  Quantum entanglement and quantum squeezing are two most typical approaches to
beat the standard quantum limit (SQL) of the sensitive phase estimations in
quantum metrology. Each of them has already been utilized individually to
improve the sensitivity of electric field sensing with the trapped ion
platform, but the upper bound of the demonstrated sensitivity gain is very
limited, i.e., the experimental 3dB and theoretical 6dB, over the SQL. Here, by
simultaneously using the internal (spin)-external (oscillator) state
entanglements and the oscillator squeezings to effectively amplify the
accumulation phase, we show that these sensitivity gains can be effectively
surpassed. Hopefully, the proposal provides a novel approach to the stronger
beaten of the SQL for the sensitive sensings of the desired electric field and
also the other metrologies.
