Quantum Circuits for Dynamic Runtime Assertions in Quantum Computation

Abstract

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.

On Testing and Debugging Quantum Software

“…A compiler can automatically generate the code for the approximate copying (akin to compilers for CC that can instrument the code to add debugging information), translating higherlevel language into quantum assembly [91]. The same principle of multiple approximate copies (aggregated using statistics) can be used to generate runtime assertions [110,111,112,92].…”

A lightweight approach to detect malicious/unexpected changes in the error rates of NISQ computers

“…Statistical [12] and dynamic [15,30] assertions can be inserted by the quantum programmer primarily for debugging purposes. These assertions are based on inserting checkpoints into the circuits, which require measurements at different stages of the design.…”

“…Several approaches have been proposed to design quantum circuit assertions. In some approaches the measurement operations to test assertions impact the circuit output [12], while other assertions don't affect the circuit functionality but instead enhance the success probability of the output in the presence of errors [15,30].…”

“…Quantum circuit assertions include classical, superposition, and entanglement assertions [30]. Classical assertions check whether the qubits are in classical state (0 or 1).…”

Hybrid quantum-classical circuit simplification with the ZX-calculus

“…The description of quantum algorithms commonly involves quantum operations interacting with classical data in its inputs, outputs, or intermediary steps via measurements or state preparations. Some applications such as quantum error correction [9,2] and quantum assertions [18,25] explicitly introduce classical measurements and logic between quantum computations. In general, quantum programming languages usually allow for measurements and classically controlled quantum operators mixed-in with unitary gates [11,7,15,23].…”