Google claims to have achieved “quantum supremacy.” This means that it can solve a problem faster than a supercomputer (the most powerful computer of the moment). But … is this claim correct and do we benefit from this?

Before we go into depth it might be a good idea to go back to the beginning. Earlier you could read here and here what a quantum computer is and what the possibilities are. In the same articles, however, we also had to conclude that we were not that far that quantum computers could already beat the digital supercomputers.

## Quantum versus digital

What makes a quantum computer so special again? To understand this, we must first know what our daily digital computer does. You are currently reading this text from a screen of a digital computer (yes, your smartphone is, in fact, a digital computer), which converts a huge series of bits into a readable text on your interactive screen. Everything a digital computer does is ultimately determined by a lot of bits. These bits are, as it were, the building blocks of computers and in fact nothing else than circuits of 1-bits and 0-bits (on or off).

A quantum computer works differently because it has qubits as building blocks. Instead of 1 or 0, these are both values at the same time, because we use the bizarre physics of quantum mechanics (the language of nature of the smallest particles), where things can be located in different states at the same time. For example, a parallel calculation by one qubit is possible. An example: imagine you have to find the shortest route of a maze. A digital computer tries out all the possibilities, while a quantum computer can try out all the possibilities at the same time and so comes to the right solution much faster. This sounds like the quantum computer should simply beat a digital computer, but this is not the case. The big problem with a quantum computer is keeping a qubit stable. Environmental factors can easily influence a qubit, so that a qubit is no longer 1 and 0 at the same time, but collapses and becomes 1 or 0 before the calculation is finished. That is why a quantum computer functions best around absolute zero in an isolated space.

Quantum computers have not yet been able to beat a digital computer. As soon as this succeeds, we talk about quantum supremacy.

Now Google claims that it has achieved this quantum supremacy with a quantum computer with a chip with 53 qubits, called “Sycamore”. This number of qubits can use 253 possible combinations of rows with 53 1s and 0s simultaneously for its calculations. The processor of this computer takes 200 seconds to complete a calculation that a digital computer according to Google would take ten thousand years. According to the makers, this was only achieved by chance, while testing their new quantum processor. This quantum supremacy took place in a calculation in which it was checked whether a set of numbers was really randomly distributed. Furthermore, there is no applicable utility of this calculation, because it was really only meant to test the capacity of the quantum computer compared to the digital computer.

## Criticism

Google’s result is good news for the scientific world. For example, physicists involved in quantum mechanics once again confirm that the theory of quantum mechanics describes reality and has useful applications. In addition, it will also attract new computer scientists and engineers to further investigate quantum computers.

“It is also argued that quantum supremacy is only really achieved if a quantum computer is able to perform tasks that a supercomputer is not even capable of”

Competitor IBM contradicts Google and says that the supercomputer would not take 10,000 years, but only 2.5 days. This is still slower than 200 seconds, but IBM is questioning Google’s credibility here. In addition, it is also argued that quantum supremacy is only really achieved if a quantum computer is able to perform tasks that a supercomputer is not even capable of. Not even in 2.5 days or 10,000 years. Furthermore, IBM also questions quantum supremacy as a criterion for testing the superiority of the quantum computer. IBM proposes to look at quantum volume. This also takes other factors into account, such as how well qubits can cope with errors and how long they can retain their quantum properties.

Google agrees with the fact that many steps still need to be taken for a stable quantum computer. In their article *Nature,* the researchers also point out that in the future there will have to be more focus on correcting errors – so-called “*quantum error correction*’Algorithms – to make quantum computers more reliable.

## Competition

*IBM is not only a competitor of Google. Microsoft and Intel are also working with a lot of scientists on quantum computer technology. In addition, a lot of research is being done at universities and, for example, TU Delft is a forerunner in the field of quantum computers.*

## Opportunities

Google’s calculation was not yet a useful one, but in the future, the quantum computer could be used to solve problems where a digital supercomputer fails. Keep in mind that this first step is only a small step and that it may well take decades before we will have a fully-fledged reliable quantum computer in the world. Nevertheless, we can of course start thinking ahead. For example, physicists believe that with a quantum computer physics itself can be simulated, since quantum mechanics is the language of the building blocks of our universe. In addition, we can also think of simulating chemical reactions, with which new medicines can be developed. Quantum computers can also help in the further development of artificial intelligence and make calculations with neural networks. In the wrong hands, however, quantum computers can also be used to easily crack the encryption of digital computers, because a quantum computer can be very good at factorising large numbers. That is why we are already thinking about how banks, government agencies, etc., can prevent these hackers by making encryption better with quantum computers. Bitcoin technology will also have to take this into account, as it is also based on cryptography.

The question is whether the quantum computer will eventually end up in our living room. Since a quantum computer only functions under extreme conditions, it is more likely that we will see a collaboration between digital and quantum. Think of having a digital system at home and the possibility to use a quantum computer remotely for tasks that can best be performed by a quantum computer. All in all, Google has taken a big step towards a new era in which quantum computers can control our lives.