R eykjavik University Ne w Technology Spring 2006

Transcription

1 R eykjavik University Ne w Technology Spring 2006 Students March 19th 2006 Guðmundur Már Einarsson Hlynur Tryggvason

2 Table of Contents Introduction... 3 Basics of quantum computing... 3 Origins of quantum computing... 5 Recent advancements in quantum computing... 5 Current problems in quantum computing... 6 How does this technology relate to Moore s Law?... 7 Potential impact on software design and programming... 9 Potential impact on daily life... 9 Security issues...10 Searching...11 Business...11 Accessibility...11 Disruptive technology...12 Conclusion...12 References...13 Appendicies...15 Appendix A: to/from Charles Ross - former Secretary of the Quantum Computers in Europe Pathfinder Project Appendix B: to/from George I. Bourianoff senior program manager in the Strategic Research group at Intel

3 Introduction Moore s Law states that the power of microprocessors will double every 18 months. This has been valid for at least last 40 years and if it continues to hold, then today s chip manufacturing techniques will exhaust their capabilities by the year 2020, when a transistor would become no larger than the size of an atom. So the need for a new technology in building computers is clear if we are going to keep up with Moore s Law after 10 to 15 years. Enter quantum computing, potentially the next step of computer evolution. Functional quantum computer is a realistic option that could be available after 10 years or so. Quantum computers have the potential to become so powerful that problems which take today s computers years to solve would take minutes for a quantum computer. In this paper we look at the origins of quantum computing, see how they differ from todays computers and look at current problems in the field. Then we look at how quantum computers could extend Moore s Law and finally at the huge impact quantum computers could have if they would exist. For example, if one quantum computer would be available today, no information on the internet would be safe. Basics of quantum computing Almost every computer today is based on the Turing machine, developed by Alan Turing in the 1930s. The Turing machine consists of a tape of unlimited length that is divided into little squares where each square can hold one bit (0 or 1) or be left blank. A readwrite device reads these symbols and blanks which gives the machine its instructions. In a quantum turing machine the difference is that the tape and the read-write head exist in a quantum state, which means that each square can now hold one qubit which is either 0 or 1 or a superposition of 0 and 1 (being in a superposition basically means that the qubit can hold multiple values at the same time). Figure 1: Classical and Quantum Registers: (a) A comparison of a classical bit and a quantum bit. (b) Superposition states allow quantum registers to store all possible values simultaneously. [12] 3

4 Roughly speaking, a computer with N qubits has the processing power equivalent to a classical computer with 2 N classic bits. The table on the right might give some sense of the computing power a quantum computer might provide. Just to put things in perspective, if we would have a quantum computer with 300 qubits, then we would have states, approx. the same number of atoms in the known universe. [12] Qubits Equivalent Classic bits (2 Qubits ) = 8 KB = 512 MB Since each qubit can hold multiple values, it follows that a quantum computer can work on multiple computations at the same time, which gives us native parallelism. But now you must be thinking: I can listen to music, download movie trailers and work on my thesis at the same time on my computer, is this not parallelism?. It is a form of parallelism, but it is not native. Classic computers have gotten very powerful and are able to effectively simulate parallelism. But the fact remains that each processor (or each processor core if the processor has multiple cores) can only work on one computation at the same time. With quantum computers, it would essentially be possible to create a new processor for each application, process or thread that would require it. Although quantum computers have the potential of becoming a lot faster than Turingbased computers, they can be simulated using a Turing machine (given an unpractical amount of time and memory). This means that quantum computers cannot solve any problem that a Turing machine can t, such as the infamous halting problem [2]. Figure 2: Hypothetical high-level view of a quantum processor. [16] 4

