# Fundamental of quantum computers

# What are quantum computers?

Quantum computers could stimulate the development of an important discovery in various fields. Here is everything you need to know about quantum computing. It can be a major breakthrough 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.

We experience the benefits of classical computing every day. However, there are challenges that systems that are here today will never be able to solve. For problems above a certain threshold, we don’t have enough computational power on Earth to solve them.

For tackling some of these problems, we need a new kind of computing. Universal quantum computers leverage the quantum mechanical phenomena of superposition and entanglement to create states that scale exponentially with the number of qubits, or quantum bits. All computing systems rely on a fundamental ability to store and handle information. Current computers handle individual bits, which store information in binary as 0 and 1 states. Quantum computers leverage quantum mechanical phenomena to handle information. For this, they rely on quantum bits or qubits.

**Top of form bottom of Form Are We Ready for Quantum Computers?**

A recent paper by Google claiming that a quantum computer performed a specific calculation that would choke even the world’s fastest classical supercomputer has raised many more questions than it answered.

Google achieved this milestone against the setting of more serious reality. Even the best gate-based quantum computers today can only muster around 50 qubits. A qubit, or quantum bit, is the basic piece of information in quantum computing, analogous to a bit in classical computing but so much more.

Gate-based quantum computers work on the principles of logic gates but, in contrast with classical computers, they change the inherent properties of quantum mechanics such as superposition, interference, and entanglement. Current quantum computers are so loud and error-prone that the information in its quantum state is lost within microseconds through a mechanism called decoherence.

Still, researchers are making working on demonstrations, if slow, progress toward more usable qubits. Perhaps in 10 years, or 20, we’ll reach the goal of reliable, large-scale, error-tolerant quantum computers that can solve a wide range of useful problems.

# When that day comes, what should we do with them?

In the early 1980s, the American physicist Paul Benioff published a paper demonstrating that a quantum-mechanical model of a Turing machine — a computer — was theoretically possible. Around the same time, Richard Feynman argued that simulating quantum systems at any useful scale on classical computers would always be impossible because the problem would get far, the required memory and time would increase exponentially with the volume of the quantum system. On a quantum computer, the required resources would rise up far less radically.

Feynman launched the field of quantum computing when he suggested that the best way to study quantum systems was to simulate them on quantum computers. Simulation quantum physics is *the *app for quantum computers. They’re not going to be helping you stream video on your smartphone. If large, fault-tolerant quantum computers can be built, they will enable us to probe the strange world of quantum mechanics to unparalleled depths.

On a quantum computer, we could simulate quantum field theories to study the most fundamental nature of the universe. In chemistry, we could investigate the basic properties of materials and design new ones to understand mechanisms such as unconventional superconductivity. We could simulate and understand new chemical reactions and new compounds, which could aid in drug discovery.

By diving deep into mathematics and information theory, we already have developed many theoretical tools to do these things, and the algorithms are farther along than the technology to build the actual machines. It all starts with a theoretical model of the quantum computer, which establishes how it will harness quantum mechanics to perform useful computation.