Stabilizing Spin Coherence Through Environmental Entanglement in Strongly Dissipative Quantum Systems

TL;DR

This paper reveals how environmental entanglement in dissipative quantum systems can stabilize spin coherence, introducing a variational approach for the spin-boson model's ground state validated by numerical methods.

Contribution

It uncovers the role of environmental entanglement in stabilizing spin coherence and proposes a new variational method for analyzing the spin-boson model.

Findings

Environmental entanglement stabilizes spin coherence.

A fast-converging variational expansion is developed.

Numerical quantum tomography supports the approach.

Abstract

The key feature of a quantum spin coupled to a harmonic bath---a model dissipative quantum system---is competition between oscillator potential energy and spin tunneling rate. We show that these opposing tendencies cause environmental entanglement through superpositions of adiabatic and antiadiabatic oscillator states, which then stabilizes the spin coherence against strong dissipation. This insight motivates a fast-converging variational coherent-state expansion for the many-body ground state of the spin-boson model, which we substantiate via numerical quantum tomography.