Russian and American scientists from Harvard University, working in the group of Mikhail Lukin, have created a quantum computer of 51 qubits, the most powerful in the world today. This was stated by the co-founder of the Russian Quantum Center (RCC), Professor Lukin, in his report at International Conference on Quantum Technologies (ICQT-2017), which was held in July in Moscow under the auspices of the RCC.
Unlike classical digital computers, whose memory is built on the principle of a binary code (0 or 1, "yes" or "no"), quantum computers are built on the basis of qubits - quantum bits. They also allow two states (0 and 1), but due to its quantum properties, a qubit additionally allows superposition states, that is, conditionally speaking, a lot of intermediate states between the two main states, described by complex (imaginary) numbers. It is clear that under such conditions the power and speed of a quantum computer are several orders of magnitude higher.
The very idea of using quantum computing to solve purely math problems proposed back in 1980 by Yuri Manin from the Steklov Institute, and a year later, the principle of building a quantum computer was formulated by Richard Feynman. But decades passed before the technologies appeared that could put their ideas into practice.
The main problem was to create stable working qubits. Lukin's group used for them not superconductors, but so-called cold atoms, which are kept inside laser traps at ultra-low temperatures. This allowed the physicists to create the world's largest 51-qubit quantum computer and outperform their colleagues at the University of Maryland's Christopher Monroe group (5-qubit device) and John Martinis' group at Google (22-qubit device).
Figuratively speaking, during the construction of a qubit computer, physicists returned from digital to analog devices of the first half of the last century. Now their task is to move to the "digit" at a new, quantum level. Using a set of qubits based on "cold atoms", Lukin's team has already been able to solve several specific physical problems that are extremely difficult to model using classical computers.
In the near future, scientists intend to continue experiments with a quantum computer. In addition to solving purely scientific tasks from the area quantum mechanics Professor Lukin does not rule out that his team will try to implement on it the famous Shor quantum algorithm, which is beyond the power of the current encryption systems. But there are many other practical areas where a new generation of computers could revolutionize. For example, hydrometeorology, where the power of existing computing devices is clearly not enough to improve the accuracy of weather forecasts.
Quantum computers are taking their first steps, but the time is not far off when they will become as common as today's PCs.
Phystech graduate Mikhail Lukin set up an experiment that amazed the world
M. Lukin entered the Moscow Institute of Physics and Technology in 1988 at the FFKE, basic training passed at the Department of Solid State Electronics under the guidance of Academician Yu. V. Gulyaev. He was engaged in scientific work under the guidance of V. I. Manko, A. F. Popkov, I. A. Ignatiev. After the 4th course, he was sent for 9 months to the University of Alabama (USA). Upon his return, he defended his thesis and ahead of schedule, in 1993, graduated from the Moscow Institute of Physics and Technology with honors. On the recommendation of Professor V. I. Manko, he was invited to the University of Texas to Professor M. Scully, in 1998 he defended his thesis. per cycle scientific works in 1999 he was awarded the medal of the American Optical Society.
What has our Lukin done? HE STOP THE BEAM OF LIGHT!
(from an exclusive interview with the correspondent of "KP" A. Kabannikov with a Russian scientist)
- ... How did you end up in America?
I was invited to graduate school at the University of Texas. And after defending his thesis on the use of lasers to control the environment, he received a special scholarship from Harvard for research.
- Where did the idea of the light delay experiment come from?
Two years ago, my former head of the University of Texas, Marlon Scully, turned 60 years old. On this occasion, it is customary to issue anniversary collections with the work of students. We have been thinking about the topic for a long time. At that time there was a lot of talk about slow light - the deceleration of its impulses. Literally three days before the submission of the manuscript, I and two young colleagues from Germany - Susanna Yelin and Mike Fleischhauer - finally decided that we would write about how to stop the light and use it as a way to save information.
Approximately a year was spent on theoretical justifications. The experiments began in April and by the fall had the first results, which fully confirmed the theory.
The most fantastic descriptions of your work are heard in the press. It is argued, for example, that the experiment refutes the theory of relativity. They even say that you can stop time in about the same way ...
This is the speculation of sensation lovers. What actually happened? Imagine an ordinary beam directed at some object. A pulse of light interacts with atoms, they are excited, radiate energy. Then it is lost - in the form of heat, glow. We have prepared a special environment of supercooled rubidium vapor. And then, with the help of a control laser, they made it electromagnetically conductive. A pulse of light was directed at her. When it reached Wednesday, we turned off the control laser. The momentum slowed down to zero, there were no photons. But the information was preserved inside the excited medium. And if you turn on the control laser again, the same pulse will continue its movement at the same speed. That, in fact, is all.
