Measurement of time of arrival in quantum mechanics, Y. Aharonov, J. Oppenhiem, S. Popescu, B.Reznic and W.G. Unruh, Physical Review A, Volume 57, Number 6 (1998)
It is argued that the time of arrival cannot be precisely defined and measured in quantum mechanics. By constructing explicit toy models of a measurement, we show that for a free particle it cannot be measured more accurately then DtA ~ 1/EA , where EA is the inertial kinetic energy of the particle. With a better accuracy particles reflect off the measuring device. and the resulting probability distribution becomes distorted. It is shown that a time-of-arrival operator cannot exist, and that approximate time-of-arrival operators do not correspond to measurements considered here.