Theoretical Physical Chemistry, University of Liège, 4000 Liège, Belgium.
The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
Proc Natl Acad Sci U S A. 2023 Mar 14;120(11):e2220069120. doi: 10.1073/pnas.2220069120. Epub 2023 Mar 10.
A quantum machine that accepts an input and processes it in parallel is described. The logic variables of the machine are not wavefunctions (qubits) but observables (i.e., operators) and its operation is described in the Heisenberg picture. The active core is a solid-state assembly of small nanosized colloidal quantum dots (QDs) or dimers of dots. The size dispersion of the QDs that causes fluctuations in their discrete electronic energies is a limiting factor. The input to the machine is provided by a train of very brief laser pulses, at least four in number. The coherent band width of each ultrashort pulse needs to span at least several and preferably all the single electron excited states of the dots. The spectrum of the QD assembly is measured as a function of the time delays between the input laser pulses. The dependence of the spectrum on the time delays can be Fourier transformed to a frequency spectrum. This spectrum of a finite range in time is made up of discrete pixels. These are the visible, raw, basic logic variables. The spectrum is analyzed to determine a possibly smaller number of principal components. A Lie-algebraic point of view is used to explore the use of the machine to emulate the dynamics of other quantum systems. An explicit example demonstrates the considerable quantum advantage of our scheme.
本文描述了一种接受输入并并行处理的量子机器。该机器的逻辑变量不是波函数（qubit），而是可观测量（即算子），其操作是在海森堡绘景中描述的。其核心是由纳米胶体量子点（QD）或点的二聚体组成的固态组件。导致其离散电子能量波动的 QD 尺寸分散是一个限制因素。机器的输入由一连串非常短的激光脉冲提供，至少有四个。每个超短脉冲的相干带宽需要跨越至少几个，最好是所有点的单个电子激发态。作为输入激光脉冲之间的时间延迟的函数，测量 QD 组件的光谱。光谱对时间延迟的依赖性可以通过傅里叶变换转换为频域。这个时间有限范围内的光谱由离散像素组成。这些是可见的、原始的、基本的逻辑变量。对光谱进行分析以确定可能更少的主要成分。使用李代数的观点来探索使用机器模拟其他量子系统的动力学。一个显式的例子展示了我们方案的相当大的量子优势。
