Dynamics of a macroscopic spin qubit in spin-orbit coupled Bose-Einstein condensates

TL;DR

This paper investigates the spin dynamics of a macroscopic spin qubit in spin-orbit coupled Bose-Einstein condensates, revealing how interactions and spin-orbit coupling influence spin states and manipulation capabilities.

Contribution

It provides a detailed analysis of spin evolution in spin-orbit coupled BECs, highlighting the effects of interactions and initial phases on spin state space and control.

Findings

Spin Rabi frequency is unaffected by interactions at the Zeeman resonance.

Interactions and spin-orbit coupling create a three-dimensional spin state space.

Proper initial phases can modify spin dynamics and control.

Abstract

We consider a macroscopic spin qubit based on spin-orbit coupled Bose-Einstein condensates, where, in addition to the spin-orbit coupling, spin dynamics strongly depends on the interaction between particles. The evolution of the spin for freely expanding, trapped, and externally driven condensates is investigated. For condensates oscillating at the frequency corresponding to the Zeeman splitting in the synthetic magnetic field, the spin Rabi frequency does not depend on the interaction between the atoms since it produces only internal forces and does not change the total momentum. However, interactions and spin-orbit coupling bring the system into a mixed spin state, where the total spin is inside rather than on the Bloch sphere. This greatly extends the available spin space making it three-dimensional, but imposes limitations on the reliable spin manipulation of such a macroscopic qubit. The spin dynamics can be modified by introducing suitable spin-dependent initial phases, determined by the spin-orbit coupling, in the spinor wave function.