Is there a to-and fro trip Xian - Qin Shi Huang mausoleum and Terracotta warriors taxi service

I'm afraid no. Actually, you can take tourism bus 305 from the east square of XA railway station to these places directly. The buses depart every 5 minutes and are air-conditioned. It's very convenient.

If by taxi, it takes about CNY100 by meter. But most drivers would not use the meter and wouldn't like to travel that far.