Skip to 0 minutes and 4 secondsWelcome to "Understanding Quantum Computers." I'm Rodney D. Van Meter, of Keio University's Faculty of Environment and Information Studies. I'm Takahiko Satoh, of Keio University's Graduate School of Media and Governance. We are going to be your educators for this fascinating topic and we hope to get you through it using almost no math. By now, you have heard about quantum computers. Quantum computers have appeared quite a bit in recent science fiction. ‘Self-Reference Engine’, by Toh Enjoe, is one of my favorites, so is ‘Death's End’, by Liu Cixin. They have appeared in many others, including manga such as Eden. The representations aren't always accurate, but at least they heighten interest in the topic.

Skip to 0 minutes and 44 secondsOne of these may even be the reason that you are here. The story often goes something like this. Brilliant scientists in exotic labs are using the spookiest, most obscure effects of quantum mechanics to build science fiction computers, capable of practically anything. Quantum computers are going to break your encrypted internet connection. They are going to create an artificial intelligence that thinks at warp speed. Quantum networks are going to help us communicate faster than the speed of light and teleport objects, like, the transporter in ‘Star Trek’. Well, that's not quite true.

Skip to 1 minute and 17 secondsIn fact, faster-than-light communication is still impossible even using quantum mechanics and teleportation of objects looks to be impractical, though we do know how to teleport quantum information, still not faster than the speed of light, of course. Of all of these popular ideas, the only one that has some really solid basis is that quantum computers will impact the use of encryption. Quantum computing is going to change the world, and after three decades of research, practical systems may be just around the corner. We will discuss the motivation for building quantum computers, qualitatively cover the important principles in quantum computing and take a look at some of the most important quantum computing algorithms.

Skip to 1 minute and 54 secondsWe are going to learn how quantum computers can help chemists with their computations. Many companies need to optimize something. Their use of resources such as employee's time or material for manufacturing. Finding a route on a map is also an optimization problem. We will see where computers can and cannot help with problems like these. We will finish with a brief look at quantum computing hardware and the budding quantum computer information technology industry. This course is ideal for high school juniors and seniors and college freshmen and sophomores looking for a topic of study as well as practicing computer professionals interested in learning about one of technology's most exciting topics.

Skip to 2 minutes and 33 secondsLay people with an interest in popular science will have no problem keeping up. The expected time to complete the course is about 10 to 15 hours over 3 weeks, about the time it would take you to read a medium-length book on the topic. The field lies at the intersection of computer science, physics and mathematics. Being able to conduct research at the leading edge, as in any field, requires a lot of intense preparation but in this course, we will help you take the first steps in understanding the topic whether you hope to work in the area or are just curious.

Skip to 3 minutes and 7 secondsFortunately, we won't go into the mathematics, beyond what you have already learned in high school. If you know what a sine wave is, can multiply to get powers of two, can add two vectors, and know enough probability to talk about rolling dice, you know enough to get through this course. Imaginary numbers will make a cameo appearance, but you really don't need to know anything serious about them. On the computer science end, it is helpful if you know how to count in binary, but that's about it. No physics background is assumed beyond a rough idea of what photons, electrons and atoms are. So, let's get started!


After twenty years as a subject of quiet academic research, suddenly talk about quantum computers is everywhere. You can use a quantum computer via the web, and perhaps soon buy one. Would you like to learn how they work?

What’s a quantum computer?

Okay, maybe we should pause to tell you what a quantum computer is. Simply put, it’s a computer that uses quantum effects to calculate the results of some functions far faster than an ordinary (classical) computer can. That’s really not a lot of help, though.

You have probably heard that, in quantum mechanics, an electron or a photon sometimes behaves like a particle, and sometimes like a wave. Light makes beautiful patterns on a soap bubble thanks to waves, but we can also count photons one by one. Researchers all around the world are investigating a bunch of different ways to build quantum computers, but they all have this in common: a quantum computer takes advantage of both the wave nature and particle nature, using interference and quantum entanglement, to reduce the number of times we have to perform some calculation.

The excitement comes from their behavior as problems get harder: maybe increasing the size of a problem (for example, boosting the number of cities you are planning to visit on a trip by one) doubles the amount of time it would take a regular computer to find your best route, but only raises the time on a quantum computer by, say, twenty seconds. The actual size of the advantage a quantum computer has depends on a lot of factors, though, and you will learn about some of them in this course.

A three week journey

In this course, we will dive into quantum computing head first, but not without preparing. In Week 1, we will study the key concepts, beginning with how waves interfere with each other and leading toward quantum entanglement, which Einstein called “spooky action at a distance”. In Week 2, we will learn how quantum computers compute, by studying some of the important quantum algorithms. In Week 3, we will learn how quantum computers are becoming a reality. We will visit the labs of several professors who are developing several kinds of quantum technologies, learn how errors are handled, see where research is being done and find out which companies are trying to build computers.

Each week, you will watch videos and read articles, answer quizzes and discuss with your fellow learners. Some quizzes will use interactive applications to help you understand concepts and answer questions, and designs for several 3-D printable objects are provided both for fun and to help vision-impaired learners.

Join us on our three-week journey into one of the twenty-first century’s most exciting technologies!

Organizing team

This course will be led by Associate Professor Rodney Van Meter and Project Research Associate Takahiko Satoh from Keio University.

Educators and Organizers From the left: Rodney Van Meter and Takahiko Satoh.

Motoki Yasui from Keio University Press, Dr. Shota Nagayama, Takaaki Matsuo from Master student at Keio University, and Professor Keiko Okawa from the Graduate School of Media Design, will assist you during the course!

Follow the team to read their responses to learners throughout the course.

Important notes

  • You can find a PDF version of all the steps of the week in the “DOWNLOADS” section of the first step of the each week.
  • We have included a glossary for your reference. You can consult the glossary by downloading the PDF version which is available from the “DOWNLOADS” section below. If you come across other words that you would like us to add to the glossary, please tell us in the comments section.
  • When you complete each step, select the Mark as complete button before selecting the forwarded arrow to move on.
  • If you are new to FutureLearn, take a look at the Using Futurelearn section for information on how to get the best out of the course.

Complete the pre-course survey

To help us understand why you’re taking this course and make sure we meet your needs, please take a few minutes to complete FutureLearn’s pre-course survey if you have not done it yet.

Get extra benefits, upgrade your course

You can now get extra benefits by upgrading this course, including:

Unlimited access to the course: Go at your own pace with unlimited access to the course for as long as it exists on FutureLearn.

A Certificate of Achievement or Statement of Participation: To help you demonstrate your learning we’ll send you a Certificate of Achievement or Statement of Participation when you become eligible.

Find out more

Share this video:

This video is from the free online course:

Understanding Quantum Computers

Keio University