*Maybe you could tell me what you think it going on here…*

*And please, speak as you might to a young child – or a golden retriever.*

That’s a line from the film *Margin Call*.

If you haven’t seen it, it chronicles the first 24 hours of the 2007 financial crisis at a fictional investment bank.

The guy speaking is the chairman of the board, played by Jeremy Irons. He’s asking a young analyst to explain what’s happening.

It’s a great film if you like watching lots of fictional high-powered people trying to deal with a problem they can’t overcome or even really understand.

Anyway. The line, I think, is a better version of the popular internet acronym ELI5, which stands for “explain it like I’m five”.

ELI5 is applied to all kinds of hard to understand situations, and today, I’m applying it to the strange world of quantum computing.

I’m going to try explain it as I would to a golden retriever.

Mostly because that’s the level that I understand it at myself. And also because with a subject this complicated it’s easy to get bogged down in bits that are irrelevant to most people.

I’ve read journalists writing analogies to explain quantum computing, and even their analogies end up woefully complicated and convoluted.

I’ll try to avoid that. And I’ll also try to answer the question that always comes up when quantum computing is mentioned: will it break everything?

Okay, let’s get started.

**The basics of computing**

Most computers use a binary system. That means their code, at its most basic level, is made up of strings of 1s and 0s.

These essentially represent on or off. And using different combinations of these on and offs, you can represent any number.

For example, the number 346 in binary is 0101011010. It’s not important that you know how that is worked out, but just that you know binary can be used to represent any number.

**The basics of quantum mechanics**

At computing’s smallest level it comes down to binary.

At an object’s smallest level – the quantum level – it comes down to waves and particles. Is something a wave, or is it a particle?

In the world of quantum mechanics, it is both.

Light, which is made up of photons, can act as either a wave or as a mass of particles.

And until someone observes it, it is both.

That may sound crazy, but it has been proven many times over with the double slit experiment.

The mere fact you observe it changes its state. Until then it exists in both states. This is called superposition, and it is key.

And to make superposition seem more tangible, I’ll give you the infamous Schrödinger’s cat thought experiment.

**Schrödinger’s cat and superposition**

Schrödinger’s cat is a thought experiment, devised by Austrian physicist Erwin Schrödinger in 1935.

Imagine a cat in a large steel box.

Inside the box with it is a glass vial of poison gas.

Above the glass vial a hammer is suspended by a piece of string.

That string will be severed when a random event happens – when a radioactive particle decays – and the cat will be killed by the poison gas.

The radioactive particle follows quantum laws. So it is either decayed or not decayed. But until you observe or measure it, both outcomes are equally valid.

This means the cat – whose fate is tied to that particle – is both alive and dead at the same time.

The cat is in superposition of being both alive and dead.

**Combine superposition and binary and you get quantum computing**

So, while normal computers can only represent 1 and 0, a quantum computer represents both at the same time, thanks to superposition.

This means it can approach problems in a different way. It doesn’t have to work on one problem after another. It can work on all problems at the same time.

It is not tied to an either or. It has either or and maybe.

For example, if a normal computer wanted to escape a maze, it would try one path at a time until it found the exit.

A faster computer could run down these paths faster than a slower one and so find the way out faster.

But a quantum computer could try all the possible paths at the same time and find the exit instantly.

**Why quantum computers can process exponentially faster**

Okay, so we know quantum computers can represent both 0 and 1 at the same time. But what does that mean practically?

A bit is one bit of information. In a normal computer it’s a 0 or a 1.

A two-bit computer can have four possible combinations of numbers: 00 01 10 11, but it can only represent one combination at any one time.

A two-bit quantum computer can represent all four combinations at the same time, thanks to superposition.

So a two-bit quantum computer is like having four normal two-bit computers running side by side.

This means that as you add more bits to a quantum computer, it speeds up at an exponential rate.

**Why quantum computers can crack codes instantly**

So, let’s say you have a normal 64-bit computer.

That computer can represent 2^{64 }states. Which is: 18,446,744,073,709,600,000 possibilities.

But it can only represent each of these states one at a time. A quantum computer can represent all of them at the same time. This is why they are so suited to breaking cryptography.

So, for instance, a modern computer can cycle about two billion combinations per second.

So in a password-cracking scenario, it would take around 400 years to crack a 64-bit code.

A 64-bit quantum computer could try all 2^{64 }combinations instantly and break a code a normal computer would essentially find impossible.

Before we get carried away, I should state that a quantum computer powerful enough to do this isn’t expected for another decade or so.

And right now, many people are working on making cryptography work differently so it is normal and quantum-proof.

In fact, there are a number or cryptos out there today that are already quantum-proof. Off the top of my head, I can think of NEO and IOTA.

**It’s not just about breaking codes**

As you can probably imagine, quantum computing has far more possibilities than just codebreaking.

It will allow people to write entirely different computer programs and run entirely different experiments and simulations.

As physicist Richard Feynman famously said in 1981:

“Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical, and by golly it’s a wonderful problem, because it doesn’t look so easy.”

Quantum computing has the potential to change our understanding of the laws of nature and everything that follows on from that.

In the end, it will bring us much more than codebreaking. It will change everything.

Until next time,

Harry Hamburg

Editor, *Exponential Investor*

PS I got most of the information about quantum computing from Cosmos magazine’s website. I read around a lot and this was definitely the most coherent and simple explanation I could find on quantum computing. So if you want to know more about it, I can’t recommend that link enough.

Category: Technology