5 Origins of quantum computing We don t have to go far back to find the origins of quantum computing. While computers have been around for the majority of the 20th century, quantum computing was first theorized just 20 years ago, by a physicist at the Argonne National Laboratory. [1] The idea of quantum computing came to be when scientist predicted the future of classical computation. If it would follow Moore s Law, then silicon chips would eventually be no larger than a few atoms. But that introduces a problem, because the classic laws of physics (those that silicon chips are based on) do not apply on an atomic scale. Fortunately, quantum mechanics apply on an atomic scale and because of that, scientist began to speculate on a new breed of computers based on quantum physics. [3] The first quantum algorithm was devised by Peter Shor, a research and computer scientist at AT&T s Bell Laboratories in New Jersey. The algorithm solves an important number theory problem, factorization, that many encription methods (such as RSA) are based on. In fact, if a working quantum computer would be devised that could run this algorithm, no information anywhere in the world would be safe! Fortunately, methods do exist that use quantum properties to encrypt data as well. [3] Recent advancements in quantum computing The most advanced quantum computers today have 7 qubits [1], meaning that they are still at the state. Government organisations such as USA s DARPA, the UK s Defence Evaluation and Research Agency, the Deutsche Forschungsgemeinschaft, and The European Union are spending a lot of money in research as well as the leading players in the information technology and networking industries in order to get closer to a real machine. [10] Physicists in academic labs and at firms such as IBM, HP and NEC have tried a variety of quantum computing approaches but none seems likely to deliver a working machine in less than 10 years. IBM currently owns the most advanced quantum computer, which can manipulate 7 qubits, meaning that they are still at the state [1]. Despite the difficulties that are currently associated with quantum computing, a company called D- Wave Systems plans to have a working quantum computer in three years [15]. The computer will not be fully functional quantum compuer but will be able to solve problems like the traveling-salesman problem in reasonable time. D-Wave Systems have already applied for some patents [14] in the field. 5

6 By the end of 2005, researchers at the University of Michigan pushed quantum computing closer to the real world with the fabrication of a key component, an ion trap. This ion trap is important because it can host a quantum bit (qubit), the fundamental element in quantum computing. This could be one way to mass-produce hardware for quantum computers. [4] So, every day we are getting closer and closer, although it is a fact that we are still many years off from functional quantum computer. Current problems in quantum computing Although a lot of progress have been made over the past few years, quantum computers are still in their infancy. For them to be practical in solving real-world problems, they would need have several dozens of qubits. [1] We contacted (by ) one of Intel s quantum researchers, George I. Bourianoff1 1, titled as senior program manager in the Strategic Research Group at Intel Corporation. One of the questions we asked him was Is quantum computing the future? His answer was: Quantum computing requires ultra low temperatures and is out of equilibrium with the room temperature background and can therefore be very low power. However, I personally feel that it is too difficult to maintain quantum state and quantum computing is many years off if ever. As seen by his answer, quantum computing can become very efficient in terms of power consumption and cooling, allowing for a lot higher clock speed in quantum processors than in current processors. Despite this fact, we are still facing a very difficult problem, error correction. Quantum computers have the tendancy to enter an inconsistent state just by being exposed to the environment. This is unavoidable since just by reading the state of a qubit will force it to decend from the superposition to become either 0 or 1, effectively destroying the data held in the superposition. In 1998, researches at Los Alamos National Laboratory and MIT managed to read the state of a single qubit without actually looking at it. [3] This is a significant milestone in quantum error correction and has given a lot of hope to researchers in the field. 1 George Bourianoff Bio: 6

7 Quantum hardware is also just in its infancy but is becoming more important to test the theories that have been introduced. Seth Lloyd, Professor of Mechanical Engineering at MIT is currently a prominent researcher in quantum hardware. [3] We sent him a query about his work by but unfortunately did not receive a response in time. How does this technology relate to Moore s Law? In 1965, Gordon Moore, co-founder of Intel, wrote an article on the future development of semiconductor industry for the 35th anniversary issue of Electronics magazine. In the article, Moore noted that the complexity of minimum cost semiconductor components had doubled per year since the first prototype microship was produced in This exponential increase in the number of components on a chip became later known as Moore s Law. [7] In 1980, Moore s Law started to be described as the doubling of number of transistors on a chip every 18 months. At the beginning of the 1990s, Moore s Law became commonly interpreted as the doubling of microprocessor power every 18 months.[8] And today, Moore s Law is so general that it basically says that the rate of technological development will double every 18 months. The demise of Moore s Law has been predicted repeatedly over the last few decades and now more and more papers and articles are written about the end of Moore s Law. Although Moore s Law has been valid for all this time, like everything else it must come to an end. If we assume that Moore s Law will continue to hold in the next few years, today's chip manufacturing techniques will exhaust their capabilities by the year 2020, when a transistor would become no larger than the size of an atom. [11] In 2003, four members of the Institute of Electrical and Electronics Engineers, Zhirnov, Cavin, Hutchby, and Bourianoff submitted a paper that proposed that we may be about to hit a wall when it comes to scaling electronics. Their paper, Limits to Binary Logic Switch Scaling - A Gedanken Model [9] describes that eventually the tunnelling of electrons and holes will become too great for the transistor to perform reliable operations so the two state of the switch would become indistinguishable. This cannot be allowed in a binary system, but it would happen if its size gets as small as 4 nm. Indeed, this would be the size of a transistor produced in 13 years, keeping strict adherence to Moore's Law. 7

