No, quantum field theory (QFT) is not a new and improved version of the aether idea. In fact, QFT and the aether concept are fundamentally different.
The concept of the aether was proposed in the 19th century as a hypothetical medium that was thought to permeate all of space. According to this idea, electromagnetic waves, such as light, were thought to propagate through the aether in a manner similar to how sound waves propagate through air. However, subsequent experiments, most notably the Michelson-Morley experiment, failed to detect any evidence of the aether, leading to its abandonment as a scientific concept.
On the other hand, quantum field theory is a theoretical framework in physics that combines quantum mechanics and special relativity to describe the behavior of fundamental particles and their interactions. In QFT, fields are the fundamental entities, and particles are considered as excitations or quanta of these fields. These fields exist in every point of spacetime and interact with each other through a set of mathematical rules.
Unlike the aether concept, QFT does not propose the existence of a physical medium that permeates space. Instead, it describes the behavior of particles and their interactions using mathematical formalism and the concept of quantum fields. QFT has been successful in providing a theoretical framework for understanding and making predictions about a wide range of phenomena, including particle physics, quantum electrodynamics, and the standard model of particle physics.
Therefore, while both the aether and quantum field theory have been concepts considered in the history of physics, they are distinct and represent different approaches to understanding the fundamental nature of the universe.