Explained: What is Quantum Computing? [2021]

Quantum computing enables the potential of harnessing data almost with supernatural powers. Quantum computers are inspired by the way particles such as electrons and protons behave in nature, and researched by the field of Quantum Mechanics in Physics. 

Quantum computing won’t render your conventional computer obsolete anywhere soon, but they promise to power incredible transformations in fields such as medical research, molecular modeling, AI, cryptography, and more.  

In this article, I will cover some of the most important concepts in quantum computing and why all tech giants are in rush to win the race in Quantum Supremacy. Let’s get started!

What is Qubit?

Regular computers, such as your laptop, desktop, or mobile phone, process data using binary bits, one at a time. A bit can be either 0 or 1.

What is Quantum Computing Qubit
Binary bit in a classic computer

Quantum computers use the same binary paradigm, the difference being a Quantum bit or Qubit can be 0 and 1 at the same time

Bit vs Qubit
Classical Bit vs. Quantum Bit (Qubit). Source: Towards Data Science

Binary bits, quantum bits… still confused?

Hang with me for just a bit! 

I’m sure you had fun flipping coins before. The result of a coin flip can be represented in two ways: head or tails. We can refer to head being 0 and tail being 1. Here you go, you got a binary system, where the results can be either 0 or 1, head or tails. In classical computing, 1 represents an electrical signal, and 0 the absence of it. 

Source: 2Physics

In Quantum computing, a Qubit can be both 0 and 1, head or tails at the same time. Think of flipping a coin that never stops spinning without your help. The probability of being head or tails is 50/50 at any point in time.

In the Quantum world, a particle can be in two or more quantum states at the same time. A quantum state refers to how a particle spins: “up” or “down,” and where it is located: “here” or “there” – when observed. The ability of particles to be everything and everywhere at the same time is called Superposition – a quantum phenomenon that is at the very heart of our reality.

What is Quantum Superposition?

In the context of Quantum Computing, superposition refers to the ability of a Qubit to be in different states at the same time. This means a Qubit can have multiple combinations of 0 and 1 simultaneously. 

Scientists are able to put Qubits into quantum superposition by bombarding them with microwave beams or precision laser. Once the Qubits are in a superposition, a vast array of potential outcomes can be computed simultaneously. 

The final result is generated once the operator decides to measure the Qubits. The process of observing or measuring the Qubits will cause their quantum state to end or “collapse” to either 0 or 1, and the result will be generated. 

And you may wonder why “collapse”? In the Quantum world, you cannot observe a particle without influencing its state. You cannot know its spin and position at the same time. 

If you start getting a headache, you’re not alone. This quantum phenomenon puzzled scientists for nearly 100 years, and it continues to do so as we dive deeper into the very tiny building blocks that construct our reality. I’ll cover more about Quantum states in a future article. 

Quantum Superposition
Source: 25 Hour News

But wait, the weirdness in quantum world doesn’t stop here. 

What is Quantum Entanglement?

Scientists can put a pair of Qubits in a single quantum state called quantum entanglement. In simple words, entangled particles are able to communicate their quantum state instantaneously regardless of how far apart they are. 

Quantum Entanglement
Quantum Entanglement. Source: Science News

Yes, that’s right: if we could entangle two Qubits, one on Earth and another on Mars, and change the Earth Qubit to spin clockwise, the state of the Qubit on Mars will instantly change. Well, in theory at least.

Note that if something can be faster than the speed of light or not is currently a heavy topic for debate among scientists. All the rest of us can do is to wait and see what future research might reveal.

Quantum entanglement baffled even the greatest minds in history, like Einstein, who famously called it “spooky action at a distance.” Regardless of how “spooky” this is, the ability to add extra Qubits to a quantum machine ad tremendous exponential power to its computing capabilities. 

Einstein Spooky Action Quantum
Source: own creation

To work their magic, quantum computers harness entangled Qubits in something like a quantum daisy chain. 

The good news is that specially designed algorithms can speed up calculations on quantum computers millions of times faster than the most powerful machine today. That’s the reason why there is so much buzz around their potential! 

The bad news is something called decoherence, which makes quantum computing way more prone to errors than a classical computer. 