8 As mentioned before we contacted George I. Bourianoff, which is one of the writers of this paper, now working as senior program manager in the Strategic Research Group at Intel Corporation and has special research interest in quantum computing. One of the questions we asked him was how Intel is going to respond to these facts he concludes in his paper. His answer was: Intel can project scaling along more or less conventional lines (some variant of the field effect transistor) for the next 15 years or so. Beyond that, we are looking for alternative technologies that can be integrated on to CMOS to extend Moore's Law which we are confident we will be able to do. This might answer why Intel and others have not been pushing so much on this new technology. The need is maybe not as urgent as some might think, they have all those years to go. This does not only apply to Intel, other chip manufacturers are confident that they will be able keep up with Moore s Law for at least the next ten years with current technology. In the paper mentioned above they add that the heat from these transistors will be very difficult to moderate, because to do so would require somehow diverting the heat produced by this device away from the processor. The entire processor could also be cooled but that would produce more heat than it takes away. The heat problem has not even been solved by other technologies. In the we got from Bouriannoff he adds: The exact nature of those technologies is not clear. However, we believe that we must look to alternative technologies which are out of equilibrium with the room temperature thermal environment. In the case of the binary switch, maintaining state against room temperature fluctuations requires an energy barrier of ~.02 ev and is responsible for the energy dissipation in switching. On the web we found frequent quotes from scientists saying that Quantum computing begins when Moore s Law ends and others saying quantum computing will extend Moore s Law. It doesn t matter how they formulate it, we can be pretty sure that Moore s Law will be valid for the next 10 years at least, but if we think any further than years it is 8

9 almost impossible to predict about the state of processing power. It s an obvious fact that we must find some new technology if we are going to keep up with Moore s Law after 15 years or so but if quantum computers become real we might see growth in processing power that goes way beyond Moore s Law. Potential impact on software design and programming With the increase of multi core processors, software designers and programmers are increasingly feeling the pressure of using design patterns that enforce consistency, especially when the software is doing a lot of things at the same time. The parallel nature of quantum computing also requires new design patterns that enforce consistency, which could result in a major rethinking in software design. On a lighter note, a classic procedural style programming language for quantum computers has already been designed and implemented [6]. This is very important in making the transisiton from classic to quantum computers for programmers because it allows for the implementation and simulation of quantum algorithms. It also shows that classic methods of programming apply also to quantum computers. In general though, quantum software will not be extensively studied until quantum hardware becomes a reality and thus, at this point, we can only speculate how software design would change with quantum computing. Potential impact on daily life Everybody agrees that the impact quantum computer would have is huge. Many specialists even conclude that the impact on technology would likely be as large as the impact of the transistor. In our investigation of the potential impact quantum computers could have we found multiple speculations of the technological impact, some of them even far, far from reality (at least to us). But what we found interesting is that not much seems to be written about the financial/economical impact quantum computers could or would have. We found one very interesting article called "The Potential Impact of Quantum Computing" [10] originally published in the Croner Business Networks Briefing in What made this different from other articles about this topic is the education of the authors. Charles Ross 2, co-author of this article, studied accounting, law and economics 2 Quantum Information Partners LLP - Charles Ross - 9

10 but has spent his career since 1958 in computing. So we decided to contact Charles in case he might have spent more time than others in investigating the possible financial/economical impacts of quantum computers. Charles replied quickly, telling us that recently he had moved more into Quantum Cryptography. He is currently writing a paper about Quantum Computing and sent us the first thoughts for the paper. In his paper there is a chapter called Immediate Threat where he says CTOs, CIOs and CSOs need to review their current strategies as stored archives of today s transmissions will be susceptible to decryption in the future. He also told us that together with some colleagues he set up Quantum Information Partner LLP and they have done some work for the Department of Trade and Industry. Last May they set up a presentation at the Bank of England of all the Quantum Cryptography systems now available. So it is obvious that the threat is real and organizations that rely on cryptography are watching out. Security issues If quantum computers would become true we would face a lot of security issues, for example many security codes, like passwords can be broken just by guessing, check the answer and then guess again until you got the right code (today in most cases you won t actually get infinitely many guesses, but let s assume so). Let s say there are n possible answers to check, then it would take an average of (n+1)/2 guesses to find the answer using today's computers. The only reason why this is okay is that it would in most cases take years to do. But the time for quantum computer to solve this problem would probably be counted in minutes if not seconds. [2] Today's cryptography algorithms are based on mathematical problems that are hard to solve with the existing algorithm technologies and computing power. The problem of factoring a large number Figure 3: Potential quantum computing impact. [10] 10

