This summer, Caltech's Thomas Vidick spent a month delivering a series of lectures about quantum cryptography… to an empty room. On October 9, students around the world will be able to enjoy them.

Vidick, assistant professor of computing and mathematical sciences in the Division of Engineering and Applied Science, is participating in a massive open online course (MOOC) that will be available, along with two other courses from Caltech, to thousands of students through the edX online education platform.

The class—CS/Ph 120, Quantum Cryptography—is cotaught by Vidick and his longtime colleague Stephanie Wehner from QuTech at the Delft University of Technology. Both Vidick and Wehner also will have classroom components to their courses, at their respective institutions.

Vidick says that he was inspired to teach the course through conversations with his PhD advisor at Berkeley, Umesh Vazirani, who taught a MOOC titled "Quantum Mechanics and Quantum Computation."

Vidick's course focuses on the ways in which quantum mechanics can be used to create secure lines of communication. Though the concept was first proposed in the 1970s, it has only recently gone mainstream, with the first quantum bank transaction taking place in 2004.

"It's a hot topic, but there are very few resources for people wanting to go beyond just the basics. Very few schools will even have a quantum cryptography course," Vidick says.

So far, CS/Ph 120 has 5,500 registered students—small, by the standards of MOOCs, which average 43,000 students, according to a 2014 study by a researcher at the Open University in the United Kingdom. Even so, Vidick expects that just about 200 will stick out the program to the end, given that the average completion rate for MOOCs sits around 6.5 percent.

For the dozen or so Caltech students and 40 Delft students who will attend in-person, the class will use the "flipped classroom" model, in which the lectures are done online, with time in the classroom spent cementing what the students have learned and diving deeper into the concepts.

While no prior knowledge of quantum mechanics is necessary, students will need to have a strong grasp of linear algebra, a branch of mathematics central to engineering, in order to follow along, Vidick says. "Making the course accessible does not mean dumbing it down, and the less mathematically inclined might find it challenging," he cautioned in a recent post to his personal blog, announcing the course.

The edX course launches on October 9, although in-class students already have begun meeting, to go over the basics of linear algebra, quantum information, computer science, and cryptography—concepts that will be used throughout.

Online, students will have access to video lectures, lecture notes, quizzes, and links to additional resources.

This will be Vidick's first MOOC and his first time teaching quantum cryptography—but he says he is looking forward to the challenge.

"Every time I finish teaching a class I want to teach it again right away, because it's like 'Now I know how to do it,'" Vidick says.

Students can enroll online at https://www.edx.org/course/quantum-cryptography-caltechx-delftx-qucryptox.