The New York Times covered your experiment on the front page, followed by the press all over the world reporting it as a scientific sensation with a great future...
Do not convict me of false modesty, but in fact the significance of the work is inflated. Made a small step in a small area. Although the implementation of the idea in its full form is fraught with interesting potential and can bring great results.
Do scientific commentators believe that your experience marks a step towards a revolution in computer technology?
This is more of a matter for engineers, and we are engaged in pure science. But experience points to fundamentally new possibilities for storing and processing information. Although the path to them from laboratory experience huge, it will take years and even decades.
Somehow, this experiment brought you fame in the scientific world; at the age of 29 you are five minutes away a professor at the University of Cambridge. Is there merit in this? Russian school?
Without any doubt! MIPT has been and remains a first-class university. A number of methods used by us are based on the ideas and developments of Professor Vladlen Letokhov from the Institute of Spectroscopy Russian Academy Sciences. When two Americans and a Frenchman received the Nobel Prize for laser cooling two years ago, many believed that Letokhov should have been among the winners. Almost all the knowledge about the approaches to the experiment I got by collaborating with a group of remarkable scientists of the Lebedev Physical Institute.
And is it not a paradox at the same time that the experiment that surprised the world according to Russian methods was staged by Russian scientists ... in America?
impoverished domestic science Today it rests only on veterans of the old school... I really assess the situation: believe me, if MIPT had the funds for research, they would have coped with the same task in just two years.
Washington.
Physical Review Letters
January 29, 2001 - Volume 86, Issue 5, pp. 783-786
Full Text: PDF (163 kB)
Storage of Light in Atomic Vapor
D. F. Phillips, A. Fleischhauer, A. Mair, and R. L. Walsworth Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138
M. D. Lukin ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138
We report an experiment in which a light pulse is effectively decelerated and trapped in a vapor of Rb atoms, stored for a controlled period of time, and then released on demand. We accomplish this "storage of light" by dynamically reducing the group velocity of the light pulse to zero, so that the coherent excitation of the light is reversibly mapped into a Zeeman (spin) coherence of the Rb vapor. ©2001 The American Physical Society
URL: http://publish.aps.org/abstract/PRL/v86/p783
DOI: 10.1103/PhysRevLett.86.783
PACS: 42.50.Gy, 03.67.-a Additional Information
References
1. M. D. Lukin, S. F. Yelin, and M. Fleischhauer, Phys. Rev. Lett. 84, 4232 (2000); L. M. Duan, J. I. Cirac, and P. Zoller (unpublished).
2. M. Fleischhauer and M. D. Lukin, Phys. Rev. Lett. 84, 5094 (2000).
3. L. V. Hau, S. E. Harris, Z. Dutton, and C. H. Behroozi, Nature (London) 397, 594 (1999); M. Kash et al., Phys. Rev. Lett. 82, 5229 (1999); D. Budker et al., ibid. 83, 1767 (1999).
4. See, e.g., S. E. Harris, Phys. Today 50, no. 7, 36 (1997).
5. Dissipative techniques for the partial transfer of quantum statistics from light to atoms are reported in A. Kuzmich, K. Mölmer, and E. S. Polzik, Phys. Rev. Lett. 79, 4782 (1997); J. Hald, J. L. Schrensen, C. Schori, and E. S. Polzik, Phys. Rev. Lett. 83, 1319 (1999).
6. J. I. Cirac, P. Zoller, H. J. Kimble, and H. Mabuchi, Phys. Rev. Lett. 78, 3221 (1997).
7. M. Hennrich, T. Legero, A. Kuhn, and G. Rempe, Phys. Rev. Lett. 85, 4872 (2000).
8. M. D. Lukin et al., quant-ph/0011028.
9. L. Duan, J. I. Cirac, P. Zoller, and E. Polzik, quant-ph/0003111.
10. A. Kuzmich, L. Mandel, and N. Bigelow, Phys. Rev. Lett. 85, 1594 (2000).
11. O. Kocharovskaya, Yu. Rostovtsev, and M. O. Scully, Phys. Rev. Lett. 86, 628 (2001).
12. H. Schmidt and A. Imamolu, Opt. Lett. 21, 1936 (1996); ; S. E. Harris and Y. Yamamoto, Phys. Rev. Lett. 81, 3611 (1998); S. E. Harris and L. V. Hau, ibid. 82, 4611 (1999); M. D. Lukin and A. Imamolu, ibid. 84, 1419 (2000).
