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What is Quantum Computing?

September 24, 2017

While quantum physics itself remains elusive to the vast majority of people, its practical applications are astounding in their gravity. Perhaps the most famous of such applications is that of the quantum computer, an invention which could have the capacity to revolutionise the world of technology. 

 

Now, while the idea has indeed captured the eyes of many in popular media, the actual physics behind such a system seem to be largely unknown. 

In this article, I shall explore the workings behind such a system.

 

Computers and their parts have been getting smaller and more efficient for years. From huge transistors the size of your palm, down to half the width of the ebola virus. 

As our technology continues to develop, we see this trend continuing - but soon we are going to hit a very serious threshold. 

 

Computer systems are approaching the size of atoms. 

 

Why would this be an issue? Well, as these systems approach the size of atoms, quantum physics - in all its weirdness - comes into play. Particles stop behaving in their classical manner, and instead start to do all sorts of weird tricks and stunts. 

For example, they can conduct what's called "quantum tunneling" - essentially just dodging a transistor gate entirely. 

 

So is that it? Have we really reached the size limit of our computers?

 

Classical computers - yes. Quantum computers - not remotely. 

Quantum physics can be used to our advantage rather than our detriment. 

 

Classical computers work based on these little harbingers of information - bits - existing as either '0' or '1'.

Electrons in a quantum computer also have their own two level system called 'spin'. Electrons, when placed under a magnetic field, can be made to orient their direction depending to the amount of energy they posses.

An electron in the ground state (lowest energy level) when placed under the influence of a magnetic field, would turn downwards. If the electron possessed enough energy, it would point upwards. These properties are known as 'spin up' and 'spin down' (to find out more about quantum mechanical spin, click here).

 

However, one very special property of quantum objects is that they can be in both states at any one time. This is known as a 'superposition'. Once we measure the electron's spin, it will collapse into either the up or down state - but before that, it will exist as both.

 

Electrons existing in superposition can be hugely helpful to us - as it means that 'n' number of electrons can have 2 to the power of 'n' combinations.  As n approaches 300, for example, the number of combinations approaches the number of particles in the universe!

 

Due to this exponential power, huge and very complicated processes can be done far more efficiently by a quantum computer than a classical computer.

This is where the true power of quantum computers lie.

 

But who cares? What's the point of quantum computers anyway?

 

First, let's look at encryption.

Currently, most encryption tools use the power of prime numbers. One long string of numbers is sent out from one computer as a 'key', but in order to decode information, you would need to know the two prime factors of this number.

For example, my computer may send out the number 15, and in order to decode my information you would need to know that the prime factors are 3 and 5. 

As these numbers get longer and longer, finding the prime factors may prove to be extremely difficult. 

If I were to send out, say, the number 3864788610093876213423256313, finding the prime factors would be fairly hard. 

Classical computers take years to find such factors, as the trial and error process is long and arduous. 

Quantum computers, however, with their 2 to the 'n' combinations, are far more efficient and take a fraction of the time.

 

Creating very complicated protein models is also far easier for quantum computers than for classical computers. So too are quantum models, as the complexity of quantum systems may prove far too difficult for a classical computer to handle. 

Database searching is, also far easier with a quantum computer. Searching for individual inputs in a vast database would be much quicker using a quantum system than a classical one. 

 

But don't be mistaken. Classical computers aren't going out of fashion any time soon. 

 

Quantum computers need to be pampered and maintained, and they are only useful for huge and complicated problems. When it comes to watching netflix, scrolling through facebook or browsing reddit - they're no use. 

 

 

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