1- Anti Aliasing
Antti-aliasing is a computer graphics technique that smoothes jagged edges on curves and diagonal lines. It helps to make digital images appear more realistic by eliminating the “staircase” effect that often appears on curved or angled lines.
To use antialiasing turn on antialiasing button 
, it’s located on top of viewport.
By default Maya uses 8 sample per pixel for AA, but you can change it by opening viewport options in 
on top of viewport and opening viewport2.0 window.
2-Ambient Occlusion
click on 
on top of viewport to use AO, you can change its settings in viewport options as well.
3 – denoising
The lower samples in render settings results in quick builds but noisy images, you can reduce this noise by
1 – open render settings and go to Arnold renderer tab
2 – in images section, press add imager
3 – three denoising options are available (optix-odin and nice) choose one of them
4 – color and exposer
1 – open render settings and go to Arnold renderer tab
2 – in images section, press add imager
3 – different imagers are available, look at Arnold documents to learn their usage