**Quantum Computers: Introduction**

Quantum computing is a sophisticated approach to making parallel calculations, using the physics that govern subatomic particles to replace the more simplistic transistors in today’s computers. Quantum computing harnesses the phenomena of quantum mechanics to deliver a giant leap forward in computation to solve specific problems, and it could represent a fundamental change from the way we process information today.

Experts are already looking into ways quantum computing could be used in areas like financial services, chemistry, artificial intelligence, and so many recent advancements in technology.

**Why do we need Quantum Computers and Moore’s Law?**

Moore’s law is an observation and projection of a historical trend. Rather than a law of physics, it is an empirical relationship linked to gains from experience in production. Moore’s law observes that the number of transistors in a dense integrated circuit (IC) doubles every two years.

Since the 1960s, the power of our brain machines has kept growing exponentially, allowing computers to get smaller and more powerful at the same time. But this process is about to meet its physical limits as Computer parts are approaching the size of an atom.

To understand the problem, let us look into transistors. A transistor is the simplest form of a data processor in computers, basically, a switch that can either block or open the way for information coming through. Transistors are combined to create logic gates that still do straightforward stuff.

For example, an AND Gate sends an output of 1 if all of its inputs are 1 and an output of 0 otherwise.

Combinations of logic gates finally form meaningful modules, say, for adding two numbers. In short, a transistor is just an electric switch. Electricity is electrons moving from one place to another. So, a switch is a passage that can block electrons from moving in one direction. Currently, transistors are around 10-20 nanometers in scale and are expected to shrink to approximately 5-7 nanometers in the next few years, but that’s seemed to be about far as we can go. At that point, transistors are so tiny that quantum effects prevent them from working properly. We are approaching an actual physical barrier for our technological progress.

Scientists are trying to use these unusual quantum properties to their advantage by building quantum computers to solve this problem.

###### Quantum Computing – How it works and what does it solve?

Quantum computers calculate using qubits, computing units that can be on, off, or any value between, instead of the bits in traditional computers that are either on or off, one or zero. The qubit’s ability to live in the in-between state — called superposition — adds a powerful capability to the computing equation, making quantum computers superior for some kinds of math.

For example, today’s computers use eight bits to represent numbers between 0 and 255. Thanks to features like superposition, a quantum computer can use eight qubits to represent every number between 0 and 255, simultaneously.

Twenty of them can already store a million values in parallel. A peculiar and unintuitive property qubit can have is Entanglement. This close connection makes each qubit react instantaneously to a change in the other’s state, no matter how far apart. This means when measuring just one entangled qubit, you can directly deduce its partners’ properties without having to look.

A typical logic gate gets a simple set of inputs and produces one output. A quantum gate manipulates an input of superpositions, rotates probabilities, and produces another superposition as its output.

So a quantum computer sets up some qubits, applies quantum gates to entangle them and manipulate probabilities, then finally measures the outcome, collapsing superpositions to an actual sequence of 0s and 1s. This means that you get the entire lot of calculations that are possible with your setup, all done simultaneously.

Ultimately, you can only measure one of the results, and it’ll only probably be the one you want, so you may have to double-check and try again. But by cleverly exploiting superposition and Entanglement, this can be exponentially more efficient than would ever be possible on a typical computer.

In some areas, quantum computers are vastly superior. One of them is database searching.

To find something in a database, a typical computer may have to test every single one of its entries. Quantum computers algorithms need only the square root of that time, which is a massive difference for large databases.

Using Grover’s search on a quantum computer, you would find the item after checking roughly √N of them. This represents a remarkable increase in processing efficiency and time saved. For example, if you wanted to find one thing in a list of 1 trillion, and each item took 1 microsecond to check:

Classical computer: About one week

Quantum computer: About 1 second

**Quantum Computing and CyberSecurity**

Quantum computers could change how we approach cybersecurity. We’re considering how quantum could disrupt the very basis of today’s encryption methods and impact cryptography standards. I know it can be pretty easy to think I’ve got plenty of time quantum computing is years from mature, but that’s only partially true. Yes, quantum computers are in the early stages of development. Still, the reality is the time to prepare was yesterday because encrypted data stolen today could eventually be in the hands of cyber attackers wielding more advanced quantum computers tomorrow, but fortunately, there’s help. Researchers are now developing alternative methods designed to protect data as quantum computing progresses, and these new methods could change the way we approach cybersecurity.

We’re gaining these new understandings of applying safe quantum cryptography to help protect systems and data against current and future attacks. It’s honestly never too early to prepare companies today to start understanding the potential impact on their sensitive data and educate their security teams on quantum computing and safe quantum cryptography.

If you are interested, you can view this video on – How Quantum Computers Break Encryption

**Quantum Computers will replace Classical Computers?**

Quantum Computers are not universally faster. They are only quicker for particular types of calculations. You can use the fact that you have all these quantum superpositions available to you simultaneously to do some computational parallelism. Suppose you want to watch a video in high definition or browse the internet or write some documenting work. In that case, they will not give you any particular improvement if you need to use a classical algorithm to get the result.

So it would help if you did not think of a quantum computer as something where every operation is faster. Every process will probably be slower than in the computer you have at your desk. But it is a computer where the number of procedures required to arrive at the result is exponentially small.

So the improvement is not in the speed of the individual operation. It is in the total number of processes you need to arrive at the result. But that is only the case in particular types of calculations, specific algorithms. It is not universal, so it is not a replacement for a classical computer.

**What’s Next?**

A handful of companies such as Alibaba, Google, Honeywell, IBM, IonQ, and Xanadu operate early versions of quantum computers today. Today they provide tens of qubits. But qubits can be noisy, making them sometimes unreliable. Systems need tens or hundreds of thousands of qubits to tackle real-world problems reliably.

Experts believe it could be a couple of decades before we get to a high-fidelity era when quantum computers are beneficial. You can explore the world of quantum computing for free on the IBM Cloud and learn to write quantum code – starting with absolutely zero experience.

You don’t have to know how quantum computers work to use them; however, the science is fascinating because it represents so many advanced fields coming together.

#### Pulkit Gupta

Pulkit Gupta is an Associate Application Engineer at Hexaview. He likes to know about how things work and to understand the underlying Science.