The first quantum circuit lays the foundation for a computer revolution

This first quantum integrated circuit at the atomic scale represents an important step in the development of quantum computation that is useful under real conditions.

Australian researchers have just announced the creation of what they describe as “first quantum integrated circuit manufactured on an atomic scalein fact, they confirm that all the elements necessary for the operation of a computer of this type have been successfully mounted on a standard format chip.

And this circuit is even capable of functioning as a full-fledged quantum processor. It made it possible for scientists to simulate the motion of electrons in a small molecule, polyacetylene. It has the advantage that it is perfectly known by scientists. The latter can therefore immediately determine the consistency of the result, and by extension the reliability of the chip.

And at the end of the test protocol, the result was clear: The circuit showed astonishing precision during the simulations. According to researchers, this is enough to “definitively prove the validity of this technology in the context of quantum modeling systems”.

This work published in the prestigious journal Nature is very exciting. It is truly a proof of concept that undoubtedly brings us closer to the democratization of quantum computers, even though this deadline is still far away.

From simple “transistor” to real circuit

This cycle is the very first manifestation of a long series of works that started in 2012. At that time, quantum computation was even more in its infancy than it is today. These same scientists had just created the very first “quantum transistor”.

Transistors are small electronic components based on semiconductor materials – those whose deficiency has set technology on fire for several months. In short, they function as small 100% electronic contacts; they are therefore fundamental elements in all logic circuits as they support the famous “bits”.

It is therefore an eminently important technological base for all modern computer. This is a technology that is now very well mastered and the manufacturers are making real feats when it comes to miniaturizing these components. But that’s a different story when it comes to applying this concept to quantum computation, where everything is played out on the scale of the infinitely small.

Humans already master the production of microscopic components very well … © Umberto – Unsplash

An extremely demanding manufacturing process

To build their chip, they had to use a transmission electron microscope that was able to distinguish details on an atomic scale. They then had to perform the whole process in almost absolute vacuum, because on this scale even a single oxygen atom could be a problem.

These are very important limitations which it is unfortunately impossible to circumvent in order to achieve the desired level of precision on the final chip. This allowed researchers to arrange a host of quantum dots, better known as quantum dots (QDs). A name that will definitely ring a bell for fans of screen technology.

Specifically, these QDs are structures based on semiconductor materials, such as the transistors of current computers. On the other hand, these measure only a few nanometers. They can therefore behave like quantum transistors once arranged with extreme precision. They can therefore act as pixels in some high-end OLED screens. Just as standard transistors house bits, these quantum dots can also serve as carriers for qubits, the basic unit of quantum computation.

But on this scale, tolerances are largely non-existent. The researchers had to determine the exact number of phosphorus atoms needed in each QD. They should then determine the position of each point and then arrange them on the chip with a precision well below a nanometer and a margin of error close to zero.

If they are too large or too dense, the interactions between the points become too strong; it becomes impossible to control them individually. Conversely, if they are too small or too far apart, these interactions become unpredictable. In either case, it impairs the function of the chip.

… But everything becomes more complicated when working on the scale of elementary particles. © Norbert Kowalczyk

The beginning of a real paradigm shift?

Not surprisingly, therefore, the researchers needed very many iterations to build their chip; they managed to place 10 QDs there. This therefore represents a major effort for a circuit which ultimately remains weak despite its precision. In fact, these 10 qubits are still insufficient to be useful under real conditions.

But the interest in this work lies more in the method than in the final product. By opening the door to the production of real quantum chips, we can begin to get a glimpse of the first practical and relatively “mainstream” applications (all things considered) of this technology.

For at present the practical interest in these machines is still very limited; they are mainly exploration tools that are not really used to perform concrete work. In addition, quantum computers are currently reserved for institutions that have significant technological and financial resources.

In the end, chips of this kind might serve as a vector to break this exclusivity and democratize quantum computers. The obstacles are still numerous; to start, it would already be necessary to produce a circuit much more powerfuland able to operate at room temperature.

Technically, IBM’s Q System One is the first circuit-based quantum computer; but his chip was not yet self-sufficient, contrary to the Australian researchers’ proof of concept. © IBM Research

To work, current quantum computers must be kept at a temperature close to absolute zero. The challenge, therefore, is to find a way to overcome this limitation; but at present no one has yet found the slightest trace in this direction. And this is just an isolated example among a mountain of borders (see our articles here, here and here) it still inhibits the development of quantum computers.

It is therefore not tomorrow that this technology will become the norm. But it is undeniably an important step in this direction. In traditional data processing, the first transistor appeared in 1947the first integrated circuit in 1958and the first personal computers in the years 1970. If quantum computing follows a comparable trajectory (which is anything but a guarantee), the long-awaited computer revolution may well come. within a few decades.

The text of the study is available here.

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