Sorting ultracold atoms in a three-dimensional optical lattice in a realization of Maxwell's demon
Sorting ultracold atoms in a three-dimensional optical lattice in a realization of Maxwell's demon
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DOI：
10.1038/s41586-018-0458-7
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发表时间：
2018-09-06
期刊：
影响因子：
64.8
通讯作者：
Weiss, David S.
中科院分区：
文献类型：
--
作者：
Kumar, Aishwarya;Wu, Tsung-Yao;Weiss, David S.
1872年，麦克斯韦提出了他著名的“恶魔”思想实验(1)。通过辨别气体中哪些粒子是热的、哪些是冷的，然后执行一系列可逆的动作，麦克斯韦妖可以将粒子重新排列成明显较低熵的状态。这种明显违反热力学第二定律的现象被二十世纪的理论工作解决了(2)：宇宙的熵在收集信息时经常会增加(3)，并且与恶魔的记忆相关的不可避免的熵增加(4)。思想实验的吸引力导致许多真实的实验被框定为恶魔般的。然而，过去的实验没有中间信息存储（5），仅产生系统熵的微小变化（6,7）或涉及四个或更少粒子的系统（8-10）。在这里，我们提出一个实验，它抓住了麦克斯韦思想实验的全部本质。我们从一个包含约 60 个原子的随机半填充三维光学晶格开始。我们使原子的振动足够冷，以便初始无序是主要的熵。在确定原子的位置后，我们执行一系列可逆操作来创建一个完全填充的子晶格，这显然是一个低熵状态。我们的排序过程将系统的总熵降低了 2.44 倍。这种高度填充的超冷阵列可以用作中性原子量子计算机的起点。
In 1872, Maxwell proposed his famous 'demon' thought experiment(1). By discerning which particles in a gas are hot and which are cold, and then performing a series of reversible actions, Maxwell's demon could rearrange the particles into a manifestly lower-entropy state. This apparent violation of the second law of thermodynamics was resolved by twentieth-century theoretical work(2): the entropy of the Universe is often increased while gathering information(3), and there is an unavoidable entropy increase associated with the demon's memory(4). The appeal of the thought experiment has led many real experiments to be framed as demon-like. However, past experiments had no intermediate information storage(5), yielded only a small change in the system entropy(6,7) or involved systems of four or fewer particles(8-10). Here we present an experiment that captures the full essence of Maxwell's thought experiment. We start with a randomly half-filled three-dimensional optical lattice with about 60 atoms. We make the atoms sufficiently vibrationally cold so that the initial disorder is the dominant entropy. After determining where the atoms are, we execute a series of reversible operations to create a fully filled sublattice, which is a manifestly low-entropy state. Our sorting process lowers the total entropy of the system by a factor of 2.44. This highly filled ultracold array could be used as the starting point for a neutral-atom quantum computer.