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Embedding quantum optimization problems using AC driven quantum ferromagnets
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DOI：10.1088/1402-4896/ae5fec.png)
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Abstract
En 中文
Analog quantum optimization methods, such as quantum annealing, are promising and at least partially noise tolerant ways to solve hard optimization and sampling problems with quantum hardware. However, they have thus far failed to demonstrate broadly applicable quantum speedups, and an important contributing factor to this is slowdowns from embedding, the process of mapping logical variables to long chains of physical qubits, enabling arbitrary connectivity on the short-ranged 2d hardware grid. Beyond the spatial overhead in qubit count, embedding can lead to severe time overhead, arising from processes where individual chains ‘freeze’ into ferromagnetic states at different times during evolution, and once frozen the tunneling rate of this single logical variable decays exponentially in chain length. We show that this effect can be substantially mitigated by local AC variation of the qubit parameters as in the RFQA protocol (Kapit and Oganesyan, Quant. Sci. Tech. 6, 025013 (2021)), through a modified protocol we call Symphonic Tunneling. We provide general arguments and substantial numerical evidence to show that addition of AC terms in the Hamiltonian accelerates multi-qubit tunneling significantly. We explore schemes to synchronize the AC tones within chains to further improve performance. Implemented at scale, these methods could significantly improve the prospects for achieving quantum scaling advantages in near-term hardware.
Keywords:
quantum optimization
quantum annealing
embedding
AC-driven quantum ferromagnets
tunneling acceleration
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