Chaos and Entanglement with Two Coupled Spins

Collin M. Trail, Ivan Deutsch, Leigh Norris +2 more

Chao Kong, Xiaobing Luo, Hao Chen +2 more

It has been demonstrated that the presence of chaos may lead to greater entanglement generation for some physical systems. Here, we find different effects of chaos on the spin-motion entanglement for a two-frequency driven Bose-Einstein condensate with spin-orbit coupling. We analytically and numerically demonstrate that classical chaos can assist or suppress entanglement generation, depending on the initial phase differences between two motional states, which can be manipulated by using the known phase-engineering method. The results could be significant in engineering nonlinear dynamics for quantum information processing with many-body entanglement.

Marcel Novaes

Chen-Rong Liu, Pei Yu, Xianzhang Chen +3 more

For a quantum system with multiple degrees of freedom or subspaces, loss of coherence in a certain subspace is intimately related to the enhancement of entanglement between this subspace and another one. We investigate intra-particle entanglement in two-dimensional mesoscopic systems, where an electron has both spin and orbital degrees of freedom and the interaction between them is enabled by Rashba type of spin–orbit coupling. The geometric shape of the scattering region can be adjusted to produce a continuous spectrum of classical dynamics with different degree of chaos. Focusing on the spin degree of freedom in the weak spin–orbit coupling regime, we find that classical chaos can significantly enhance spin–orbit entanglement at the expense of spin coherence. Our finding that classical chaos can be beneficial to intra-particle entanglement may have potential applications such as enhancing the bandwidth of quantum communications.

Giuliano Benenti

Chao Kong, Hao Chen, Chunlai Li +1 more

We study the spatially chaoticity-dependent spin-motion entanglement of a spin-orbit (SO) coupled Bose-Einstein condensate with a source of ultracold atoms held in an optical superlattice. In the case of phase synchronization, we analytically demonstrate that (a) the SO coupling (SOC) leads to the generation of spin-motion entanglement; (b) the area of the high-chaoticity parameter region inversely relates to the SOC strength which renormalizes the chemical potential; and (c) the high-chaoticity is associated with the lower chemical potential and the larger ratio of the short-lattice depth to the longer-lattice depth. Then, we numerically generate the Poincaré sections to pinpoint that the chaos probability is enhanced with the decrease in the SOC strength and/or the spin-dependent current components. The existence of chaos is confirmed by computing the corresponding largest Lyapunov exponents. For an appropriate lattice depth ratio, the complete stop of one of (or both) the current components is related to the full chaoticity. The results mean that the weak SOC and/or the small current components can enhance the chaoticity. Based on the insensitivity of chaos probability to initial conditions, we propose a feasible scheme to manipulate the ensemble of chaotic spin-motion entangled states, which may be useful in coherent atom optics with chaotic atom transport.