Nuclear spin squeezing via electric quadrupole interaction

TL;DR

This paper explores how electric quadrupole interaction (QI) can be used to control and optimize nuclear spin squeezing in solid-state systems, revealing new regimes and effects relevant for quantum information processing.

Contribution

It demonstrates that increasing EFG biaxiality enables continuous tuning of nuclear spin squeezing from one-axis to two-axis twisting, providing detailed analysis and potential applications.

Findings

EFG biaxiality allows tuning of spin squeezing regimes

Dephasing leads to anti-squeezed terminal states

Beat patterns in squeezing observed in 2D EFG with magnetic field

Abstract

Control over nuclear spin fluctuations is essential for processes that rely on preserving the quantum state of an embedded system. For this purpose, squeezing is a viable alternative, so far that has not been properly exploited for the nuclear spins. Of particular relevance in solids is the electric quadrupole interaction (QI), which operates on nuclei having spin higher than 1/2. In its general form, QI involves an electric field gradient (EFG) biaxiality term. Here, we show that as this EFG biaxiality increases, it enables continuous tuning of single-particle squeezing from the one-axis twisting to the two-axis countertwisting limits. A detailed analysis of QI squeezing is provided, exhibiting the intricate consequences of EFG biaxiality. The initial states over the Bloch sphere are mapped out to identify those favorable for fast initial squeezing, or for prolonged squeezings. Furthermore, the evolution of squeezing in the presence of a phase-damping channel and an external magnetic field are investigated. We observe that dephasing drives toward an anti-squeezed terminal state, the degree of which increases with the spin angular momentum. Finally, QI squeezing in the limiting case of a two-dimensional EFG with a perpendicular magnetic field is discussed, which is of importance for two-dimensional materials, and the associated beat patterns in squeezing are revealed.