Realizing Topological Superconductivity Near Zero Magnetic Field
Abstract
Quantum hardware and in particular quantum bits with high coherence and low error rates are vital for success of quantum technologies and quantum computing (QC). Much progress has been made on reducing qubit errors across hardware modalities in current qubits, such as trapped ions,photons, and superconducting qubits. It is proposed that when the errors on the qubits are below a certain level, ideal quantum computation is possible by sacrificing physical qubits and encoding into a fault tolerant quantum error correction scheme. Currently there are major qubit efforts at large tech companies to control error rates below the required threshold. This poses a major challenge in terms of the number of physical qubits and the difficulty of developing decoders. A fundamentally different approach that has a rich physics and could potentially revolutionize QC is to use non-Abelian quasiparticles as the foundation of an intrinsically fault tolerant system. Such states are characterized by global properties and are therefore robust to local noise; that is, they realize an error correcting code by their topological nature, without any additional overhead. The experimental study of topological phases of matter is a nascent, albeit burgeoning, field, and to leverage them for useful applications will require significant advancements in our understanding of the fundamental physics which governs their behavior.Beyond their potential application in QC, these emergent non-Abelian quasiparticles, such as Majorana bound states (MBS), are fundamentally important as they are neither Fermions, nor Bosons. Instead, exchanging Mgrees of freedom to implement fault-tolerant topological QC. Despiteimpressive experimental progress in fabricating one-dimensional (1D) structures to realize MBS these architectures are inherently limited. In 1D the evidence of MBS detection is indirect, relying on zero-bias conductance peak, rather than probing directly their non-Abelian statistics. The existing 1D geometries also pose additional obstacles to realize braiding and fusing of MBS, the key elements for topological QC. Another major obstacle is the need for an external magnetic field and its particular alignment with the nanowires.Although 1D approach is promising, our proposal takes a new path to create and manipulate topological excitations on a new 2D platform for MBS. It presents proximity-induced superconductivity in a 2D electron gas (2DEG) with phase manipulation to eliminate the need for external magnetic field and provide a more practical access to these states for future quantum circuits. With appropriate superconducting phase bias, we engineer an effective Hamiltonian in the 2DEG that supports the creation of MBS. Thus, our 2D geometry overcomes obstacles in 1D of MBS braiding and fusion, opening a new path to topological QC.Our vision for this proposal is to pursue a dual-track research program. On the one hand, we would like to understand and optimize novel epitaxial superconductor-semiconductor materials stack to control and stabilize MBSs in Josephson junctions. This requires the state-of-the-art synthesis andnanofabrication. On the other hand, we would like to investigate MBSs realization in near zero magnetic field and probe their stability under weak magnetic field regime or complete absence of external field. This requires highly precise measurements at cryogenic temperatures. The success of the program will establish not only a deeper understanding of the ingredients for MBSs inabsence of external magnetic field but also to explore their stabilities to various device parameters.Approved for Public Release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112450
Entities
People
- Javad Shabani
Organizations
- New York University
- Office of Naval Research
- United States Navy