A quantum computer is a new computer architecture that uses quantum mechanics to perform certain kinds of calculations. These computations are much more efficient than the computer we are used to today (let’s call it “classical”). How they work (and why they don’t work) – read the book “AI-2041”.

## Superproperties of qubits

Classic computers operate with bits – it is the smallest particle, so to speak, the “atom” of information. A bit is like a switch – it can be either zero (if off) or one (if on). Every application, web site or photo consists of millions of such bits. The use of binary bits simplifies the representation of data and the control of classical computers, but it also limits their potential to solve truly complex computer science problems.

A quantum computer uses quantum bits, or qubits; these are usually subatomic particles such as electrons or photons. Cubits “live” by the principles of quantum mechanics, and their properties are quite unusual, they can even be called “superproperties.

The first of them is superposition, the ability of a qubit to be in several states at any given time at once. Because of this, several qubits in superposition can simultaneously process a huge amount of data.

An AI solving the problem of winning a computer game on a classical computer will go through different moves and try them out, “twist” them until it finds a way to win. An AI built on quantum computing will try all the moves much faster (and therefore more efficiently), and it will also take into account the probability of error, all of which exponentially reduces the complexity of the process.

The second unusual property of a qubit is entanglement (interdependence). Any two qubits in a quantum computer are always interconnected – and actions performed on one affect the other, even if the qubits are very far apart. Due to entanglement, each qubit added to a quantum computer (it can be done by software methods) increases the computational power of the machine exponentially.

To double the power of a classical $100 million supercomputer, you have to shell out the same amount of money; and you can double the power of a quantum computer simply by adding another qubit.

## The downside

But of course there is a downside to these amazing properties. Quantum computer is extremely sensitive – it is affected by the smallest hardware failures and even environmental changes. Vibrations (from a nearby streetcar), electrical disturbances, temperature changes or magnetic waves can weaken or even eliminate the superposition.

To build a workable and expandable quantum computer, it is necessary to invent new technologies and create unprecedented vacuum chambers, superconductors and supercoolers – the only way to minimize losses due to environmental influences.

Scientists have managed to increase the number of qubits, although it took a very long time; in 2020 there will be 65, compared to two in 1998. But there are still too few of them to do anything really useful for humanity. Chips with 433 qubits are planned for 2022 and 1,121 qubits for 2024. However, even on a few dozen qubits, some computational tasks go millions of times faster than on classical computers.

In 2019, Google demonstrated this “quantum superiority.” A 54-qubit quantum computer solved a problem in minutes (though completely useless – “experimental”) that would have taken classical computers years.

One of the applications of a functional quantum computer which will definitely change our world for the better will be the development of new drugs

. Modern supercomputers can only analyze basic molecules, but their total number, suitable for creating an effective drug, is exponentially greater than the number of all atoms in the observable universe.

Problems of this magnitude require quantum computers based on the same quantum properties of the molecules they will model. Such computers will be able to simultaneously create new compounds, simulate complex chemical reactions involving them and evaluate their effectiveness for treating various diseases.

A quantum computer will be able to make predictions that are beyond the capabilities of a classical computer: to suggest ways to counteract climate change; to predict pandemic risks and the consequences of inventing new materials; to explore space; to model human brain activity; to understand quantum physics.

From the book AI-2041.

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