Pancharatnam phase deficit can detect macroscopic entanglement

TL;DR

This paper introduces the Pancharatnam phase deficit as a novel tool for detecting macroscopic entanglement, including in superpositions of coherent states and distant spin singlets.

Contribution

It demonstrates that the Pancharatnam phase deficit can serve as an effective indicator of macroscopic entanglement, providing a new method for entanglement detection.

Findings

Pancharatnam phase deficit signals entanglement in macroscopic systems

It can detect superpositions of coherent states

It allows measurement of concurrence between distant spins

Abstract

The Pancharatnam phase deficit is defined as the difference between the Pancharat- nam phase acquired by the global system and the sum of the Pancharatnam phases acquired by subsystems during local unitary evolutions. We show that a non-zero value of the Pancharatnam phase deficit for a composite quantum system can be a signature of quantum entanglement. In the context of macroscopic quantum systems, we illustrate how the Pancharatnam phase deficit can be used to detect macroscopically entangled states. In particular, we use the Pancharatnam phase deficit to detect the entanglement for macroscopic superposition of coherent states. Furthermore, we show that by measuring the Pancharatnam phase deficit one can measure the concurrence of two spin singlets between distant boundaries.