Students watch as oscillating line graphs pop up on a computer screen, measuring the photons emitted by defects in a thin slice of diamond. They confer before tweaking the code that dictates the pulsing of a laser, manipulating the qubits stored in the defects.
This hands-on lesson in writing computer code to control scientific instruments is a key part of the course “Experimental Methods in Quantum Computing,” offered for the second time in fall 2022. Electrical and computer engineering professors Jeff Thompson and Nathalie de Leon developed the course to help undergraduates and first-year graduate students gain experimental skills as a foundation for future work in quantum science and engineering.
They intentionally designed open-ended lab exercises, said Thompson. “We gave them the parts that they would need to do an experiment, but then encouraged them to tinker and figure out how to do it.”
The course introduces students to three types of qubits: nuclear spin qubits, electron spin qubits based on defects in diamond, and superconducting qubits. Students experiment with the first two using scaled-down versions of research lab setups. And by writing code to remotely control an IBM machine, they send microwave pulses to control a superconducting qubit and measure its properties.
In her lab, de Leon’s team uses optical setups the size of a dining table, which offer flexibility for different experiments. For the course, she worked with graduate student Zhiyang Yuan to “strip down a lot of the components and try to make it really small and robust,” said de Leon.
After learning the basics of the different qubit platforms, the students work in small groups on projects of their choosing. In the inaugural spring 2022 course, one group explored a two-qubit system on an IBM machine — building on the experiments they had done with a single qubit and beginning to probe the types of circuits that can process quantum information.
Working through qubits’ fundamental properties “gives you really good intuition for everything else” in quantum research, de Leon said.