Hoang T M, Anquez M, Robbins B A, Yang X Y, Land B J, Hamley C D, Chapman M S
School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
Nat Commun. 2016 Apr 5;7:11233. doi: 10.1038/ncomms11233.
Atomic spins are usually manipulated using radio frequency or microwave fields to excite Rabi oscillations between different spin states. These are single-particle quantum control techniques that perform ideally with individual particles or non-interacting ensembles. In many-body systems, inter-particle interactions are unavoidable; however, interactions can be used to realize new control schemes unique to interacting systems. Here we demonstrate a many-body control scheme to coherently excite and control the quantum spin states of an atomic Bose gas that realizes parametric excitation of many-body collective spin states by time varying the relative strength of the Zeeman and spin-dependent collisional interaction energies at multiples of the natural frequency of the system. Although parametric excitation of a classical system is ineffective from the ground state, we show that in our experiment, parametric excitation from the quantum ground state leads to the generation of quantum squeezed states.
原子自旋通常通过射频或微波场来操纵，以激发不同自旋态之间的拉比振荡。这些是单粒子量子控制技术，在单个粒子或非相互作用的系综中表现理想。在多体系统中，粒子间相互作用不可避免；然而，相互作用可用于实现相互作用系统特有的新控制方案。在此，我们展示了一种多体控制方案，用于相干激发和控制原子玻色气体的量子自旋态，该方案通过在系统自然频率的倍数下随时间改变塞曼能与自旋相关碰撞相互作用能的相对强度，实现多体集体自旋态的参量激发。尽管经典系统从基态进行参量激发是无效的，但我们表明在我们的实验中，从量子基态进行参量激发会导致量子压缩态的产生。
