The theory of quantum algorithms promises unprecedented benefits of harnessing the laws of quantum mechanics for solving certain computational problems. A persistent obstacle to using such algorithms for solving a wide range of real-world problems is the cost of loading classical data to a quantum state. Several quantum circuit-based methods have been proposed for encoding classical data as probability amplitudes of a quantum state. However, they require either quantum circuit depth or width to grow linearly with the data size, even though the other dimension of the quantum circuit grows logarithmically. In this paper, we present a configurable bidirectional procedure that addresses this problem by tailoring the resource trade-off between quantum circuit width and depth. In particular, we show a configuration that encodes an $N$-dimensional state by a quantum circuit with $O(\sqrt{N})$ width and depth and entangled information in ancillary qubits. We show a proof-of-principle on five quantum computers and compare the results.

中文翻译：

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用于量子态制备的可配置次线性电路

量子算法理论为利用量子力学定律解决某些计算问题带来了前所未有的好处。使用此类算法解决广泛的现实世界问题的一个持续障碍是将经典数据加载到量子状态的成本。已经提出了几种基于量子电路的方法来将经典数据编码为量子态的概率幅度。然而，它们需要量子电路深度或宽度随数据大小线性增长，即使量子电路的另一个维度以对数方式增长。在本文中，我们提出了一个可配置的双向过程，通过调整量子电路宽度和深度之间的资源权衡来解决这个问题。特别是，我们展示了一种配置，该配置通过具有 $O(\sqrt{N})$ 宽度和深度以及辅助量子位中的纠缠信息的量子电路对 $N$ 维状态进行编码。我们在五台量子计算机上展示了原理验证并比较了结果。