## Table of contents:

- Why transistors can't get smaller
- How does a quantum computer work?
- How does a quantum computer calculate?
- What a quantum computer can do
- What is the current status of quantum computers?

## Video: The Development Of The Quantum Computer

2023 **Author**: Hannah Pearcy | [email protected]. Last modified: 2023-06-05 00:21

If you want to describe a quantum computer and its capabilities, it sometimes sounds as if you were describing magic - because in the quantum domain our understanding of physics no longer applies. In order to understand quantum computers at least in the beginning, one should first take a look at classic computers: A computer is based on the smallest electronic circuits, which in turn are embedded in microchips, so-called integrated circuits (ICs), which contain active and passive components, cables and **transistors - tiny electronic switches and the smallest functional unit in a computer**.

## Why transistors can't get smaller

A transistor **works like a switch:** it uses voltage potentials to represent a state - either 0 or 1, the smallest binary unit in a computer, the so-called bit. Transistors are linked together to create logic gates. Linked together, these logic gates can perform the simplest arithmetic and storage operations. These simple circuits are sufficient to carry out the highly complex applications that today's modern computers can achieve.

To achieve more performance, computer technology has been miniaturized for decades. Today, transistors are unimaginably small at **just 10 nanometers** - 18 billion transistors fit on a chip measuring two to two centimeters.

But now a physical limit in miniaturization has been reached. On the one hand, the current manufacturing methods using ultraviolet light are no longer sufficient to produce even smaller transistors. And on the other hand, transistors that are only a few atoms in size have **strange physical conditions** that, in our opinion, should not be possible: Although a physical barrier in the transistor can prevent the electrons from progressing, they do it on this small scale to pass the barrier. This **tunnel effect** is also called the **quantum mechanical effect** and prevents classic computers from being further miniaturized.

But researchers want to take advantage of this effect to develop so-called quantum computers.

## How does a quantum computer work?

In quantum computers, the smallest unit of information is not the bit, but the **quantum bit**, or qubit for short. A classic bit has the clearly defined state 1 or 0. The qubit also knows the states 1 and 0, but in contrast to the conventional bit, the qubit has both states at the same time, so it is not limited to one state. This property is called **superposition**.

**And here it gets exciting:** The state of the superposition only remains as long as the qubit is not observed. However, the moment the state of the qubits is determined, it takes on a clearly defined state - 1 or 0 - with a certain probability.

The computing power of quantum computers is also clear here: In a classic computer, four different combinations (00, 11, 10, 01) can be represented with one bit, from which one can choose - but with a qubit, **all four combinations can be** used **simultaneously** become. In addition, their superposition enables qubits to perform **parallel arithmetic** operations - and each additional qubit multiplies that exponentially.

A second remarkable property of quantum computers is **entanglement**. Two qubits that are intertwined have a connection between them - regardless of their distance. Even over thousands of kilometers, the qubit takes on the state of its entangled qubit, without any time delay.

## How does a quantum computer calculate?

As already described, classic computers use logic gates for calculations. So-called **quantum gates are** used in quantum computers and although these gates differ enormously, the same arithmetic operations can be carried out - with the groundbreaking difference that a quantum computer can carry out these calculations simultaneously.

## What a quantum computer can do

**Encryption:** This ability can actually pose a **threat to our IT security**, especially for current cryptographic encryption methods. The prime factorization is a common encryption and is considered very secure. A number is created by multiplying several prime numbers. To restore the original prime numbers, current computers would take 100,000 years. Since quantum computers can perform arithmetic operations in parallel, they would be able to crack this encryption within minutes using the so-called Shor algorithm. This would involve encryption of e-commerce platforms, cloud offerings, e-banking, IoT systems and everything that is transmitted in encrypted form on the Internet.

The good news is that quantum computers also enable a new type of encryption, quantum cryptography. Nevertheless, security experts are already warning today of thinking about possible quantum computers in the future - especially with sensitive data that has been stored for decades, such as bank data, there is a risk that the advent of quantum computers will quickly crack the old encryption.

**Databases:** Another application of quantum computers is the **search in gigantic databases** using the Grover algorithm. While a classic computer searches a database entry by entry, the quantum computer can scan the entries much faster due to its superposition.

**Simulations:** Even highly complex simulations, for example of quantum technology itself or of complicated molecular structures, can benefit from quantum technology, because conventional computers reach their limits here.

#### Technology explained briefly

### The development of the Einstein elevator

## What is the current status of quantum computers?

Both research institutions and companies are currently building quantum computers, although completely different architectures are still used here. Google and IBM separately build a quantum computer based on **superconducting stripline resonators**. A qubit is an electron cloud inside a microwave oscillator. This is cooled down to 15 millikelvin, which is close to zero. A Josephson contact offers the possibility of quantum tunneling, and by adjusting the oscillator frequency, the qubits can be interleaved and quantum gates can be used.

Last year, Google caused a sensation by introducing **its first quantum computer**, which performed a calculation in minutes that traditional computers actually took 10,000 years to do. This calculation was carried out with 53 qubits. As the next step, Google wants to implement **a chip with 1,000 qubits** - however, the amount of qubits is not the only decisive factor for the computing power, the qubits must also be of high quality in order to have a low error rate.

How important quantum computers will become for our future can hardly be said at the moment. Research on the quantum computer is still in its infancy. It is unlikely that they will replace our classic computers, but in which direction the development is going and what the next quantum leap will be - in this context, a Janus word, because a physical quantum leap is something tiny and small - is uncertain.