Quantum System Theory Research Team

Principal Investigator

PI Name

Daniel Loss

Degree

Ph.D.

Title

Team Leader

Brief Resume

1985	Ph.D. in Theoretical Physics, University of Zurich, Switzerland
1985	Postdoctoral Research Associate, University of Zurich, Switzerland
1989	Postdoctoral Research Fellow, University of Illinois at Urbana-Champaign, USA
1991	Research Scientist, IBM T. J. Watson Research Center, USA
1993	Assistant/Associate Professor, Simon Fraser University, Canada
1996	Professor, Department of Physics, University of Basel, Switzerland (-present)
2012	Team Leader, Emergent Quantum System Research Team, RIKEN
2013	Team Leader, Quantum System Theory Research Team, Quantum Information Electronics Division, RIKEN Center for Emergent Matter Science (-present)

Outline

Our team is working on the quantum theory of condensed matter with a focus on spin and phase coherent phenomena in semiconducting and magnetic nanostructures. In particular, the team investigates the fundamental principles of quantum information processing in the solid state with a focus on spin qubits in quantum dots, superconducting qubits, and topological quantum states such as Majorana fermions and parafermions. This involves the study of decoherence in many-body systems and scalable quantum computing technologies based on surface codes and long-distance entanglement schemes. We also study nuclear spin phases, many-body effects in low-dimensional systems, quantum Hall effect, topological matter, spin orbit interaction, and quantum transport of magnetization.

Research Fields

Theoretical Physics, Quantum Theory of Condensed Matter

Keywords

Quantum dots
Spin-based quantum information science
RKKY interaction in low dimensions
Topological quantum matters
Majorana fermions and parafermions

Results

Majorana Kramers pairs in higher-order topological insulators

Higher order topological insulators are systems which realize the most recent flavor of topological matter. While being insulating in the bulk and on the surface, they host propagating states at the edges (hinges), where two facets meet. We designed a tune-free scheme to realize Kramers pairs of Majorana bound states in higher-order topological insulators with proximity-induced superconductivity.

Our scheme is an experimentally accessible setup, which proposes to use a bismuth wire half-covered by a superconductor. Namely, we find that when two hinges with the same helicity of the wire are in contact to an s-wave superconductor, moderate electron-electron interactions favor the inter-hinge pairing over the intra-hinge pairing, leading to formation of Majorana Kramers pairs. As a result, the proposed scheme does not require a magnetic field or local voltage gates, which is a highly desired property in the quest for topological states.

Left panel: Higher order topological insulator realized using a superconductor (yellow) and a wire (green). Right panel: The phase diagram of the model shown in the Left panel.
Chen-Hsuan Hsu, Peter Stano, Jelena Klinovaja, and Daniel Loss, “Majorana Kramers Pairs in Higher-Order Topological Insulators,” Phys. Rev. Lett. 121, 196801 (2018) © APS

Members

Daniel Loss	Team Leader	loss.daniel[at]riken.jp
Peter Stano	Senior Research Scientist	peter.stano[at]riken.jp
Chen-Hsuan Hsu	Research Scientist	chen-hsuan.hsu[at]riken.jp
Angel Gutierrez Rubio	Postdoctoral Researcher
Ognjen Malkoc	Postdoctoral Researcher