  As the scale of quantum programs grows to match that of classical software,
the nascent field of quantum software engineering must mature and tools such as
debuggers will become increasingly important. However, developing a quantum
debugger is challenging due to the nature of a quantum computer; sneaking a
peek at the value of a quantum state will cause either partial or complete
collapse of the superposition and may destroy the necessary entanglement. As a
first step to developing a full quantum circuit debugger, we have designed and
implemented a quantum circuit debugging tool. The tool allows the user to
divide the circuit vertically or horizontally into smaller chunks known as
slices, and manage their simulation or execution for either interactive
debugging or automated testing. The tool also enables developers to track gates
within the overall circuit and each chunk to understand their behavior better.
Feedback on usefulness and usability from early users shows that using the tool
to slice and test their circuits has helped make the debugging process more
time-efficient for them.