13. For observation of Zeeman-coherence-based EIT in a dense medium, see V. A. Sautenkov et al., Phys. Rev. A 62, 023810 (2000).
14. In our present experiment up to ~50% of the input light excitation has been trapped. We anticipate that the stored fraction can be increased by either using a larger density-length product or with an optical cavity .
15 S. E. Harris, Phys. Rev. Lett. 70, 552 (1993); M. D. Lukin et al., Phys. Rev. Lett. 79, 2959 (1997).
16.C. Liu, Z. Dutton, C. H. Behroozi, and L. V. Hau, Nature (London) (to be published).
Russian and American scientists working at Harvard have created and tested the world's first 51-qubit quantum computer, the most complex computing system of its kind.
This was stated by Professor of Harvard University, co-founder of the Russian Quantum Center (RQC) Mikhail Lukin, RIA Novosti reported.
The physicist spoke about this at the International Conference on Quantum Technologies ICQT-2017 in Moscow.
This achievement allowed Lukin's group to become a leader in the "race" to create a full-fledged quantum computer, which has been unofficially going on for several years between several groups of the world's leading physicists.
Quantum computers are special computing devices whose power grows exponentially due to the use of the laws of quantum mechanics in their work.
All such devices consist of qubits - memory cells and at the same time primitive computing modules capable of storing a range of values between zero and one.
Today, there are two main approaches to the development of such devices - classical and adiabatic.
Supporters of the first of them are trying to create a universal quantum computer, the qubits in which would obey the rules by which conventional digital devices operate.
Working with such a computing device ideally will not be much different from how engineers and programmers manage conventional computers.
An adiabatic computer is easier to build, but closer in principle to the analog computers of the early 20th century than to the digital devices of today.
Last year, several teams of scientists and engineers from the United States, Australia and several European countries announced that they were close to creating such a machine.
The leader in this informal race was the team of John Martinis from Google, which is developing an unusual "hybrid" version of a universal quantum computer that combines elements of the analog and digital approaches to such calculations.
Lukin and his colleagues at the RCC and Harvard have bypassed the Martinis group, which is now working on a 22-qubit computer, using not superconductors, like scientists from Google, but exotic "cold atoms".
As Russian and American scientists have discovered, a set of atoms held inside special laser "cages" and cooled to ultra-low temperatures can be used as quantum computer qubits that remain stable under a fairly wide range of conditions. This allowed physicists to create the largest quantum computer of 51 qubits so far.
Using a set of similar qubits, Lukin's team has already solved several physics problems that are extremely difficult to model using "classical" supercomputers.
For example, Russian and American scientists were able to calculate how a large cloud of interconnected particles behaves, to detect previously unknown effects that occur inside it. It turned out that when the excitation is damped, certain types of oscillations can remain and remain in the system indefinitely, which scientists were not aware of before.
To verify the results of these calculations, Lukin and his colleagues had to develop a special algorithm that made it possible to carry out similar calculations in a very rough form on conventional computers. The results were broadly consistent, confirming that the Harvard scientists' 51-qubit system works in practice.
In the near future, scientists intend to continue experiments with a quantum computer. Lukin does not rule out that his team will try to run the famous Shor quantum algorithm on it, which allows you to break most existing encryption systems based on the RSA algorithm.
According to Lukin, an article with the first results of a quantum computer has already been accepted for publication in one of the peer-reviewed scientific journals.
The costs of the Russkoye Pole project are partially covered by funds provided by the Russkiy Mir Foundation
When it comes to outstanding Russian scientists, many remember the heroes of the past - Mendeleev, Pavlov or Landau, forgetting that among our contemporaries there are many outstanding researchers. By Day Russian science"Attic" has collected the names of those who made significant discoveries already in the 21st century.
Physics
Andrew Game. Photo: ITAR-TASS / Stanislav Krasilnikov
In the new millennium Nobel Prize in physics went to Russian-speaking scientists three times, though only in 2010 - for a discovery made in the 21st century. MIPT graduates Andrey Game And Konstantin Novoselov In the laboratory of the University of Manchester, for the first time, they were able to obtain a stable two-dimensional carbon crystal - graphene. It is a very thin - one atom thick - carbon film, which, due to its structure, has many interesting properties: excellent conductivity, transparency, flexibility, and very high strength. For graphene, new and new areas of application are constantly being found, for example, in microelectronics: flexible displays, electrodes, and solar panels are created from it.
