Spectroscopy of electron flows with single- and two-particle emitters

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 generated by 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), because 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 multielectron pulses and for the case of stochastic electron emitters for which the appearance of an electron at the quantum point contact is probabilistic.