Exploring quantum coherence, spin squeezing and entanglement in an extended spin-1/2 XX chain

Abstract

In this study, we explore the ground state phase diagram of the spin-1/2 XX chain model, which features \(XZY-YZX\)-type three-spin interactions (TSIs). This model, while seemingly simple, reveals a rich tapestry of quantum behaviors. Our analysis relies on several key metrics. The ‘\(l_1\)-norm of coherence’ helps us identify coherent states within the phase diagram, which represent states capable of superposition and interference. We employ the ‘spin squeezing parameter’ to pinpoint unique coherent states characterized by isotropic noise in all directions, making them invaluable for quantum metrology. Additionally, we utilize the ‘entanglement entropy’ to determine which of these coherent states exhibit entanglement, indicating states that cannot be fully described by local variables. Our research unveils diverse regions within the phase diagram, each characterized by coherent, squeezed, or entangled states, offering insights into the quantum phenomena underling these systems. We also study the critical scaling versus the system size for the mentioned quantities.