Mikhail Lukin. Photo: ITAR-TASS / Denis Vyshinsky
Another graduate of the Moscow Institute of Physics and Technology, and now a professor of physics at Harvard University Mikhail Lukin , did the seemingly impossible: he stopped the light. For this, the scientist used supercooled rubidium vapor and two lasers: the control one made the medium conductive for light, and the second served as a source of a short light pulse. When the control laser was turned off, the particles of the light pulse stopped leaving the medium, as if stopping in it. This experiment was a real breakthrough in the creation of quantum computers - machines of a completely new type that can simultaneously perform an enormous number of operations. The scientist continued research in this area, and in 2012 his group at Harvard created the longest-lived qubit at that time, the smallest element for storing information in a quantum computer. And in 2013, Lukin for the first time received photon matter - a kind of substance, only consisting not of atoms, but of particles of light, photons. It is also planned to be used for quantum computing.
Yuri Oganesyan (center) with Georgy Flerov and Konstantin Petrzhak. Photo from the JINR electronic archive
Russian scientists in the 21st century have significantly expanded the periodic table. For example, in January 2016, elements with numbers 113, 115, 117 and 118 were added to it, three of which were first obtained at the Joint Institute for Nuclear Research (JINR) in Dubna under the guidance of Academician of the Russian Academy of Sciences Yuri Oganesyan . He also has the honor of discovering a number of other superheavy elements and the reactions of their synthesis: elements heavier than uranium do not exist in nature - they are too unstable, so they are created artificially in accelerators. In addition, Oganesyan experimentally confirmed that there is a so-called "island of stability" for superheavy elements. All these elements decay very quickly, but first theoretically, and then experimentally, it was shown that among them there should be those whose lifetime significantly exceeds the lifetime of their neighbors in the table.
Chemistry
Artem Oganov. Photo from personal archive
Chemist Artem Oganov , head of laboratories in the US, China and Russia, and now also a professor at the Skolkovo Institute of Science and Technology, has created an algorithm that allows a computer to search for substances with predetermined properties, even impossible from the point of view of classical chemistry. The method developed by Oganov formed the basis of the USPEX program (which reads as Russian word"success"), which is widely used around the world ("Attic" in detail). With its help, new magnets were discovered, and substances that can exist in extreme conditions e.g. under high pressure. It is assumed that such conditions may well exist on other planets, which means that the substances predicted by Oganov are there.
Valery Fokin. Biopharmaceutical cluster "Severny"
However, it is necessary not only to simulate substances with predetermined properties, but also to create them in practice. To do this, a new paradigm was introduced in chemistry in 1997, the so-called click chemistry. The word “click” imitates the sound of a latch, because a new term was introduced for reactions that must, under any conditions, combine small constituents into the desired molecule. At first, scientists were skeptical about the existence of a miracle reaction, but in 2002 Valery Fokin , a graduate of the Nizhny Novgorod state university named after Lobachevsky, now working at the Scripps Institute in California, discovered such a "molecular latch": it consists of azide and alkyne and works in the presence of copper in water with ascorbic acid. With the help of this simple reaction, completely different compounds can be combined with each other: proteins, dyes, inorganic molecules. Such a "click" synthesis of substances with previously known properties is primarily necessary for the creation of new drugs.
Biology
Evgeny Kunin. Photo from the personal archive of the scientist
However, in order to treat a disease, it is sometimes necessary not only to neutralize a virus or bacterium, but also to correct one's own genes. No, this is not a plot for a science fiction movie: scientists have already developed several "molecular scissors" systems capable of editing the genome (more on the amazing technology in the Attic article). The most promising among them is the CRISPR/Cas9 system, which is based on the mechanism of protection against viruses that exists in bacteria and archaea. One of the key researchers of this system is our former compatriot Evgeny Kunin , who has been with the US National Center for Biotechnology Information for many years. In addition to CRISPR systems, the scientist is interested in many issues of genetics, evolutionary and computational biology, so it is not for nothing that his Hirsch index (citation index of a scientist’s articles, reflecting how much his research is in demand) has exceeded 130 - this is an absolute record among all Russian-speaking scientists.
