A Moore’s law (popularized as such but not really related to Moore’s observations) says that every 18 months a breakthrough occurs in technologies. For example, that a characteristic is twice as efficient, like power, capacity, speed, etc.

What if the quantum computer revolutionized technologies in this way?

It would pose a lot of problems for the encryption systems, or ciphers, that are already in place, and that protect the confidentiality of data.

### What is a quantum computer?

A quantum computer is almost like a computer with one fundamental difference.

A computer to send and receive information uses 0’s or 1’s. These are bits.

A **quantum** computer does not use bits anymore, but its analogue the **qubits**.

This is where it gets complicated. What are qubits?

Qubits use the properties of quantum physics, which must vaguely remind you of your high school classes.

In quantum physics, the same quantum state can have several values for a certain observable quantity. This is difficult to understand, and for good reason, we are not used to it at all in everyday life, it happens in the quantum world, at the atomic and subatomic scale.

### Why is this about the secret?

It’s all about being able to factor numbers with prime numbers, and similar mathematical tasks.

This is the basis of **encryption** nowadays, especially asymmetric encryption.

But only quantum computers are fast and powerful enough to factor numbers and find prime numbers.

Encryption has become extremely important in our societies since it protects confidential documents, state secrets, medical secrets, banking secrets, etc.

### The problem of quantum computers

A quantum computer can only execute one class of algorithm. It cannot do all the tasks.

Moreover, if you have enough qubits, a quantum computer is much faster than a normal computer. But this does not mean that the quantum computer is always more powerful than the classical computer. It could be that a more efficient algorithm makes the classical computer win against the quantum computer.

### When will a quantum computer be able to break encryptions on the Internet?

Today, the best quantum machines can handle several dozen qubits.

According to Brian LaMacchia, who manages security and cryptography at Microsoft Research, a cryptographically interesting quantum computer should be able to handle between 1000 and 10000 qubits. According to him, a machine of this type could be ready between 2030 and 2040.

However, there are confidential data that one would not even want to be revealed in a little more than a decade.

→ General Knowledge: the Secret