Coherent seeding of the dynamics of a spinor Bose-Einstein condensate: from quantum to classical behavior

Abstract

We present experiments revealing the competing effect of quantum fluctuations and of a coherent seed in the dynamics of a spin-1 Bose-Einstein condensate, and discuss the relevance of a mean-field description of our system. We first explore a near-equilibrium situation, where the mean-field equations can be linearized around a fixed point corresponding to all atoms in the same Zeeman state $m=0$. Preparing the system at this classical fixed point, we observe a reversible dynamics triggered by quantum fluctuations, which cannot be understood within a classical framework. We demonstrate that the classical description becomes accurate provided a coherent seed of a few atoms only is present in the other Zeeman states $m=\pm 1$. In a second regime characterized by a strong non-linearity of the mean-field equations, we observe a collapse dynamics driven by quantum fluctuations. This behavior cannot be accounted for by a classical description and persists for a large range of initial states. We show that all our experimental results can be explained with a semi-classical description (truncated Wigner approximation), using stochastic classical variables to model the quantum noise.

References in corpus (8)

• Twin matter waves for interferometry beyond the classical limit
• Detecting multiparticle entanglement of Dicke states
• Spinor Dynamics in an Antiferromagnetic Spin-1 Condensate
• Observation of Dynamical Quantum Phase Transition with Correspondence in Excited State Phase Diagram
• Magnetically tuned spin dynamics resonance
• Quantum Noise, Scaling and Domain Formation in a Spinor BEC
• Quantum-Fluctuation-Driven Coherent Spin Dynamics in Small Condensates
• Active SU(1,1) atom interferometry