  To analyze the state of injected carrier streams of different electron
sources, we propose to use correlation measurements at a quantum point contact
with the different sources connected via chiral edge states to the two inputs.
In particular we consider the case of an on-demand single-electron emitter
correlated with the carriers incident from a biased normal reservoir, a contact
subject to an alternating voltage and a stochastic single electron emitter. The
correlation can be viewed as a spectroscopic tool to compare the states of
injected particles of different sources. If at the quantum point contact the
amplitude profiles of electrons overlap, the noise correlation is suppressed.
In the absence of an overlap the noise is roughly the sum of the noise powers
due to the electron streams in each input. We show that the electron state
emitted from a (dc or ac) biased metallic contact is different from a
Lorentzian amplitude electron state emitted by the single electron emitter (a
quantum capacitor driven with slow harmonic potential), since with these inputs
the noise correlation is not suppressed. In contrast, if quantized voltage
pulses are applied to a metallic contact instead of a dc (ac) bias then the
noise can be suppressed. We find a noise suppression for multi-electron pulses
and for the case of stochastic electron emitters for which the appearance of an
electron at the quantum point contact is probabilistic.
