Quantum Computing is an enormous field and can be taught from many different perspectives. There are plenty of online quantum computing courses. These include the Introduction of Quantum Computing by St. Petersburg State University. Quantum Computing Courses, Quantum World by Harvard University.
The Building Blocks of Quantum Computer, by TV Delft. Quantum Computing Introduction, by TV Delft. QC101 Quantum Computing and Quantum Physics for Beginners. Quantum Computing: Theory of simulation and programming. The lessons in these programs help you to understand the mathematics model of quantum computers.
There are a number of quantum computing courses available online to allow one to get a certification on the subject. Some are free, and some are paid, but all have the end goal of providing the best information on the subject. One of the best is the Introduction to Quantum Computing by St Petersburg State University.
The course takes five weeks, with it being 2-4 hours a week. Another top course in quantum computing is QC101 Quantum Computing & Quantum Physics for Beginners. The course is 3.5 hours, and it can be enrolled in for a low rate through the platform Udemy.