# Quantum Computer and Applications

### Quantum Computing: an Ongoing Process

**- The Fundamental Physics Driving Quantum Computing**

Quantum computers aren’t the next generation of supercomputers - they’re something else entirely. Before we can even begin to talk about their potential applications, we need to understand the fundamental physics that drives the theory of quantum computing.

A quantum computer is a device performing quantum computations. It manipulates the quantum states of qubits in a controlled way to perform algorithms. A universal quantum computer is defined as a machine that is able to adopt an arbitrary quantum state from an arbitrary input quantum state. The development of a quantum computer is currently in its infancy, systems consist of a few to a few tens of quantum bits (qubits). Main challenges in further development are to make the quantum computer scalable and to make it fault-tolerant. This means that it will be able to perform universal quantum operations using unreliable components. The production of a working quantum computer has become a real possibility, thanks to recent developments in the nanotechnology field, but there is still a long way to go.

The field of quantum computing focuses on the development of computer technologies based on the principles of quantum theory. Quantum theory explains the behavior and nature of matter and its energy at the quantum level. Quantum computers can handle more than just the binary information which conventional computers operate on. Quantum computers can also handle data in between a 0 or 1 bit, which should, in turn, provide new types of simulation and calculations.

In quantum computations the spin direction, which is either up or down, serves as the basic information unit which is similar to the 0 or 1 bit in a classical computing system. Electron spin can assume both 0 and 1 simultaneously, as a result of quantum entanglement, which greatly enhances the ability to perform complex computations.

**- A History of the Future**

In 1936, Alan Turing proposed the Turing machine, which became the foundational reference point for theories about computing and computers. Around the same time, Konrad Zuse invented the Z1 computer, considered to be the first electromagnetic binary computer. What happened next is history, and in our world today, computers are everywhere.

The major catalyst behind this transformation was the discovery of silicon, and its use in the production of good transistors. This occurred over a period of more than 100 years, dating from when Michael Faraday first recorded the semiconductor effect in 1833, via Morris Tanenbaum, who built the first silicon transistor at AT&T Bell Labs in 1954, to the first integrated circuit in 1960.

We are about to embark on a similar journey in our quest for building the next-generation computer. In the early 1980s, Richard Feynman, Paul Benioff and Yuri Manin provided the groundwork for a completely new paradigm of quantum computing, introducing the idea that quantum computing had the potential to solve problems that “classical computing” could not. And so quantum computing came into its own. Quantum computing could change the world. It could transform medicine, break encryption and revolutionize communications and artificial intelligence.

Quantum physics, which emerged in the early 20th century, is so powerful and yet so unlike anything known before that even the inventors had a hard time understanding it in detail. Similar to the trajectory of non-quantum communication, which took more than 100 years from discovery to mass use, quantum computers are now maturing very quickly. Today, many players are engaged in a battle over who can build the first powerful quantum computer.

**- Quantum Supremacy**

In October 2019, researchers at Google announced to great fanfare that their embryonic quantum computer had solved a problem that would overwhelm tthe dawn of the agehe best supercomputers. Some said the milestone, known as quantum supremacy, marked of quantum computing.

The goal of quantum computing is to provide a rapid, secure connection that can instantly send packets of quantum information to computers around the world. The beauty of it is that it’s unhackable - a quality many world leaders find incredibly desirable. The promise of quantum computing seems limitless - faster Internet searching, lightning-quick financial data analysis, shorter commutes, better weather prediction, more effective cancer drugs, revolutionary new materials, and more.

Quantum computers could spur the development of new breakthroughs in science, medications to save lives, machine learning methods to diagnose illnesses sooner, materials to make more efficient devices and structures, financial strategies to live well in retirement, and algorithms to quickly direct resources such as ambulances. However, most of the big breakthroughs so far have been in controlled settings, or using problems that we already know the answer to. In any case, reaching quantum supremacy doesn’t mean quantum computers are actually ready to do anything useful. Researchers have made great progress in developing the algorithms that quantum computers will use. But the devices themselves still need a lot more work. Quantum computing could change the world - but right now, its future remains uncertain.

**- Quantum Software and Algorithms**

The field of quantum computing started in the 1980s. It was then discovered that certain computational problems could be tackled more efficiently with quantum algorithms than with their classical counterparts.

In quantum computing, it’s not just the computers themselves that are hard to build. They also need sophisticated quantum algorithms - specialized software that’s tailored to get the best out of the machines. Since the field of quantum computing is so new, only a small band of experts today can create advanced software that will work on the machines.

The excitement around quantum computers stems from the fact that instead of digital bits, which represent either 1 or 0, they use “qubits,” which can be in both states at once thanks to a phenomenon known as superposition. Another almost mystical quality, called entanglement, means that qubits can influence one another even if they’re not physically connected.

Adding extra qubits exponentially increases the computing power of quantum machines, which may soon be able to outperform even the top supercomputers at a limited range of tasks. That’s the good news; the not-so-good news is that qubits tend to lose their delicate quantum state after mere milliseconds. Changes in temperature, or even the tiniest of vibrations, can also disrupt them and throw errors into their calculations.

This is where quantum algorithms come in. They run a specific calculation on a quantum machine as quickly and efficiently as possible, and they can often help mitigate errors. “Think of it like tuning a guitar,” says Aspuru-Guzik. “Just as you adjust the strings so they’re in harmony, we can play with various parameters until a quantum circuit is tuned for a particular application.

**<More to come ..>**