  Millisecond pulsars (MSPs) have been studied in detail since their discovery
in 1982. The integrated pulse profiles of MSPs appear to be stable, which
enables precision monitoring of the pulse times of arrival (TOAs). However, for
individual pulses the shape and arrival phase can vary dramatically, which is
known as pulse jitter. In this paper, we investigate the stability of
integrated pulse profiles for 5 MSPs, and estimate the amount of jitter for PSR
J0437-4715. We do not detect intrinsic profile shape variation based on
integration times from ~10 to ~100 s with the provided instrumental
sensitivity. For PSR J0437-4715 we calculate the jitter parameter to be
f_J=0.067+-0.002, and demonstrate that the result is not significantly affected
by instrumental TOA uncertainties. Jitter noise is also found to be independent
of observing frequency and bandwidth around 1.4 GHz on frequency scales of <100
MHz, which supports the idea that pulses within narrow frequency scale are
equally jittered. In addition, we point out that pulse jitter would limit TOA
calculation for the timing observations with future telescopes like the Square
Kilometre Array and the Five hundred metre Aperture Spherical Telescope. A
quantitative understanding of pulse profile stability and the contribution of
jitter would enable improved TOA calculations, which are essential for the
ongoing endeavours in pulsar timing, such as the detection of the stochastic
gravitational wave background.
