Andreev and Majorana Weyl crossings in multi-terminal Josephson junctions

We analyze the Andreev spectrum in a four-terminal Josephson junction between topological superconductors. We find that a topologically protected crossing in the space of three superconducting phase differences can occur between the two Andreev bound states with lower energy. We discuss the possible detection of this crossing through the transconductance quantization, in units of 2e^2/h, between two voltage-biased terminals. Our prediction provides another example of topology in multi-terminal Josephson junctions.