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In a small laboratory in a lush countryside a hundred kilometers north of New York, a complex mess of tubes and electronics hang from the ceiling. It's a computer, even if promiscuous. And this is not the most common computer. Perhaps his family is written to become one of the most important in history. Quantum computers promise to make calculations far beyond the reach of any conventional supercomputer. They can produce revolutions in the field of creating new materials, allowing to simulate the behavior of matter down to the atomic level. They can bring cryptography and computer security to a new level, hacking the impenetrable codes to this day. There is even a hope that they will bring artificial intelligence to a new level, help it to more effectively sift and process the data.
And only now, after decades of gradual progress, scientists finally approached the creation of quantum computers powerful enough to do what ordinary computers can not do. This landmark is beautifully called "quantum superiority." The move to this landmark is headed by Google, followed by Intel and Microsoft. Among them - well-financed start-ups: Rigetti Computing, IonQ, Quantum Circuits and others.
And yet no one can compare with IBM in this area. 50 years ago the company achieved success in the field of materials science, which laid the foundation for the computer revolution. So last October MIT Technology Review went to the Thomas Watson Research Center at IBM to answer the question: in what way will a quantum computer be good? Is it possible to build a practical, reliable quantum computer?
Why do we need a quantum computer?
This research center, located in Yorktown Heights, is a bit like a flying saucer, as it was intended in 1961. It was designed by Neo-Futurist architect Eero Saarinen and built during the heyday of IBM as the creator of large mainframe for business. IBM was the largest computer company in the world, and for ten years of construction of the research center it became the fifth largest company in the world, just after Ford and General Electric.
Although the corridors of the building look at the village, the design is such that in none of the offices inside there are windows. In one of these rooms, Charles Bennet was discovered. Now he is 70, he has big white whiskers, he wears black socks with sandals and even a pencil case with handles. Surrounded by old computer monitors, chemical models and, unexpectedly, a small disco ball, he recalled the birth of quantum computing as if it were yesterday.
When Bennett joined IBM in 1972, quantum physics was already half a century old, but the calculations still relied on classical physics and mathematical theory for information that Claude Shannon developed at MIT in the 1950s. It was Shannon who determined the amount of information by the number of "bits" (he popularized this term, but did not invent it) necessary for its storage. These bits, 0 and 1 binary code, formed the basis for traditional calculations.
A year after arriving at Yorktown Heights, Bennett helped lay the foundation for the theory of quantum information, which challenged the previous one. It uses the bizarre behavior of objects in atomic scales. On such a scale, a particle can exist in the "superposition" of a set of states (that is, in a set of positions) simultaneously. Two particles can also "become entangled", so that a change in the state of one instantly responds to the second one.
Bennett and others realized that some kinds of computations that take too much time or are not possible at all could be effectively carried out using quantum phenomena. A quantum computer stores information in quantum bits, or qubits. Qubits can exist in superpositions of ones and zeros (1 and 0), and confusion and interference can be used to find computational solutions in a huge number of states. Comparing quantum and classical computers is not entirely correct, but, figuratively speaking, a quantum computer with several hundred qubits can produce more calculations simultaneously than atoms in a known universe.
In the summer of 1981 IBM and MIT organized a landmark event called "The First Conference on Computational Physics". It was held in the hotel Endicott House, a mansion in the French style near the campus MIT.
In the photo that Bennett made during the conference, on the lawn, one can see some of the most influential figures in the history of computing and quantum physics, including Conrad Zuse, who developed the first programmable computer, and Richard Feynman, who made an important contribution to quantum theory. Feynman held a key speech at the conference, in which he raised the idea of using quantum effects for computations.
The biggest push quantum theory of information received from Feynman, "says Bennett. "He said: the nature of quantum, her mother! If we want to imitate it, we need a quantum computer. "
A quantum computer IBM - one of the most promising of all existing - is located right along the corridor from Bennett's office. This machine is designed to create and manipulate an important element of a quantum computer: the qubits that store information.
The gap between dream and reality
The IBM machine uses quantum phenomena that occur in superconducting materials. For example, sometimes the current flows clockwise and counterclockwise simultaneously. The IBM computer uses superconducting chips, in which two different electromagnetic energy states are qubit.