What is Quantum Decoherence?

You should know by now that quantum particles are sensitive to any kind of interference. In a quantum computer, the environment in which the Qubits live can interfere with their quantum behavior and lead to quantum decay. This phenomenon is called quantum decoherence.  

Quantum Decoherence
Source: Hackernoon

When we talk about interference, we can refer to anything like variations in temperature, vibration, or light that can disturb a Qubit’s superposition before its job is completed. In quantum terms, these external factors are referred to as “noise.”

Noise is the main reason why scientists place these super-computers in vacuum chambers and/or supercooled fridges. Regardless of the effort, noise can still interfere and cause errors that render the whole computation useless.  

A way to address decoherence in quantum computing is to develop smart quantum algorithms capable of adding additional Qubits to compensate for quantum decay in a system. 

Of course, the ultimate goal is to create highly reliable Qubits called “logical” Qubits though it may take thousands of standard Qubits to get a single reliable one. 

And you may think, why that’s such a big deal? 

If you think that the largest quantum computer so far contains just 65 Qubits, you will soon understand the challenge.    

 The truth is that quantum computing is still in its very infancy. Something like Alan Turing’s The Bombe. It may take quite a while to untile quantum computers will be broadly available. However, this does not deter scientists from competing for the ultimate goal: Quantum Supremacy.

Final Destination: Quantum Supremacy

Quantum supremacy – sounds like something straight out of Kubrick’s 2001: A space odyssey. In short, quantum supremacy refers to the ability of a quantum computer to solve a problem that no classical machine can solve in a given amount of time. 

However, it is yet unclear how many Qubits such a quantum machine would need, with today’s super-computers getting faster and better at solving problems. 

Google, IBM, Intel, Microsoft, Amazon, as well as several large startups (HoneywellD-WaveRigetti) spent heavily in recent years on quantum computing hardware. IBM, Google, and Alibaba provide access to their latest prototypes over the Internet, while Microsoft and Amazon host a variety of cloud services using quantum hardware built by third-parties.

In December 2020, China announced in the journal Science its own declaration of quantum supremacy when a quantum system called Jiuzhang calculated in minutes a computation that would normally take 2 billion years by the super-computing standards of today. 

Jiuzhang and Google use different quantum computing mechanisms. Google builds its quantum circuits using superconducting, supercold metal while the team from the University of Science and Technology of China manipulates particles of light (photons) as quantum circuits. 

How does a Quantum Computer look like? 

We’ve been talking a lot about how quantum computers work. What about how they look like? 

If you have never seen a picture of Google’s quantum computer before, think of a chandelier made of many wires and copper tubes, hanging on a ceiling. 

That’s why scientists actually call the structure a chandelier. 

China’s Jiuzhang light-based quantum computer looks more like a massive array of lasers that combines their power into a central core. 

Jiuzhang light-based quantum computer
China’s Jiuzhang light-based quantum computer. Source: Global Times

Seeing their massive size, it is hard not to relate to how computers looked like a few decades ago and how much hardware was required to solve a basic computation, as per today’s standards. 

We shall see how long it would take to become the slim quantum device you could carry every day in your pocket. 

 Who will benefit from Quantum Computing first?

One of the most exciting quantum computer applications is to predict the behavior of matter down to the molecular level. Car manufacturers like Volkswagen and Daimler use quantum computers to model electrical-vehicle batteries’ chemical structures to discover new ways to boost their performance. Pharmaceutical firms use them to evaluate and compare substances that could contribute to the development of new medicines.

Machines are also useful for optimization problems since they can cross large possible solutions very rapidly. For example, Airbus uses them to help calculate the most fuel-efficient aircraft ascent and descent routes. And Volkswagen has launched a service that measures the best routes for busses and taxis in cities to reduce congestion. Some researchers still claim that robots could be used to accelerate artificial intelligence.

Quantum Computing Infographic
Source: AIRBUS

Quantum computers could take quite a few decades to reach their full potential. Universities and companies working on them are faced with a shortage of qualified researchers in the field—and a lack of supplies of essential components. But if these exotic modern virtual machines live up to their potential, they might transform whole markets and turbocharge global creativity.

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