  I propose a method to directly measure the space and time dependence of the
pair field correlator of a pair density wave. The method is based on two
separate ideas. First, we adopt the solenoid insertion method of Kapon et al
(2017) to provide the momentum in a tunnel junction. Second, we suggest the use
of optimal or over-doped Bi-2201 films as a tunneling electrode with a known
charge ordering wave-vector which can match the expected pair density wave
wave-vectors we wish to study. The method is applicable to both fluctuating and
ordered states. Potential applications are to the proposed stripe pair density
wave order in LBCO and the possible pair density wave fluctuations at finite
temperature or in high magnetic field in underdoped YBCO as well as other
members of the Cuprate family.
