Computer Science 191 — Quantum Information Science and Technology (3 Units)

Course Overview


As an overview class, it provides a broad introduction to quantum computation theory, quantum algorithms, and physical implementations. As it is also cross-listed with Physics and Chemistry, the topics treated will not be extremely in-depth, since different sections of the class will appeal to different majors.


  • Math 54
  • Physics 7B
  • CS170

Although the prerequisites for the class don't seem to be much, it would be a lot more helpful coming in with some quantum physics background. Physics 7C is a good introduction, but it may not be enough. Much of the notation and concepts used in this class would actually be a lot easier to comprehend after taking Physics 137A first. Also, on the CS side, having taken CS170 provides some intuition in the algorithms section of the course, particularly with the Quantum Fourier Transform. However, even if you didn't have the above classes, the workload is light enough that you can play catch-up on your own time, if you are motivated enough to do so. It really doesn't matter when you take it, as long as you feel you have the necessary background for it.

Topics Covered

  • Basic axioms of quantum mechanics
  • Qubits and their properties; the Bloch sphere
  • Unitary transformations, tensor products, elementary gates
  • Entanglement, Bell states, quantum teleportation
  • Operators, observables
  • Pure states vs. mixed states, density matrices
  • Quantum cryptography
  • Quantum circuits & algorithms: Deutsch-Jozsa, Simon, Grover, QFT, Shor
  • Physical qubits: spin, resonance, precession
  • Modern physical implementations


Course Work

There is on average 1 short problem set a week consisting of about 4-5 problems. They are generally straightforward if you've been keeping up with lectures and the notes. Toward the end of the class, the problem sets will be replaced by an open-ended term project, which will involve doing some research into an area of quantum computation that you're interested in and coming up with a presentation and short report for that topic. In addition to the standard 3 hours of lecture and 1 hour of discussion a week, there are usually 1 to 2 midterms, but no final.

Time Commitment

The time commitment is rather light, and that is reflected by the fact that it is 3 units.

Choosing the Course

When to take

It is offered relatively sporadically. Take it if you have interest, though probably after sophomore year.

What's next?

None on the undergraduate side. Prof. Vazirani occasionally teaches the graduate version of this course as CS294 from time to time. That class is essentially a more sophisticated and in-depth version of what is covered here.

Usefulness for Research or Internships

Additional Comments/Tips

Don't fret if you don't completely understand something. Quantum mechanics is weird in itself, and it's hard enough that this class is cross-listed among three departments. You can always read up on the material by looking at the lecture notes or going to online sources--Quantiki is a good resource. Also, this is usually a small enough class so that questions are received well and office hours are easily accessible. In short, there's no need to worry about falling behind, since the pace is slow and everyone comes from a different background.

Last Updated: Summer 2020