Quantum 2025 – scientific programme
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TUE: Tuesday Contributed Sessions
TUE 6: Quantum Computing and Communication: Contributed Session I (Algorithms & Theory)
TUE 6.3: Talk
Tuesday, September 9, 2025, 14:45–15:00, ZHG007
Quantum Approximate Optimization via Weak Measurements — •Tobias Stollenwerk1 and Stuart Hadfield2 — 1Forschungszentrum Jülich — 2NASA Quantum Artificial Intelligence Laboratory
Algorithms based on non-unitary evolution have attracted much interest for ground state preparation on quantum computers. One recently proposed method makes use of ancilla qubits and controlled unitary operators to implement weak measurements related to imaginary-time evolution. In this work we specialize and extend this approach to the setting of combinatorial optimization. We first generalize the algorithm from exact to approximate optimization. We then show how to modify the paradigm to the setting of constrained optimization for a number of important classes of hard problem constraints. For this we adapt the algorithm to penalty-based approaches and elucidate the resource overhead. As an alternative approach we show how one may design and employ operators that preserve the subspace of feasible problem solutions in order to to avoid the overhead of penalty terms. In particular, we show that mixing operators from the quantum alternating operator ansatz may be directly imported, both for the necessary eigenstate scrambling operator and for initial state preparation, and discuss quantum resource tradeoffs. Finally, we consider the effects of hardware noise and propose further algorithmic variants towards ameliorating its effects.
Keywords: Quantum Computing Algorithms; Quantum Optimiization; Quantum Simulation