Vyacheslav Epshtein. Photo by Northwestern University
However, the danger today is provided not only by the breakdown of the genome, but also by the most common microbes. The fact is that over the past 30 years not a single new type of antibiotics has been created, and bacteria are gradually becoming immune to old ones. Fortunately for mankind, in January 2015, a group of scientists from the US Northeastern University announced the creation of a completely new antimicrobial agent. To do this, scientists turned to the study of soil bacteria, which had previously been considered impossible to grow in the laboratory. To get around this barrier, an employee of Northeastern University, a graduate of Moscow State University Vyacheslav Epshtein Together with a colleague, he developed a special chip for growing recalcitrant bacteria right on the ocean floor - in such a cunning way, the scientist circumvented the problem of increased "capriciousness" of bacteria that did not want to grow in a Petri dish. This technique formed the basis of a large study, which resulted in the antibiotic teixobactin, which can cope with both tuberculosis and Staphylococcus aureus.
Mathematics
Grigory Perelman. Photo: George M. Bergman - Mathematisches Institut Oberwolfach (MFO)
Even people who are very far from science have probably heard about mathematics from St. Petersburg Grigory Perelman . In 2002-2003 he published three papers proving the Poincaré conjecture. This hypothesis belongs to the branch of mathematics called topology and explains the most general properties space. In 2006, the proof was accepted by the mathematical community, and the Poincaré conjecture thus became the first one among the so-called seven millennium problems to be solved. These include classical mathematical problems whose proofs have not been found for many years. For his proof, Perelman was awarded the Fields Prize, often referred to as the Nobel Prize for mathematicians, as well as the prize established by Mathematical Institute Clay for solving the Millennium Challenges. The scientist refused all awards, which attracted the attention of the public far from mathematics.
Stanislav Smirnov. Photo: ITAR-TASS / Yuri Belinsky
Working at the University of Geneva Stanislav Smirnov in 2010 he also won the Fields Medal. The most prestigious award in the mathematical world was brought to him by the proof of the conformal invariance of two-dimensional percolation and the Ising model in statistical physics- this thing with an unpronounceable name is used by theorists to describe the magnetization of a material and is used in the development of quantum computers.
Andrey Okunkov. Photo: Radio Liberty
Perelman and Smirnov are representatives of the Leningrad School of Mathematics, graduates of the notorious School No. 239 and the Faculty of Mathematics and Mechanics of St. Petersburg State University. But there were also Muscovites among the nominees for the mathematical Nobel Prize, for example, a professor at Columbia University who worked in the United States for many years, a graduate of Moscow State University Andrey Okounkov . He received the Fields Medal in 2006, at the same time as Perelman, for achievements connecting probability theory, representation theory, and algebraic geometry. In practice, Okounkov's work different years have found applications both in statistical physics for describing the surfaces of crystals and in string theory, a field of physics that attempts to combine the principles of quantum mechanics and relativity theory.
Story
Petr Turchin. Photo: University of Technology Stevens
A new theory at the intersection of mathematics and humanities offered Petr Turchin . Surprisingly, Turchin himself is neither a mathematician nor a historian: he is a biologist who studied at Moscow State University and now works at the University of Connecticut and studies populations. Processes population biology develop over a long period of time, and for their description and analysis it is often necessary to build mathematical models. But modeling can also be used to better understand social and historical phenomena in human society. This is exactly what Turchin did in 2003, calling the new approach cliodynamics (on behalf of the muse of history, Clio). Using this method, Turchin himself established "secular" demographic cycles.
Linguistics
Andrey Zaliznyak. Photo: Mitrius/wikimedia
Every year in Novgorod, as well as in some other ancient Russian cities, such as Moscow, Pskov, Ryazan and even Vologda, more and more new birch bark letters are found, the age of which dates back to the 11th-15th centuries. In them you can find personal and official correspondence, children's exercises, drawings, jokes, and even love messages at all - "Attic" about the funniest ancient Russian inscriptions. The living language of letters helps researchers understand the Novgorod dialect, as well as the life of the common people and the history of Rus'. The most famous birch bark researcher is, of course, an academician of the Russian Academy of Sciences Andrey Zaliznyak : it is not for nothing that his annual lectures on newly found letters and deciphering the old ones are filled with a full hall of people.
Climatology
Vasily Titov. Photo from noaa.gov
On the morning of December 26, 2004, on the day of the tragic tsunami in Indonesia, which, according to various estimates, claimed the lives of 200-300 thousand people, an NSU graduate working at the Tsunami Research Center at the National Oceanic and Atmospheric Administration in Seattle (USA) Vasily Titov woke up famous. And this is not just a figure of speech: having learned about the strongest earthquake that occurred in the Indian Ocean, the scientist, before going to bed, decided to run a tsunami wave forecasting program on the computer and posted its results on the network. His prediction turned out to be very accurate, but, unfortunately, it was made too late and therefore could not prevent human casualties. Now the MOST tsunami forecasting program developed by Titov is used in many countries of the world.
