Quantum computers could change civilization as we know it
Dr. Kaku Talks on Quantum Computers
By Mi Alun, for ChinaByte.Com
Q: is question by Mi Alun
A: is answer by Kaku.
Since last year, there have been more and more news reports on quantum computers, regarded as the top force to develop info-technology in the next 20 years. What is a quantum computer? Is it just a big upgrade from the conventional computers we are now using? How does it work? The development of quantum computer technology is called a “revolution” in most information industries. What is this revolution? To get answers, I recently interviewed Dr. Michio Kaku.
Dr. Kaku is familiar to the academic community and many science readers in China. He is the Henry Semat Professor of Theoretical Physics at the City College of New York. Dr. Kaku is a co-founder of string field theory that is one of the most advanced studies in today’s high-energy and theoretical physics. He is the author of the critically acclaimed and bestselling Hyperspace, as well as Visions -- How Science Will Revolutionize The 21st Century, also a best-seller in several countries. Both have been translated into Chinese. Dr. Kaku also hosts an hour-long weekly radio science program that is nationally syndicated in the United States. He lives in New York City with his wife and two children.
The following are scripts from my interview with Dr. Michio Kaku.
Q: Dr. Kaku, as a leading expert in high-energy physics, would you please explain what “quantum computer” is?
A: Moore’s Law (which states that computer power doubles every 18 months) has revolutionized every aspect of human society. It has held for the past 50 or so years. However, it will collapse around 2015 to 2020. This is because silicon components cannot function at the molecular level. (For example, wires that are less than 5 atoms across will leak electrons, making them useless.)
This, in turn, has created much anxiety among computer scientists, because Silicon Valley, the source of so much wealth, may become a Rust Belt after 2020. By then, new computer architectures will be competing to take the mantle away from silicon chips. Some proposals include: DNA computers, molecular computers, protein computers, optical computers, quantum dot computers, and quantum computers. But the strangest, and most powerful, of all these computers is the quantum computer.
Q: Based on conventional computer, built by 0 and 1, a binary system, we call our time “digital age”. As quantum computers become available, is our “digital age” going to become “quantum age”?
A: All previous computers were based on a binary system. Any system which can exist in two states (such as 0 and 1, or off and on, or up and down) can in principle be used to create a binary computer (sometimes called a Turing machine). These computers store information in the form of “bits”, representing 0 or 1. However, the only exception to this rule is the quantum computer.
Simply put, a quantum computer can be built by shining a laser light on a string of atoms placed in a magnetic field. By analyzing the reflected laser light, we see that it contains a tremendous amount of information concerning the orientation of the various atoms. Hence, it has performed a very complex calculation. By measuring how the laser light is reflected, one has performed a quantum calculation.
More precisely, these atoms can be spinning in the up or down direction, like a spinning top. As the laser light hits the atoms, it flips the spins of some of the atoms and is reflected. The reflected laser light contains the “information” of the scattering process (which flipped the direction of the spins).
But the key point is that the atoms do not really point either up or down. Since they obey the strange laws of quantum mechanics, they are actually a mixture of up and down states. We call them “qubits” because they are not really 0 or 1 (but represent something “in between”). Since they are based on atoms and qubits, they can in principle perform much more complicated calculations than standard Turing machines.
Hence, quantum computers are not digital computers at all. They represent a startling departure from the usual Turing machine.
Q: Conventional computers continue to grow their speed, memory and other powers. Why do we need quantum computers? And why don’t we have them now?
A: One simple application of the quantum computer would be to break complicated codes. Multinational banks, the police, and CIA, etc. are all interested in how codes can be broken and protected.
Many secret codes are based on factorizing long numbers. For example, if we are given a number with 100 digits, it will take a digital computer a long time to see if it is the product of two smaller integers. Hence, banks could send billions of dollars in transactions across “secure” cables, knowing that any criminal would have to factorize 100 digit numbers in order the crack the code.
In principle, however, it can be shown mathematically that a quantum computer can crack even these difficult problems effortlessly.
Unfortunately, for all the promise of quantum computers, they really don’t exist, at least in the form that we desire. There are many problems facing quantum computer scientists. First, there is the problem of obtaining pure states of atoms. Even the tiniest disturbance (e.g. a random cosmic ray) can ruin the coherence of the string of atoms being analyzed. Hence, quantum computers would have to be exceptionally shielded to protect them from the slightest atomic disturbance.
Second, there are the practical problems of manipulating strings of individual atoms. Only in the last decade have scientists been able to reliably manipulate individual atoms.
So far, scientists have been able to show that the fundamental principles of quantum computers are sound. Although some scientist were skeptical at first, simple prototypes have convinced the scientific community that a quantum computer is possible. However, this is a far cry from building one which can do practical applications!
Q: What can we expect regarding quantum computer development?
A: In the next decade, we expect to see this rapidly moving area scoring breakthroughs as primitive quantum computers are developed. However, realistically, it may take several more decades before we develop a quantum computer that can exceed the power of silicon chips.
But once genuine quantum computers are available, they show much promise. Not only can they be used by the governments of various nations to break or analyze codes, they might also be used to solve problems which are beyond the power of silicon, such as artificial intelligence. At present, digital computers have been totally unable to solve the “common sense” problem that lies at the heart of artificial intelligence. It would take a super digital computer armed with several hundred million lines of common sense to be able to duplicate the common sense of an 8 year old child. Perhaps the quantum computer can help in this area.
Q: Since quantum computing is so powerful, one can use it to quickly break any password or encryption codes made in current computer platforms. What’s the impact on security issues? Will we have any privacy in the future?