The superconducting approach has many advantages. Hardware can be created using well-known established methods, and you can use a regular computer to manage the system. The qubits in the superconducting scheme are easily manipulated and less delicate than individual photons or ions.
In the IBM quantum laboratory, engineers are working on a version of a computer with 50 qubits. You can run a simulator of a simple quantum computer on an ordinary computer, but with 50 qubits it will be almost impossible. And this means that IBM theoretically approaches the point at which a quantum computer can solve problems that are not accessible to a classic computer: in other words, quantum superiority.
But IBM scientists will tell you that quantum superiority is an elusive concept. You will need all 50 qubits to work perfectly when in reality quantum computers suffer greatly from errors. It is also incredibly difficult to maintain qubits for a given period of time; they tend to "decoherence", that is, to the loss of their delicate quantum nature, like a ring of smoke dissolves at the slightest blow of the breeze. And the more qubits, the more difficult it is to cope with both tasks.
"If you had 50 or 100 qubits and they really worked well enough, and were completely free of errors, you could produce incomprehensible calculations that could not be reproduced on any classic machine, neither now nor then, nor in the future, "says Robert Shelkopf, a professor at Yale University and founder of Quantum Circuits. "The reverse side of quantum computing lies in the fact that there is an incredible number of opportunities for error."
Another reason for caution is that it is not entirely clear how useful even an ideally functioning quantum computer will be. It does not just speed up the solution of any task that you throw to it. In fact, in many kinds of calculations it will be incommensurably "dumber" than classical machines. Not many algorithms have been determined to date, in which a quantum computer will have an obvious advantage. And even with them, this advantage can be short-lived. The most famous quantum algorithm, developed by Peter Shore from MIT, is designed to search for simple integer multipliers. Many well-known cryptographic schemes rely on the fact that this search is extremely difficult to implement a conventional computer. But cryptography can adapt and create new types of code that do not rely on factoring.
That's why, even when approaching a 50-kilobit milestone, IBM researchers themselves are trying to dispel the hype. At the table in the corridor, which overlooks a lush lawn outside, stands Jay Gambetta, a tall Australian exploring quantum algorithms and potential applications for IBM equipment. "We are in a unique position," he says, carefully choosing the words. "We have this device, which is the hardest that can be modeled on a classic computer, but it is not yet controlled with sufficient accuracy to conduct known algorithms through it."
What gives all aybiemshchikam hope that even an imperfect quantum computer can be useful.
Gambetta and other researchers began with an appendix that Feynman had foreseen back in 1981. Chemical reactions and material properties are determined by interactions between atoms and molecules. These interactions are governed by quantum phenomena. A quantum computer can (at least in theory) model them in a way that ordinary can not.
Last year, Gambetta and his IBM colleagues used a seven-kilobit machine to model the exact structure of beryllium hydride. Consisting of only three atoms, this molecule is the most complex of all, which were modeled using a quantum system. Ultimately, scientists will be able to use quantum computers to design efficient solar cells, drugs or catalysts that convert sunlight into clean fuel.
These goals, of course, are still unimaginably far off. But as Gambetta says, valuable results can be obtained already from working in a pair of quantum and classical computers.
What for a dream physicist, for an engineer a nightmare
"The sensation is pushed by the realization that quantum computing is real," says Isaac Chuan, a professor at MIT. "It's not a dream physicist - it's an engineer's nightmare."
Chuan led the development of the very first quantum computers, working at IBM in Almaden, California, in the late 1990s and early 2000s. Although he no longer works for them, he also believes that we are at the beginning of something very large and that quantum computing will ultimately play a role even in the development of artificial intelligence.
He also suspects that the revolution will not begin until a new generation of students and hackers begin to play with practical machines. Quantum computers require not only other programming languages, but also a fundamentally different way of thinking about programming. As Gambetta says, "we really do not know what is equivalent to" Hello world "on a quantum computer."
But we begin to look. In 2016 IBM connected a small quantum computer with a cloud. Using the QISKit programming tool, you can run simple programs; thousands of people, from academics to schoolchildren, have already created programs on QISKit that process simple quantum algorithms. Now Google and other companies are also trying to bring quantum computers online. They are not capable of much, but they give people the opportunity to experience what quantum computing is.
The article is based on materials .
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