11 that has been made from the multiplication of two large prime numbers is the most widely used of those mathematical problems. Quantum computer could easily factor large numbers, and would therefore be extremely useful for decoding and encoding secret information. Our current methods of encryption are simple compared to the complicated methods possible in quantum computers. [1] For example, one method of secure quantum communication is based on the measurement property of quantum state (recall that just by reading data in a quantum state forces it do decend from the superpostition). If A would send a secret quantum key to B, then B could easily detect that the key was intercepted, because if someone had intercepted it, read it, and forwarded it again, then it would no longer be in a quantum state. Similarly, if that same someone would not be capture the photon carrying the key, copy it, and send the original to B, since copying of quantum state is prohibited in quantum mechanics. [12] Searching Algorithms [13] have been written that would allow a quantum computer to almost instantaneously search massive databases and return very precise results. If this would come true, things like web search would take much less time and return more precise results. Business Like we said earlier, not much seems to be written about the financial impact quantum computers would have. That is not really surprising as the quantum technology is still just in its infancy and has a really long way to go until it will, if ever, come true. Specialist do although suggest to businessmen that have companies which rely on secure transmission or cryptography to watch out for quantum computing. Accessibility Quantum computing could become so powerful that speech recognition could become much more reliable than it is today and effectively eliminate keyboards. Furthermore if quantum teleportation becomes a reality then the need for classic wired or even wireless networks would be eliminated. 11

12 Disruptive technology People seem to be careful before speculating about the possibility of quantum computing being a disruptive technology, maybe because everybody is in its own corner trying to be the first instead of telling others about their plans. But the potential for disruptive technologies in the quantum field is huge and can be seen just be measuring the number of companies that are currently investing in all kinds of patents [14] in this field. Among those companies there are many small venture companies but also the big ones like HP, IBM, Microsoft and more. Conclusion Although the principles behind quantum computers have been established and small model systems constructed, we are still a long way from practical working computers. Our research shows that quantum computing has immense potential and that engineers are confident that the remaining hurdles will be surpassed. Optimists believe that quantum computers will eventually become mainstream and significantly change the information and computing industry in terms of speed, security and even accessibility. This new theory brings up a huge challenge for physicists in building working quantum computers and for computer scientists to develop new algorithms and methods to use such devices. There seem to be at least 10 years until we will see quantum computers that can be compared to today's computers, but if the quantum computing dream will become true it will probably have huge impact on our lives. If we live long enough, we just might get to experience it. 12

13 References [1] How Quantum Computers Will Work. Howstuffworks. Retrieved February 10 th 2006, from Howstuffworks. [2] Quantum computer. (March 2006). Wikipedia. Retrieved February 10 th 2006, from Wikipedia, the free encyclopaedia. [3] The Quantum Computer. (April, 2000). Jacob West. Retrieved February 10 th 2006, from Computer Science at Caltech. [4] Quantum Hardware. (December 2005). Kate Greene. Retrieved March 19 th 2006, from Technology Review. [5] Bibliography on Quantum Programming Languages. (June 2005). Simon Gay. Retrieved February 10 th 2006, from Simon Gay's Bibliography on Quantum Programming Languages. [6] QCL - A programming Language for Quantum Computers. (March 2004). Bernhard Oemer. Retrieved February 10 th 2006, from QCL - A Programming language for Quantum Computers. [7] The Lives and Death of Moore's Law. (October 2002). First Monday. Retrieved March 13 th 2006, from First Monday. [8] Moore's Law. (March 2006). Wikipedia. Retrieved March 13 th 2006, from Wikipedia, the free encyclopaedia. [9] Limits to Binary Logic Switch Scaling A Gedanken Model. (May 2003). Victor V. Zhirnov, Ralph K. Cavin, James A. Hutchby and George I. Bourianoff. Retrieved March 13 th 2006, from Intel Exploratory Research. 13

