Ultrafast State Preparation via the Quantum Approximate Optimization Algorithm with Long Range Interactions
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Abstract
State preparation protocols ideally require as minimal a circuit depth as possible, in order to be implemented in near-term quantum devices. Motivated by long range interactions (LRI) intrinsic to many experimental platforms (trapped ions, Rydberg atom arrays, etc.), we investigate the performance of the quantum approximate optimization algorithm (QAOA) with LRIs for the preparation of non-trivial quantum states. We show that this approach leads to extremely efficient state preparation: for example, Greene-Horne-Zeilinger (GHZ) states can be prepared with O(1) circuit depth, and a quantum critical point of the long range transverse field Ising model (TFIM) can be prepared with > 99% fidelity on a 100 qubit system with only one iteration of QAOA. Furthermore, we show that QAOA with LRIs is a promising route for exploring generic points in the phase diagram of the long-range TFIM. Our approach thus provides concrete, ultrafast protocols for quantum simulators equipped with long range interactions.