Astronomy
Konstantin Batygin. Photo from caltech.edu
In January 2016, another news shocked the world: in our native solar system. One of the authors of the discovery was born in Russia Konstantin Batygin from the University of California. Having studied the movement of six cosmic bodies located beyond the orbit of Neptune - the last of those recognized on this moment planets, scientists using calculations showed that at a distance seven times greater than the distance from Neptune to the Sun, there must be another planet orbiting the Sun. Its size, according to scientists, is 10 times the diameter of the Earth. However, in order to finally be convinced of the existence of a distant giant, it is still necessary to see it with a telescope.
Mikhail Lukin's team created one of the most powerful quantum computers in 2017. With the help of a scientist, RBC understands what are the criteria for success in the quantum race and when to expect quantum superiority
Twenty years ago, quantum computers were considered science fiction, and soon they will surprise us no more than a regular PC. “I think that in five to ten years already in many areas human activity It will be impossible to do without quantum technologies,” says Harvard professor Mikhail Lukin, whose team created one of the most powerful quantum computers in 2017.
Mikhail Lukin left for America about a quarter of a century ago. In 1993, Marlan Scully, a world-renowned researcher in the field of quantum optics. In Texas in 1998, Lukin defended his thesis on the use of lasers to control the environment. But Mikhail Lukin made his main scientific experiments in the next decade at Harvard University. Here he became a professor of physics, then co-director of the Harvard Center for Quantum Physics and the Center for Ultracold Atoms.
“I was very lucky: at Harvard I was on special terms. Ordinary postdoc (a scientist who recently received a PhD, which roughly corresponds to a Russian Ph.D. — RBC) should work in one scientific group and be engaged in some specific highly specialized project. I had complete freedom, ”Lukin told RBC magazine.
Lukin says that he and his colleagues have been invited many times to work for corporations that have joined the race to create a quantum computer, but he invariably refuses: “I would say that so far the most creative activity in this area still takes place in universities.”
In an atmosphere of "work permissiveness" over the past 16 years, a scientist and his group have conducted experiments that have amazed the scientific world: like stopping light or creating photonic molecules - matter similar to Star Wars lightsabers - and time crystals, structures, before that existed only in theory. During these years, he also hatched the idea of the quantum computing experiment, which in the summer of 2017 made Lukin and his laboratory famous all over the world.
quantum informatics
Back in the early 1990s, the idea of creating quantum computers, even in the scientific community, was not taken seriously by anyone, says Lukin: “But then there were two, so to speak, revolutions at once.”
In 1994, the American Peter Shor developed the quantum factorization algorithm, which was later named after him. "multiply two prime numbers, even very large ones, is easy, but finding which prime factors dividing a large number is a very difficult task for a computer. Factorization is at the heart of all modern cryptography,” explains Lukin.
Photo: Photo: Sasha Maslov for RBC
Ordinary computers are capable of breaking modern cryptographic systems, but they take so many resources and time to do so that the result is useless. A quantum computer, on the other hand, will be able to solve such problems almost instantly, and Shor's algorithm became the first proof of the practical meaning of creating such devices. “Secondly, at the same time there were great advances in experimental physics: scientists learned how to cool atoms well, isolate individual particles,” continues Lukin.
In the same turning point for quantum computers in 1994, Research Article two European physicists, Peter Zoller and Juan Ignacio Cirac, in which they described a quantum computer using an ion trap. “Quantum informatics was just in its infancy, other researchers had only abstract ideas of quantum computers, no one seriously even thought about whether it could be done or not. The publication of Zoller and Sirak changed everything: it became clear that it was possible to build a quantum computer, and even a specific proposal appeared, ”recalls Lukin.
Mikhail met the authors of the article in the early 2000s: “They were already famous people, and I am a young novice scientist. But it turned out that our ideas are very similar. We joined forces and wrote a series of articles in which we theoretically described the ideas that formed the basis of our practical work today.”
In the 2000s, many scientific groups began to conduct experiments on superconductors - materials that completely lose their strength at low temperatures. electrical resistance. Lukin's group, in turn, decided to try to focus on "cold atoms" - particles cooled to almost absolute zero and placed in optical traps created by lasers. If the necessary conditions are met, they can be used as sufficiently stable quantum bits (qubits).