14 [10] Impact of Quantum Computing. (November 1998). Z/Yen Limited. Retrieved March 14 th 2006, from Zyen. [11] Life after Moore's Law: Quantum computing. (October 2000). InfoWorld Test Centre. Retrieved March 13 th 2006, from InfoWorld. [12] The Development of Quantum Hardware for Quantum Computing. (July 2005). A. J. Daley, J. I. Cirac and P. Zoller. Retrieved March 19 th 2006, from Center for Quantum Optics and Quantum Information. [13] Rapid sampling through quantum computing. (Feb 2000). Lov K. Grover. Retrieved March 13 th 2006, from lanl.arxiv.org e-print archive mirror. [14] Patents in Quantum Computing. Quantum Fog. Retrieved March 14 th 2006, from Quantum Fog. [15] Quantum Calculation. (July 2005). Erika Jonietz. Retrieved March 14 th 2006, from Technology Review. [16] Quantum Computing Architecture Overview. Tzvetan S. Metodi. Retrieved March 19 th 2006, from Tzvetan S. Metodi s website. 14

15 Appendicies Appendix A: to/from Charles Ross - former Secretary of the Quantum Computers in Europe Pathfinder Project. Thank you for your . The Oxford Business School recently circulated a report on the commercial prospects for QIP. You can find it at Recently I have been more involved with Quantum Cryptography Original Message From: "Guðmundur Már Einarsson" <gudmundurme03@ru.is> To: <charles.ross@qipartners.com> Sent: Tuesday, March 14, :06 PM Subject: Quantum computing, paper. Hello Mr. Charles, Together with some colleagues I set up Quantum Information Partners LLP and we have done some work for the Department of Trade and Industry. Last May we set up a presentation at the Bank of England of all the Quantum Cryptography systems now available. We have just signed a Letter of Understanding with Oxford University to set up a commercial test bed to enable various organisations to design and engineer commercial applications as part of a prototype ultra high volume, ultra high security comms backbone. Try We have not updated our site with the above news. We only signed the LOU yesterday! Also attached is the first thoughts for a paper I have to give in the Autumn about QC. There is a bit more about Quantum Computing generally. I hope this is a help. We are two students at our last year for BSc in computer science doing a research paper in a course called "New technology" at Reykjavik University, Iceland. The subject of our paper is "Quantum computing". We were reading an article about the impact of quantum computing where you seem to be the writer. It was published in 1998 so much can have changed since then but we decided to send you as we found out that you are also interested in economics and financials. What we are thinking is what financial or economic impact you think quantum computers would have if they would become real? It would be a huge honour if you could send us few lines. Best regards, Gudmundur Mar Einarsson Hlynur Tryggvason Good luck with your BSc's. Let me know how you get on. What are you plans when you graduate? Charles Ross 15

16 Appendix B: to/from George I. Bourianoff senior program manager in the Strategic Research group at Intel Dear Gudmundur, The questions you ask are good questions. Intel can project scaling along more or less conventional lines (some variant of the field effect transistor) for the next 15 years or so. Beyond that, we are looking for alternative technologies that can be integrated on to CMOS to extend Moore's aw which we are confident we will be able to do. The exact nature of those technologies is not clear. However, we believe that we must look to alternative technologies which are out of equilibrium with the room temperature thermal environment. In the case of the binary switch, maintaining state against room temperature fluctuations requires an energy barrier of ~.02 ev and is responsible for the energy dissipation in switching. Quantum computing requires ultra low temperatures and is out of equilibrium with the room temperature background and can therefore be very low power. However, I personally feel that is too difficult to maintain quantum state and quantum computing is many years off if ever. What I feel may be possible is to use spin based systems which are naturally isolated from the thermal background (e.g. nuclear spin systems) or else use magnetic cooling on more conventional spin devices. There are many problems but I think the answer lies in this direction. I hope this helps, George -----Original Message----- From: Guðmundur Már Einarsson [mailto:gudmundurme03@ru.is] Sent: Monday, March 13, :43 AM To: Bourianoff, George I Subject: Quantum computing, paper. Hello Mr. Bourianoff, We are two students at our last year for BSc in computer science doing research paper in a course called "New technology" at Reykjavik University, Iceland. The subject of our paper is "Quantum computing". We found very interesting paper called "Limits to Binary Logic Switch Scaling-A Gedanken Model" where you are one of the writers. We decided to write you as we saw that your current research interest is in quantum computing. We would be really honour if you could spend a little time answering this ) In the paper you find out that eventually the tunnelling of electrons and holes will become too great for the transistor to perform reliable operations so the two states of the switch would become indistinguishable. (plus the heat problems) If we expect that Moore's Law will hold this would probably happen in the next years if our calculations are right. So our questions are these: What do you think will happen then? Is this the end of Moore's Law? Is it something that Intel is worried about? Is quantum computing the future? Hope you have time to send us few lines, Best regards, Gudmundur Mar Einarsson Hlynur Tryggvason 16