# Scoop: QTFT webinar “quantum computing in a nutshell”

*This article is written by Tonklar Khaimuk, a high school student at Mahidol Wittayanusorn School, Thailand, with the supervision of the QTFT team. The content is inspired by the QTFT webinar**“quantum computing in a nutshell”**by Jirawat Tangpanitanon, Areeya Chantasri, and Thiparat Chotibut.*

In our everyday life, we have experienced quantum technology 1.0, from electronic systems, phones, notebooks to GPS, satellite and more. However, these technologies only exploit partial properties of quantum mechanics.

Fueled by Nobel-winning experiments, we are now in the age of quantum technology 2.0 or the “second quantum revolution”, where individual atoms and photons can be manipulated. Applications include quantum computing, quantum simulation, quantum communication, and quantum sensors. A 10-year European quantum flagship has been launched last year. Many private companies including Google, IBM, Microsoft, Intel, Alibaba, Huawei, etc. and governments have funded billions of dollar to research in quantum technologies.

So why is this field of science so important and how could it potentially disrupt the way technologies are now? In this article, we will address these questions, focusing on quantum computing.

**Our limit**

Moore’s Law, indicated by the former CEO of Intel Gordon E.Moore, has told us about the limit of the existing processing chips. As the speed of the chips grows with an exponential rate, the size has to decrease with an exponential rate too. In less than 10 years, we will not be able to make smaller chips because they will eventually reach the size of atoms.

The end of the Moor’s law raises a major concern since data on the internet is growing at an exponential rate. If the hardware does not get faster, we will not be able to process overwhelming-large data in the coming future. Quantum computing provides a possible way out of this.

**Quantum computing: pushing the limit**

For centuries, quantum physics have been used to explain the weird properties of the atomic world. By exploiting these properties in computation, a quantum computer can have a drastic speedup compared to the conventional or ‘classical’ computer.

Here, we will talk about quantum superposition, the simplest example of quantum properties. Quantum superposition is the situation in which a particle can be in two states at the same time. Erwin Schrödinger, a Nobel Prize-winning Austrian physicist and a co-founder of quantum mechanics, explains this in a classic thought experiment known as Schrodinger’s cat experiment. Imagine a cat in a black-box with a radioactive substance inside. When the substance decays, it triggers a hammer. The hammer will then hit a poison bottle. According to quantum mechanics, the substance can be in a superposition of decaying and not decaying at the same time. Hence, the cat’s state can also be dead and alive at the same time. We could not know the cat’s state until we observe it. When we open the black-box, these two states will collapse into one. We then know whether the cat is dead or alive. This situation happens to, for example, an electron spin which can be in a superposition of two states; spin up or spin down.

In quantum computing, we can create a bit which is quantum, known as “qubit”. It means that this bit must have the quantum superposition property. The classical bit can be either 0 or 1. But a qubit can be both 0 or 1 with some probabilities, like a “quantum coin” that can be head or tail at the same time.

To understand how quantum superposition can be exploited in computation, imagine a problem where we have a maze and we want to find an exit. A classical computer would need to try a possible path to find the solution at a time. However, a quantum computer has many states to help to find the path simultaneously.

A large class of optimization problems such as drug design, efficient logistics, big data can be mapped to the above problem. In most cases, the number of trials that a classical computer have to try will increase exponentially with the size of the system. However, a quantum computer can take only polynomial or linear number of trails to find the solution, leading to a drastic speedup in computation.

**Reaching quantum supremacy**

Nowadays, everyone can use a 5-qubit quantum computer online at the IBM quantum cloud for free. A 20-qubit machine is available with some fees. It is estimated that a quantum computer with 50–100 qubits will be able to perform computational tasks that are intractable for existing supercomputers- the ability referred to as quantum supremacy. Big tech companies like Google and IBM as well as research institutes worldwide are now in the race for quantum supremacy which is expected to be achieved in a few years time. However, these quantum devices are currently noisy. Hence, operations that can be performed on the devices are severely limited. Even after when quantum supremacy has been realized, scientists still have to figure out how to use these noisy near-term devices to solve real-world problems.