2024-07-02 08:34:55
By Maria Benito (CSIC)*
Imagine having a computer capable of doing calculations at stratospheric speed. Or to solve immediate problems that a ‘normal’ computer would take the same age of the world to solve. Sounds interesting, isn’t it?
Him quantum computer promises to make all this possible by replacing the ‘ordinary’ pieces, the basic units of information or ‘bricks’ on which traditional computers operate, with ‘magic’. a cubit (of English:’qubit‘). Unlike bits, which can only take the values 1 or 0, qubits can simultaneously exist in a hierarchy of states or bind… And that will allow very complex calculations to be done immediately and efficiently .
And why don’t we already have quantum computers in our homes? Well, because, although they have been working for more than 20 years to make them a reality, their bricks are more fragile than traditional ones. You’ve probably dropped your phone on the floor at some point, but when you pick it up, you’re happy to see that it’s still working normally. Sorry to say that Today’s quantum computers are much more fragile…
Obsessed with noise
There are different types of qubits. At the Institute of Microelectronics of Barcelona (IMB-CNM, CSIC), we do superconducting qubits. In order for them to have this property, superconductivity, they must be cooled below their temperature: 1.2 degrees Kelvin in the case of aluminum.
The shiny gold chandeliers you see in the picture fulfill this function: they keep many floors or levels at descending temperatures: 4 degree Kelvin, 1 degree Kelvin… up to 0.02 degrees Kelvin! To give you an idea, the vacuum of outer space has the lowest temperature: 0 degrees Kelvin, or -273.15 degrees Celsius, a state characterized by a lack of energy.
There are those who work on quantum computers we are obsessed with reaching these very low temperatures, which requires warm attention from the outside. WE HAD including ‘shielding’ these computers to prevent any other form of interference, or what is considered noise: Cosmic radiation, nuclear radiation, photons, magnetic fields…
And you will think: “What paranoids…”. Maybe, but there is an explanation.
In these chandeliers there may be thousands of qubits performing continuous operations. And, unfortunately, it often happens that These qubits undergo a phenomenon called ‘decoherence’, whereby they lose their quantum state. In other words: what makes them something ‘magical’, systems capable of being at the top of states, completely disappear.
Without going into too much detail, all these noise sources accelerate, through different mechanisms, the characterization of superconducting qubits. Therefore, we seek to reduce them as much as possible to have as many homogeneous qubits as possible.
Quality qubits
He has tried to insulate with materials that do not allow the magnetic field to penetrate to build these computers underground to stop cosmic radiation. But they fail… Could the answer lie within the cage itself? That is, can we improve the progress quality qubit from its constituent materials?
“You can paint your house with the best color if the base is not good, you will not have the best result.” This statement can help us to illustrate what happens in a computer: “You can use thousands of algorithms to avoid convergence, but if the qubit is not good, you will not achieve the computing power you need.”
Therefore, at IMB-CNM we work to find the best recipe to produce qubits that resist or reduce decay..
Our superconducting qubits They are made up of a chip that includes a pair of ‘Josephson junctions’. The chip is made of a substrate and a thin layer of aluminum or other organic material. Josephson traces are also two layers of aluminum or other organic material separated by an insulator, which may be aluminum oxide itself.
To find the qubit we are looking for, we use different substrates (the ‘base’ of the integrated circuit) or change the embedded device. It’s not easy, because something as ‘stupid’ as the type of cleaning you do beforehand, or the seconds it takes at each stage of the process, is decisive for the final result. So, we have to work on it White room, a highly controlled environment that works to reduce the number of polluting particles. Each revision is a challenge, but also a fun experience.
Will we be able to achieve it? It’s hard to predict, but if people manage to build tall buildings using reinforced concrete instead of wood, one day we’ll be able to make better computational bricks.
* Maria Benito He is a predoctoral researcher at CSIC at the Barcelona Institute of Microelectronics (IMB-CNM).
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