amazing time in science due to the very rapid advances in all areas due to one particular application – electricity. To cut a never long century short, and to skip over a key pllayer

Chemistry and and rebefore going back to his electricity and

does’focus owas by with experiments showing that when white light was split with a prism and the region just past the edge of the visible red side heated up a thermometer more than the green, blue, or the violet edge of the light (called infra-red or ‘below red’ by famous astronomy and wiz with glass ). The other edge of visible light was discovered a year later (1801) by who was looking for the opposite cooling effect (which makes scientific sense as many things in nature have opposites and blue is seen as the colour of cold as it’s opposite red). Ritter didn’t find a cooling effect but a strange property that light towards the violet end turn light sensitive particles, called silver halides, darker quicker than red end. When he looked past the visible colour the area turned particles black even faster. He called this ultravio when exposed

(actual fires, and candles). At this time light provide illumination and warm where needed. or more precisely, visible light is a form of electromagnetic radiation. Until the Electromagnetic radiation has similar

that is a result of an atom giving off energy of a particular amount that travels out away at the speed of light and through electrical and magnetic fields. These packets of energy are called photons. Electromagnetic radiation = photons travelling at the speed of light* (*there are very specific definitions but this is fine for now).

Assuming you have accepted the idea of photons and packets then the next step is change the language from packets to quantum. Photons have defined quantums of energy.