The upper optical layer consists of two orthogonal pairs of cleaved single-mode optical fibres. One of the pairs (along y ) creates a standing wave at y = 1,550 nm, while the second pair (along x ) creates a standing wave at x = 1,064 nm. The distances between the fibres are d x = 80 m and d y = 160 m. A particle (black) is trapped at the intersection of both standing waves. The light scattered by the particle into the fibres, represented by the arrows, is used for displacement detection. The four fibres are positioned above a set of planar electrodes used to apply active feedback cooling to the charged particle via electric forces: right and left electrodes for feedback along x , top and bottom for feedback along y , and centre electrode for feedback along z.
