Using Crossed Andreev Reflection to Split Electrons

Abstract

Mesoscopic systems possess shot noise in their currents due to the quantization of the conducting quasiparticles. Measurements of this shot noise are useful to study phenomena that do not manifest themselves in standard conductance or resistance measurements, such as the statistics of the conducting quasiparticles or quantum entanglement via Bell tests. The corresponding particle statistics can be determined via two particle quantum interference experiments, such as the Hong-Ou-Mandel effect which demonstrates a bunching effect for bosons or an anti-bunching effect in fermions. In superconducting proximity junctions, electrons incident on a superconductor can induce holes via crossed Andreev reflection (CAR) in spatially separated normal metal leads, where the resulting hole currents have nontrivial partition noise due to the four terminal configuration. These nonlocally generated currents, using a superconductor as a mesoscopic beam splitter, enable fabrication of mesoscopic analogs to quantum optics interferometers using metallic and superconducting films with multiport geometries.

Figures (2)

• Figure 1: Schematic of the Hong-Ou-Mandel two-photon interference effect.
• Figure 2: Schematic of a quasiparticle beam splitter based on crossed Andreev reflection. Blue represents the superconductor while gold represents normal metal wires. The diameter of the superconducting circle is of order of the superconducting coherence length $\xi$. The superconducting line below the circle is to drain any current injected into the superconductor from leads 1 and 2, with the current from lead 1 portrayed above.