Wrubel J P, Schwettmann A, Fahey D P, Glassman Z, Pechkis H K, Griffin P F, Barnett R, Tiesinga E, Lett P D
Department of Physics, Creighton University, 2500 California Plaza, Omaha, Nebraska 68178, USA.
Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 W. Brooks Street, Norman, Oklahoma 73019, USA.
Phys Rev A (Coll Park). 2018;98. doi: 10.1103/PhysRevA.98.023620.
The SU(1,1) interferometer was originally conceived as a Mach-Zehnder interferometer with the beam-splitters replaced by parametric amplifiers. The parametric amplifiers produce states with correlations that result in enhanced phase sensitivity. = 1 spinor Bose-Einstein condensates (BECs) can serve as the parametric amplifiers for an atomic version of such an interferometer by collisionally producing entangled pairs of | = 1, = ±1〉 atoms. We simulate the effect of single and double-sided seeding of the inputs to the amplifier using the truncated-Wigner approximation. We find that single-sided seeding degrades the performance of the interferometer exactly at the phase the unseeded interferometer should operate the best. Double-sided seeding results in a phase-sensitive amplifier, where the maximal sensitivity is a function of the phase relationship between the input states of the amplifier. In both single and double-sided seeding we find there exists an optimal phase that achieves sensitivity beyond the standard quantum limit. Experimentally, we demonstrate a spinor phase-sensitive amplifier using a BEC of Na in an optical dipole trap. This configuration could be used as an input to such an interferometer. We are able to control the initial phase of the double-seeded amplifier, and demonstrate sensitivity to initial population fractions as small as 0.1%.
SU(1,1)干涉仪最初被设想为一种马赫-曾德尔干涉仪，其中分束器被参量放大器所取代。参量放大器产生具有相关性的态，从而导致相位灵敏度增强。自旋为1的玻色-爱因斯坦凝聚体（BECs）可以通过碰撞产生| = 1, = ±1〉原子的纠缠对，作为这种干涉仪原子版本的参量放大器。我们使用截断维格纳近似来模拟放大器输入的单边和双边注入的效果。我们发现，单边注入恰好在未注入的干涉仪应具有最佳性能的相位处降低了干涉仪的性能。双边注入会产生一个相位敏感放大器，其中最大灵敏度是放大器输入态之间相位关系的函数。在单边和双边注入中，我们都发现存在一个最优相位，可实现超越标准量子极限的灵敏度。在实验中，我们展示了一种使用光偶极阱中的钠BEC的自旋相位敏感放大器。这种配置可以用作这种干涉仪的输入。我们能够控制双注入放大器的初始相位，并展示对低至0.1%的初始粒子数分数的灵敏度。