In the mid-2000s, Lukin did not dare to make a real quantum computer: the project seemed too risky, there was not enough technological base. For years, his group at Harvard has been exploring other ways to make qubits for a quantum computer, such as using impurities in diamond. Other practical projects emerged from such studies: for example, former students professors figured out how to make quantum sensors for medicine out of diamonds.
In the 2010s, quantum computing was no longer discussed exclusively in the laboratories of scientific centers - large IT companies were seriously interested in them.
Real quantum
A few years ago, the intention to build working prototypes of quantum computers was announced not only by IBM, which had been studying this area for a long time, but also by Google, Intel and Microsoft, which had not previously been seen in it.
At the same time, the Canadian company D-Wave has been producing and selling "real quantum computers" since 2011 - first with a capacity of 16, then 28, and a couple of years later - 512 qubits. Today the company already offers 2000-qubit computers. D-Wave has a serious pool of buyers: Google, NASA, Lockheed Martin, Volkswagen Group. To an uninitiated person, it may seem that the quantum future has already arrived - and yes, and no.
D-Wave produces so-called adiabatic computers - to understand their differences from full-fledged quantum computers, you will have to read at least short course quantum physics. In an applied sense, the difference lies in the fact that D-Wave computers are capable of solving only a very narrow range of optimization problems. Google, for example, picked up one problem for the D-Wave computer, which an adiabatic computer solved millions of times faster than a classical one. But it was impossible to extract real benefit from this, and the machine was not intended for solving other problems.
Successes in the field of creating "real" quantum computers are more modest: until recently, their power did not exceed 17-20 qubits, and Lukin says that a couple of years ago he did not believe in the possibility of creating a device with greater power. But in the summer of 2017, Lukin's group announced the creation of a working prototype of a 51-qubit quantum simulator, and just a month later, the group of Professor Christopher Monroe from the University of Maryland announced the creation of a 53-qubit simulator. The devices and the results of the first experiments carried out on them are described in an article published in the journal Nature at the end of November.
Atoms in optical traps and superconductors are today two technologies that are ahead of all other technologies for creating quantum computers, Professor Christopher Monroe told RBC magazine. “Both approaches are now at a stage where we already have a clear idea of how to build fairly large devices, and have ideas how to scale them,” he said. “Superconductors so far show lower performance, but since the qubits are printed on a chip here, they are easier to scale. Atoms are easier to work with because each atomic qubit is identical by definition. There are other, similar technologies that are catching up with us, including neutral atomic qubits, which are being made by Mikhail Lukin’s group.”
Race for qubits
The number of qubits seems to be a simple and straightforward criterion for success, but nothing in quantum physics is simple and straightforward. The number of qubits is just one of three "axes" on which a quantum computer is built, Professor Lukin explains. The second is coherence, the ability of qubits to be in a state of superposition (remember Schrödinger's cat), to be both zero and one at the same time - the whole theory of quantum computing is based on this phenomenon of quantum mechanics.
This ability determines the time during which the machine can work: the longer the coherence time, the more calculations the computer is able to perform. “If you have a million qubits, but you can’t do enough operations on them, then you won’t succeed in a quantum computer. For example, in D-Wave computers, each of the original qubits has such low coherence that it is not clear whether there are quantum properties at all or not,” Lukin says.
Finally, the third "axis" is the degree of programmability, it describes how many tasks different type with the help of a quantum computer it is possible to solve, continues Lukin. “Our simulator has fairly good coherence and quite big amount qubits, but other systems have all this. What is important is that we managed to make a system with a high degree of programmability,” he says.
The difference between a quantum simulator and a general-purpose quantum computer is that the former can only be programmed to perform certain kinds of tasks, Professor Monroe explains: “But the beauty is that the simulator can be turned into a general-purpose computer in the future.” True, it is not always possible to draw a clear line between them, Lukin adds.
“The quantum simulator, which can be programmed in any way, becomes universal. It turns out that the line between a computer and a simulator is very blurred, and now it is not clear whether it can be defined at all. But this is normal, we are now literally at the forefront of science, and this happens with all new phenomena, ”explains the scientist.
Optimism without evidence
Even scientists do not yet undertake to outline the entire range of tasks in which a quantum computer will surpass a conventional one. “Shor's algorithm is unique in a sense, because it is one of the few problems that we know for sure that a quantum computer will do it better than a conventional one, this has been proven. There are many other very promising algorithms, including those for the same combinatorial optimization, for which there is no evidence so far,” Lukin throws up his hands.
