  In this paper, we propose quantum circuits for runtime assertions, which can
be used for both software debugging and error detection. Runtime assertion is
challenging in quantum computing for two key reasons. First, a quantum bit
(qubit) cannot be copied, which is known as the non-cloning theorem. Second,
when a qubit is measured, its superposition state collapses into a classical
state, losing the inherent parallel information. In this paper, we overcome
these challenges with runtime computation through ancilla qubits, which are
used to indirectly collect the information of the qubits of interest. We design
quantum circuits to assert classical states, entanglement, and superposition
states.
