  For the search of Majorana fermions, we propose to employ a ramp-type
Josephson edge junction between a normal metal such as Au, Ag or alloys of
heavy metals and a topologically-trivial dx2-y2 wave high-Tc superconductor
YBa2Cu3O7. The success in forming the elusive zero-energy Majorana bound states
(MBS) at the junction relies crucially upon the strength of the Rashba
spin-orbit coupling (RSOC) at the metal/superconductor interface, the tunneling
direction, and the interface quality which includes a near zero tunnel barrier
height. When these junction conditions are collectively satisfied, definitive
signatures of Majorana fermions will emerge. After inspecting a vast amount of
published data of junctions that are close to what we have proposed, we were
able to find: 1) angular resonant Andreev reflection, and 2) quantized zero
bias normalized differential conductance peak (ZBCP), as possible evidence for
MBS formed at the junction interface. Encouraged by these findings, we have
designed a MBS-supporting d-wave superconductor based pi-loop heterostructure
as a qubit platform. Such pi-loops are characterized by a doubly degenerate
half flux quantum vortex (HQV) and are topologically protected by a parity
effect arising from an odd number of sign changes of the supercurrent
circulating in the loop. The topological protection is further enhanced by the
formation of RSOC induced Majorana bound states at the Josephson junction
interface. The proposed MBS-plus-HQV qubit platform will be useful for
demonstrating non-Abelian exchange statistics and for building a prototype
topological quantum computer.
