论文标题

使用融合测量值确定AKLT状态在量子处理器上的确定性恒定深度制备

Deterministic constant-depth preparation of the AKLT state on a quantum processor using fusion measurements

论文作者

Smith, Kevin C., Crane, Eleanor, Wiebe, Nathan, Girvin, S. M.

论文摘要

Spin-1 Affleck,Kennedy,Lieb和Tasaki(AKLT)模型的基态是矩阵乘积状态和受对称性拓扑阶段阶段的范式示例,并且还具有基于测量的量子计算的资源状态。 AKLT状态具有非零相关长度,不能由由本地门组成的恒定深入统一电路精确制备。在这项工作中,我们证明了可以通过通过融合测量来增强恒定深度电路来逃避这种无限限制,从而使总制备时间独立于系统大小和完全确定性。我们使用张量网络的语言阐明了我们的准备方案,此外表明,AKLT状态的$ \ Mathbb {Z} _2 \ Times \ Times \ Mathbb {Z} _2 $对称性直接为以前已知的准备方法提供了这种加速。为了证明在嘈杂的中间量子量子(NISQ)设备上测量辅助制备的实际优势,我们在IBM量子处理器上执行了协议。我们测量了准备好的AKLT链的弦顺序和纠缠频谱,并使用这些链作为指标,发现了比已知的(纯粹统一的)顺序制备方法的改进结果。我们以我们的测量辅助方案制备的AKLT状态进行了量子传送的证明。因此,这项工作提供了一种有效的策略,以AKLT状态的形式准备特定资源,并且更广泛地在实验上证明了通过基于测量的基于测量的电路深度降低NISQ时代设备可实现的状态准备的可能性。

The ground state of the spin-1 Affleck, Kennedy, Lieb and Tasaki (AKLT) model is a paradigmatic example of both a matrix product state and a symmetry-protected topological phase, and additionally holds promise as a resource state for measurement-based quantum computation. Having a nonzero correlation length, the AKLT state cannot be exactly prepared by a constant-depth unitary circuit composed of local gates. In this work, we demonstrate that this no-go limit can be evaded by augmenting a constant-depth circuit with fusion measurements, such that the total preparation time is independent of system size and entirely deterministic. We elucidate our preparation scheme using the language of tensor networks, and furthermore show that the $\mathbb{Z}_2\times\mathbb{Z}_2$ symmetry of the AKLT state directly affords this speed-up over previously known preparation methods. To demonstrate the practical advantage of measurement-assisted preparation on noisy intermediate-scale quantum (NISQ) devices, we carry out our protocol on an IBM Quantum processor. We measure both the string order and entanglement spectrum of prepared AKLT chains and, employing these as metrics, find improved results over the known (purely unitary) sequential preparation approach. We conclude with a demonstration of quantum teleportation using the AKLT state prepared by our measurement-assisted scheme. This work thus serves to provide an efficient strategy to prepare a specific resource in the form of the AKLT state and, more broadly, experimentally demonstrates the possibility for realizable improvement in state preparation afforded by measurement-based circuit depth reduction strategies on NISQ-era devices.

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