Microfabricated ion trap chip with in situ radio-frequency sensing

Apparatus comprising an ion trap chip of the kind in which a radio-frequency (RF) surface ion trap including an RF electrode is disposed on a substrate having a plurality of metallization levels including a top metallization level N, N a positive integer, wherein:

• the ion trap chip further comprises a capacitive voltage divider integrated on the ion trap chip;
• the capacitive voltage divider includes a sensor plate, wherein the sensor plate is sandwiched between and parallel to at least a portion of the RF electrode and at least a portion of a ground plane electrode situated at a lower metallization level than the RF electrode and sensor plate, capacitively connected between the RF electrode and said ground plane electrode, and situated on at least a first metallization level lower than the top metallization level;
• the ion trap chip further comprises a sensor output trace connected to the sensor plate, formed at least in part in a different metallization layer than the first metallization layer, and adapted for conveying an RF voltage signal from the sensor plate to a connection to off-chip sensing circuitry;
• the sensor plate is coupled through a first capacitance to the RF electrode and through a second capacitance to the ground plane electrode;
• and
• the first capacitance is less than the second capacitance.