Historical origins of quantum entanglement in particle physics

TL;DR

This paper systematically explores the historical development of quantum entanglement in particle physics, highlighting key experiments, theoretical insights, and the first demonstrations involving high-energy particles like kaons.

Contribution

It provides a comprehensive historical account of the origins and experimental realizations of quantum entanglement in particle physics, including the first entanglement of kaon pairs.

Findings

First controlled realization of spatially separated quantum entanglement in 1949 experiment

Introduction of entangled states of kaon pairs in 1958

Discussion of the implications of entanglement in high-energy particles

Abstract

In this paper, the historical origins of quantum entanglement in particle physics are systematically and thoroughly investigated. 1957, Bohm and Aharonov noted that the Einstein-Podolsky-Rosen correlation had been experimentally realised in the 1949 experiment of Chien-Shiung Wu and Shaknov. This was the first time in history that spatially separated quantum entanglement was explicitly realised in a controlled experiment. Wheeler first proposed such an experiment as a test of quantum electrodynamics, but his calculation was in error; the correct theoretical calculations came from Ward and Price, as well as from Snyder, Pasternack and Hornbostel, and the result was in accordance with Yang's 1949 selection rule. After the publication of Bell's inequality in 1964, it was considered whether it could be tested by using the Wu-Shaknov experiment. This gave an impetus to the field, and a new experiment was done by Wu's group, though it was not successful as a test of Bell inequality violation. In 1957, Tsung-Dao Lee, Reinhard Oehme and Chen Ning Yang established the quantum mechanical description of the kaons and found that the neutral kaon is a two-state system. In 1958, based on an approach similar to Yang's 1949 selection rule, Goldhaber, Lee and Yang were the first to write down the entangled states of kaon pairs, in which a single kaon can be charged or neutral. This gave, for the first time, quantum entanglement of internal degrees of freedom of high-energy particles other than photons. In 1960, as unpublished work, Lee and Yang discussed the consequences of quantum entanglement of neutral kaon pairs. We also describe several physicists in the past, especially Ward. A Chinese version of this paper was published in early 2023.