Photo: Photo: Sasha Maslov for RBC
On the one hand, it was the Shor algorithm and the inevitability of quantum hacking of cryptographic information protection systems that attracted a lot of public money to this area. Leading in this sense is China, which recently promised to invest $11.5 billion in the construction of a new quantum center. On the other hand, deciphering codes will become an important, but small part of what quantum computers can do, Lukin hopes. “What I don't like about Shor's algorithm is that it carries mostly destructive power. However, I am sure that even before it is implemented, the quantum computer will have time to bring many benefits to humanity,” he says.
In a late November paper in the journal Nature, scientists said they had seen the formation of quantum crystals, a material that could be used to create quantum memory in quantum computers. “What we have done cannot be directly simulated on classical computers; from this point of view, we can say that quantum superiority has already been demonstrated,” says Lukin. “This is important for science: we have already entered the limit when quantum computers begin to be useful.”
It is believed that quantum supremacy will be achieved when quantum computers perform practical tasks better than classical supercomputers. The power of classical computers is constantly growing, but there is a class of tasks that they still do not have enough resources to cope with, and this cannot be fixed by simply increasing computing capabilities, explains Lukin. Among them, for example, are combinatorial optimization problems that exist in any field.
“A classic example is the traveling salesman problem. Let's imagine that Aeroflot wants to optimize flight routes in such a way as to use less fuel and at the same time cover a large area and make flights convenient for passengers. A classical computer does not cope well with this type of tasks, they are too complex for it, there are too many answers. All he can do is take turns sorting out different variants, it takes a huge amount of time and requires a lot of power,” explains Lukin.
A quantum computer is able to sort through these options not sequentially, but in parallel, which fantastically speeds up the calculation process - literally minutes instead of years. Effectively solving such problems is extremely important for modern areas of computer science, such as artificial intelligence or machine learning, adds Lukin.
Among other possible applications of a quantum computer, physicists name the modeling of new materials with desired properties and various chemical processes. “Even simple chemical reactions are very difficult to model on classical computers, because there are so many options for their course,” explains Lukin. “Quantum computers are likely to be able to do this. Any efficiency gain chemical reaction literally a couple of percent capable of creating a new industry.” Monroe agrees with him: he sees the main prospects for quantum computing in logistics, the creation of new materials and drugs in pharmaceuticals, as well as in the most diverse optimization.
quantum internet
One of the main problems that physicists and engineers have to solve is the scaling of quantum computers. “Today, we don't know exactly how to scale these systems beyond about 1,000 qubits. There are different ideas, the most promising of them, in my opinion, is the idea of modular architecture, says Lukin. “Instead of adding more and more qubits to one machine, we create a network of quantum computers. Each computer with a power of a couple of hundred qubits is connected into something like a “quantum Internet”. Several groups are currently working on similar concepts, including Lukin's group, but all are in relatively early stages.
About 30 people work in Mikhail’s Harvard group, but there are much more people working on the quantum simulator: it was created by the joint efforts of three scientific laboratories. In total, according to Lukin, there are about ten such centers in the world, where developments are taking place at the forefront of quantum technologies. Most of them are now moving away from pure physical experiments towards practical developments, and the role of corporations is growing more and more. “In addition to pure science, we now need to solve engineering problems that can be clearly set, and this is done much faster and more efficiently in companies, and not in universities,” says Lukin. “We already know how to build a sufficiently large quantum computer, now we need to make the system work not at the level of “only a graduate student will figure it out”, but at the level of “came, turned it on, works.” It is in this, and also in search practical applications private companies are very strong.”
In the next five years, many working quantum machines will be created, Monroe is sure. And in ten years there will be a full-fledged quantum computer, programmable by people who do not know and do not particularly care about how it works inside, he believes: “It is then that the search for its real practical applications will begin.” Now universal quantum computers with a few tens of qubits can only work with artificially created algorithms, Monroe continues: “And this is not so interesting, because such a small system can be easily simulated on a conventional computer.”
Quantum computers are at the same stage that the first classical computers were at one time, Lukin says: “Peter Shor himself often talks about this: then there were also some ideas about algorithms that might maybe not". When the first classical computers became real devices, scientists and engineers began to test these algorithms on them, and many of them turned out to be very effective, says Lukin: “I think the same thing will happen with quantum algorithms.”
Will the quantum computer become the same familiar device as the ordinary PC has become? As long as no one knows, everything will depend on concrete examples and applications that can become part of our lives, Mikhail Lukin answers. “Who would have thought even 20 years ago that this would be a real computer,” he concludes, pointing to a cell phone in front of him.
