Spin squeezing of the non-Hermitian one-axis twisting model

TL;DR

This paper explores spin squeezing in a non-Hermitian one-axis twisting model, revealing conditions under which it surpasses Hermitian limits and discussing trade-offs like longer evolution times and success probabilities.

Contribution

It demonstrates that non-Hermitian OAT can achieve near-Hermitian TACT levels of spin squeezing, with dynamic regimes offering improved efficiency and success probabilities.

Findings

Achieves spin squeezing close to TACT limits in non-Hermitian OAT.

Dynamic regimes provide faster squeezing with higher success probability.

Steady state squeezing is limited to small systems due to decay probabilities.

Abstract

In the absence of decay, the conditional dynamics for an opensystem is often describable by a non-Hermitian Hamiltonian. This study investigates spin squeezing (SS) in non-Hermitian one-axis twisting (OAT) model. Somewhat surprisingly, SS close to the limit of Hermitian two-axis counter twisting (TACT) Hamiltonian is achievable for some parameters, which significantly improves upon the optimal value realizable by Hermitian OAT model. The drawback is like with all conditional schemes, it takes on average longer time to evolve into steady state, and the probability of no decay or success decreases as number of atoms (spins) increases. The result above for steady state SS in non-Hermitian OAT Hamiltonian is thus limited to small systems. For other parameter regimes, however, desirable SS arrives dynamically before steady state is achieved, with greatly shortened evolution time and enhanced probability of success, while still remain significantly improved over the limit of Hermitian OAT.