quantum computing, century edition?

Since the late 1970s, the idea of ​​creating a quantum computer has been considered by scientists, who claim – even at that time – that this technology will be the real “technological revolution” in the modern world. During the 1990s, people started talking specifically about the quantum computer, but with modest capacities. So during the 2000s, companies announced that they had built superquant computers, which most scientists doubted at the time. But in recent years, public research laboratories as well as leading companies such as IBM, Google or Honeywell have unveiled the first working prototypes of these ultra-powerful machines.

The modern technological holy grail, the source of all science fiction fantasies, the quantum computer, is it on its way to becoming a reality? But above all: what is its computing power to be used for, and could it – as some scientists say – “make man as powerful as a god”?

A little story about science … and computers

Understanding what a quantum computer is requires knowing – even in a basic way – the history from which it came. That quantum physics is a discovery from the beginning of the 20th century. It is actually particle physics, of the infinitely small. Scientists of that time – around 1925 – discovered that the properties of atoms, their electrons and all particles on the scale of one billionth of a meter, are special: they do not follow the same rules as those in the macroscopic world. That quantum theory (modeling the behavior of energy on a very small scale), invented at the same time, thus gives name to this new physics.

It is thanks to these – strange and disturbing – properties of the “world of the infinitely small” that modern computers were able to create themselves. Microprocessors’ transistors are, for example, metal semiconductors that use the properties of quantum physics: materials that can pass an electric current or, conversely, prevent it from circulating, thus preserving type 1 or 0 binary information. The word “electronic” comes from electron …

But how does a classical computer differ from a quantum computer if it already uses the quantum properties of the materials in its components? The answer is complex, but can be summarized with this definition:

In a quantum computer, the logical gates that process information in the form of 1s and 0s (each computer bit is a value of 1 or 0 in a classical computer) are made of rather special atoms, ie. Rydberg atoms. These atoms have highly excited electrons, which orbit very far from the nucleus and are therefore very sensitive to electromagnetic fields.

In the infinitely small, where these interact Rydberg atoms – specific to quantum computers -, quantum laws mean that bits are then in a “superposition of states “between 1 and 0 and become entangled in each other: these are qubits do not bite. The qubits of quantum computers have a quantum state, which allows them to possess an “infinity of values”, in theory, but they are also very “fragile”, as they do not support contact with the macroscopic world. It is this physical limitation that makes it very difficult to build quantum computers.

Mathematician, computer scientist and physicist Julia Kemp defines a qubit as: “We call qubit these quantum bits, which are both in state 0 and in state 1. When we try to observe a qubit, we find either a 0 or a 1. But the observation has changed the state of the particle, choosing between the two.

Race for supremacy

Two years ago, at CES, the annual US technology fair, IBM unveiled the first “portable” quantum computer: the “IBM Q System One”. The machine is equipped with a 20-qubit calculator and is a glass cube that still takes up 20 m3, in which – in addition to the electronic components – there is a helium tank, liquid and cryogenic equipment that enables qubits to operate at a temperature close to .. absolutely zero (−273.15 ° C).

That same year, 2019, Google announced that it had reached “quantum domination,” in collaboration with NASA and the Oak Ridge National Laboratory (ORNL), thanks to a 54-qubit quantum computer called the “Sycamore.” der “quantum superiority“is a threshold from which the quantum computer becomes an operational technology capable of performing tasks that no conventional computer will ever be able to perform. Google’s announcement of the performance of its” Sycamore “- which would have performed a complex calculation in 200 seconds, while a non-quantum supercomputer would only do so in 10,000 years – has been challenged by IBM, which according to rival company Google, their conventional supercomputers would take 2 days to perform the calculation.

Disruptive technology

Despite sometimes imaginative or difficult to verify messages over time – by competing firms – the reality of quantum computers is now undeniable. Quantum algorithms – the first of which were created 30 years ago – are therefore used by these “retro-futuristic” machines, which are similar in size to computers from the 1960s.

Today, two main paths for technological development are thus maintained, as the “Quantique” report, which was presented to the French President in January 2020, states:

This results in two main types of quantum computers:

A “universal” quantum computer with significant power called “LSQ” for “Large Scale Quantum”, which would be composed of thousands of logical qubits and would have the ability to perform any kind of quantum calculation. This type of calculator would exponentially surpass today’s most powerful supercomputers for a large number of applications. The first “LSQ” calculators not expected until 2030.

A “noisy” quantum computer in medium size called “NISQ” for “Noisy Intermediate Scale Quantum”, which on the contrary would be composed of a few hundred physical qubits that allow a certain number of specific calculations to be performed. This type of calculator was born a few years ago in machines developed by IBM, Google and RIGETTI in particular with a few dozen qubits.

Emmanuel Macron announced on January 21 that nearly 800 million of the 1.8 billion of the “Quantum Plan” invested over 5 years would make it possible to “develop a hybrid computer, especially for chemistry, logistics, artificial intelligence by 2023In addition, € 320 million will be allocated to quantum communication systems, € 250 million for quantum sensors, € 150 million for post-quantum cryptography and € 290 million will be invested in quantum technology-related technologies (lasers, cryogenics).) The French head of state specified that if these first phases were to make it possible to develop quantum simulators and more specifically the hybrid computer, he would ultimately focus on the construction of a true universal quantum computer …

Quantum technologies: some examples of applications

That quantum technologies bring remarkable benefits in chemical and physical simulations with potential uses in agriculture, drug discovery and battery design ; that quantum algorithms enables dramatic speeds in optimization and machine learning applications, especially in the fields finance, energy, automotive and environmental sciences ; that quantum communication network able to improve the security of sensitive data in the long run. The researchers believe that this technology would make it possible discover new exoplanetsof create new climate models or even off design new drugs a few hours after starting a program.

Acceleration of computational speed in machine learning (artificial intelligence) thanks to quantum technologies – even hybrids – allows for better analysis and sorting of information in very large digital databases. The benefits would be several, such as improved internet search engines or much more accurate medical diagnoses. All these options should be framed, say specialists in the field, who called the American daily newspaper Wall Street JournalFebruary 1, 2021 to ethical rules on quantum calculation.

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