An apparatus for exciting motional states of trapped ions comprising a laser unit configured to emit a first laser beam and a second laser beam , the first laser beam having a first frequency and the second laser beam having a second frequency, the first frequency being different from the second frequency; an objective configured to focus the first laser beam and the second laser beam at a position of the trapped ion , wherein the first laser beam and the second laser beam pass through at least one common lens within the objective ; and a controller configured to control said laser unit to generate a moving standing wave at the position of the trapped ion , which induces a force on the trapped ion , using the first laser beam and the second laser beam , wherein the trapped ion is a first trapped ion , and a second trapped ion is located in a focal plane of the objective , and the first and the second trapped ion are located on a trap axis, the laser unit is further configured to emit a third laser beam and a fourth laser beam , the third laser beam having a third frequency and the fourth laser beam having a fourth frequency, the third frequency being different from the fourth frequency; wherein the third laser beam and the fourth laser beam pass through the at least one common lens within the objective ; and the controller further configured to control said laser unit to induce a force on the second trapped ion using the third laser beam and the fourth laser beam , the controller is further configured to control said laser unit to simultaneously induce the force on the first trapped ion using the first laser beam and the second laser beam and the force on the second trapped ion using the third laser beam and the fourth laser beam . a laser unit configured to emit a first laser beam and a second laser beam , the first laser beam having a first frequency and the second laser beam having a second frequency, the first frequency being different from the second frequency; an objective configured to focus the first laser beam and the second laser beam at a position of the trapped ion , wherein the first laser beam and the second laser beam pass through at least one common lens within the objective ; and a controller configured to control said laser unit to generate a moving standing wave at the position of the trapped ion , which induces a force on the trapped ion , using the first laser beam and the second laser beam , wherein the trapped ion is a first trapped ion , and a second trapped ion is located in a focal plane of the objective , and the first and the second trapped ion are located on a trap axis, the laser unit is further configured to emit a third laser beam and a fourth laser beam , the third laser beam having a third frequency and the fourth laser beam having a fourth frequency, the third frequency being different from the fourth frequency; wherein the third laser beam and the fourth laser beam pass through the at least one common lens within the objective ; and the controller further configured to control said laser unit to induce a force on the second trapped ion using the third laser beam and the fourth laser beam , the controller is further configured to control said laser unit to simultaneously induce the force on the first trapped ion using the first laser beam and the second laser beam and the force on the second trapped ion using the third laser beam and the fourth laser beam . <EOS>