I apologize for any confusion caused by the wording in my previous response. Allow me to clarify the concept regarding the treatment of time and position in quantum field theory (QFT).
In quantum mechanics, position and time are both treated as operators. However, in the framework of QFT, there is a shift in perspective when it comes to the interpretation of these operators. Instead of promoting time to an operator, as is done in quantum mechanics, the emphasis in QFT is on the fields and their excitations, rather than individual particle positions.
In QFT, fields are operators that exist at every point in spacetime, and the excitations of these fields correspond to particles. The field operators in QFT act on a state to create or annihilate particles. These fields and their excitations are what the theory focuses on, rather than individual particle positions.
Regarding the concept of position not having a single defined value prior to measurement, that is indeed a fundamental principle in quantum mechanics. Before a measurement is made, the particle's position is described by a probability distribution given by the wavefunction. The wavefunction provides the probabilities of finding the particle in different positions upon measurement. Only after a measurement is performed does the particle's position "collapse" into a specific value.
In the context of QFT, the focus is on the fields that describe the particles and their interactions, rather than the precise position of individual particles. The fields are operators that are associated with specific positions in spacetime, and they govern the behavior of the particles. However, the treatment of position as an operator, and the associated uncertainties, still applies at the fundamental level.
So, to clarify, both time and position are operators in quantum mechanics and QFT. However, the emphasis in QFT is on the fields and their excitations rather than individual particle positions. The uncertainty in position prior to measurement remains a fundamental aspect of quantum mechanics, including within the framework of QFT.