A: Some people worry that, with all this power, we will never have any privacy. Big Brother will be replaced by Little Brother, as every busy-body gains access to our files.
However, here quantum physics comes to the rescue. One can also use the principle of the quantum theory to create fiber optic cables which can detect the slightest amount of tampering. For example, if we send polarized laser light down a glass fiber, and someone tries to “listen in” to the message, the polarization of the laser light will be altered, and hence one can determine that someone is listening in. In fact, by the Heisenberg Uncertainty Principle, one can show, beyond a shadow of a doubt, that someone is trying to tap into your line.
This method, called quantum cryptography, has already been shown to work over many miles of fiber optic cable. Hence, in the future, banks and governments may send their secret messages on glass fibers and use quantum cryptography to make sure that no one is listening.
Other people have suggested that quantum computers can be used to decipher messages from aliens in outer space. Already, at Berkeley, scientists have signed up almost a million computer owners to be part of their set-at-home project. While their PC’s are idle, the computer program takes over the computer and uses it to decipher signals received by the Arecibo radio telescope in Puerto Rico. At present, this has become the largest running computer program in the history of computers. (Personally, I believe that even a quantum computer won’t help here. Any advanced civilization will take their messages and spread it across the entire spectrum.
In this way, local disturbances, like a supernova, may destroy one frequency, but not the whole message. Then, at the other end, the receiver will re-assemble the message. If we listen in on this conversation with a single frequency, we hear only gibberish. Hence, the galaxy could be teeming with messages, and we are too primitive to know this!)
Q: What about software?
A: Another challenge for quantum computers will be writing software for them. Usually, software was written to conform to a deterministic, digital computation based on bits. Since quantum computers use qubits, not bits, we have to devise a new way in which to program quantum computers.
Q: Conventional computer, which we are using now, can work no matter in summer or winter, no matter in an office or in a wild field, for the chips in the computer are superconductors. Atoms, according to quantum physics, can be easily lost in control. Practically, how can we use an atom-based quantum computer in a normal environment?
A: Complicated calculations with quantum computers require hundreds, perhaps thousands to millions of atoms acting coherently and in unison. That is the ultimate goal of quantum computers. Once this is achieved, then calculations that appear to be like “magic” today will become common place. Society itself may be changed beyond recognition when this is achieved.
But that is also the key problem. Once we have more than just a few interacting atoms, we find that the system interacts with the environment and is disturbed, thereby losing its coherence. This is the famous de-coherence problem. Isolating these delicate systems from interactions with the outside world is an exceedingly difficult problem.
In fact, at present, scientists can only perform calculations on just a few atoms at a time, before interference effects from the environment disrupt the system. This is a purely practical problem (not one of principle) but nonetheless it is the main obstacle facing quantum computers. In other words, we know that in principle everything works, just like the theory predicts. The problem is that our laboratories are not sophisticated enough to create pure collections of coherent atoms.
Q: According to news reports, actual quantum computers are projected for 5 years. Are we going to see it in the next 5 years?
A: Although there are many optimistic projections about the future of quantum computers, these projections refer to perhaps tens of atoms acting coherently together. We will see, therefore, remarkable breakthroughs being made in the next 5 to ten years, as scientists build quantum computers with tens of atoms acting coherently. New and increasingly difficult problems will be solved in this time frame.
But the ultimate dream of having hundreds, indeed, thousands and millions of atoms acting coherently is a tantalizing one, but still one that may take decades. This ultimate dream is keeping the field very much alive and active, with scores of scientists in the top laboratories around the world chasing after the Holy Grail of quantum computers: creating coherent systems with thousands to millions of interacting atoms. The goal is still a distant one, but when that happens, it could change civilization as we know it.
Q: Your book, “Visions”, has been well received in several countries, and also translated into Chinese. In that book, you discussed various types of computer revolutions in the 21st Century. Why do you call it a “revolution”?
A: I’ve interviewed 150 of the world’s top scientists for my book, Visions: How Science Will Revolutionize the 21st Century (available in Chinese). The book became a best-seller in several countries. These scientists, who are inventing the future in their laboratories, tell me that the future is limitless for those nations which see science and technology as their way out of poverty.
This is important, because more and more the nature of international finance and capitalism is changing. Under the old system of Adam Smith, wealth was based on labor and natural resources. However, commodity prices have been dropping for the past 70 years, and will continue to drop into the 21st Century. Gradually, the source of wealth is shifting away from commodity capital towards intellectual capital. This means, for example, that nations which are “rich” today with natural resources may find their economies turn to dust, if they neglect intellectual capital. Nations which are poor today may find themselves rich in the future if they invest in
a) the Internet and telecommunications
b) education for their people
c) funding for research in information technologies and DNA research.
This means that nations which were relatively poor in the past century can leapfrog over more advanced nations. For example, by using satellites, one can leap ahead of countries which painfully wired up their people, home-by-home. This means that developing nations should embrace these new technologies (even though it may disturb the more traditional sectors of their society).
Science and technology are some of the main sources of wealth in society. Any society which fearlessly encourages the development of science and technology will find themselves rich and prosperous in the 21st century.
Q: Since U.S.-China normalization 20 years ago, you have taught many Chinese students. What do you think about them?
A: In the past 20 years, I have taught Chinese students from China. I find them to be very studious, dedicated, and smart. They are comparable to the finest students found anywhere on earth. More important, they are open to new ideas, and rapidly catch up with students from more developed countries. Reading journal articles from major universities, one constantly hears the names of Chinese students who have successfully joined major research groups. (The End)
