Trying to overcome the noise in a quantum computer

artificial intelligence? Creating alternate universes? In the research laboratory of Dr. Roi, my assistants at the Weizmann Institute of Science do not sail into the hair-raising consequences conceived by science fiction writers. They prefer to focus on a specific question: the preservation of the information encoded in the atom

At the end you see metal cylinders, flashes of laser beams in different colors, you see a field of upright lenses. At the end, you see a tube inside of which, in the heart of electric fields, an atom is trapped, one of whose electrons has been torn off, cooled almost to absolute zero temperature. To me, this is the miracle of technology, the ability to embody the great theories in sixty objects, in boxes that change the world. Because the atom lying motionless in the research laboratory of Dr. Roi Ozeri can, indirectly, help build an efficient quantum computer.

The basic lines of quantum computing were already laid down in the 80s, and they are derived from a feature that particles exhibit at the quantum level - being in several physical states at the same time. The most famous example of this is Schrödinger's cat: a cat is in a closed box, where there is also a capsule of poisonous gas with a sensitive switch responsible for releasing its contents. shoot an electron at the switch. Is the cat alive or dead? Well, as long as you don't open to check, the cat exists in two realities, in one he was poisoned and died, and in the other he is alive and breathing, because the electron, being its position in space is a probability function and not a fixed point, hit the switch and didn't hit either. This exact superposition can be used to process information.

Today's digital computers, however sophisticated they may be, are built on a binary principle. The bits that perform the data processing can be in one of two states, one or zero. Quantum bits - that is, elementary particles that one of their properties represents information - can be in several states at the same time. What makes it possible, theoretically, to process huge amounts of information: while a digital computer will serially run possible solutions to a particular problem, a quantum computer will run them all at the same time. The implications of a technology that will succeed in harnessing this processing power span between the immediate and the unimaginable.

The direct consequences, unfortunately, are the source of funding for most research in the field of quantum computing. One of the main purposes of the first quantum computer will be to run an algorithm to find the prime factors of a given number, a task that is considered impossible to perform in a time that is not a generation, and therefore constitutes the working assumption of digital information encryption today. The owner of a quantum computer - and it is assumed that due to the production costs and the required knowledge it will be a government institution or a powerful body - will have free access to every piece of information that rushes to the virtual spaces, on its way to the Internet. But Dr. Ozari and his team of experimental physicists - Nitzan Akerman, Yanon Glickman, Anna Kesselman, Yonatan Dalal and Shlomi Kotler - in their laboratory in the Department of Physics of Complex Systems at the Weizmann Institute of Science, are not interested in the immediate consequences or even the hair-raising ones conceived by science fiction writers in recent decades - Artificial intelligence (is the human brain a quantum computer?), or the creation of alternate universes. No. They want to check how the information already encoded in the superposition of the frozen atom at the heart of the electric fields can be preserved.

Because quantum computing technology has two weak points: the first - as soon as a measurement is made, as soon as Schrödinger's box is opened to check the state of the cat, the possible realities of the particle disappear, leaving only one reality; And the second - as soon as you increase the number of quantum bits, or particles, noise is created, the information begins to flow and disappear, some states disappear.

The two points involve each other. In fact, this is the common explanation for why, in our everyday experience, objects do not behave in warped quantum ways, flickering on the brink of existence according to their probability of appearing. Dr. Ozari says: "It is impossible to point to an obstacle. If the system is the sum of all its parts, there is no reason why, under the right conditions, an object in our world would not behave in a quantum manner." and wants to put the claim to the test by creating protocols to prevent the disappearance of information in complicated quantum systems, that is, systems that count several particles. Methods to prevent the disappearance or corruption of information are already implemented in any information encoding, whether on CDs or hard disks. To find methods that will be effective in complex quantum systems, Dr. Ozari and his team engineer unconventional information leaks and track how they occur. The next step will be to find ways to defend against them, that is, to make complicated quantum systems preserve the relevant information, despite the measurements that are carried out in them, despite their size. If they get their way, then the end of the days of the information age will be one step closer, or we will, as Dr. Ozari hopes, in a metaphorical way, see Schrödinger's cat live and die at the exact same moment.

More about the research of Dr. My assistants and his team