ML4Q Projects

Scientific Structure

The scientific structure of ML4Q is spanned by four focus areas, each addressing a specific set of problems relevant to the cluster’s mission. All focus areas include theoretical as well as experimental components and transcend the boundaries of disciplines and institution:

F1: Fundamentals and technology for topological interfaces
(coordinators: Morgenstern & Rosch)
F2: Majorana qubits (coordinators: Ando & Hassler)
F3: Decoherence, measurements, and error correction
(coordinators: DiVincenzo & Kollath)
F4: Quantum connectivity (coordinators: Bluhm & Köhl)

Within the focus areas, we have defined 12 core projects targeting sharply defined scientific questions. They will be complemented by additional open call projects to ensure the flexibility of the research program.

Core Projects

P1.1:

Interfaces between topological insulators and superconductors

Topological insulators in contact with super-conductors allow for realizing Majorana states. Improving the quality of these interfaces is decisive for the robustness of the Majorana states and resulting qubits. 

Participants

 Grützmacher (J, coordinator)
Ando (C)
Blügel (J)
Grüneis (C)
Mayer (A)
Morgenstern (A) 
Mussler (J)
Plucinski (J)
Schäpers (J)

P1.2:

Topological-insulator nanowires for Majorana states

We believe that nanowires of topological insulators in contact with superconductors are ideal building blocks for Majorana devices. We will explore different approaches to make and control such wires.

Participants

Ando (C, coordinator)
Grützmacher (J)
Lu (USC)
Mayer (A)
Morgenstern (A)
Mussler (J)
Rosch (C)
Schäpers (J)

P1.3:

Controlling and probing ultra-clean interfaces

Novel fabrication techniques in ultra-high vacuum (UHV) are required for high-quality devices. We will develop new nanostructuring techniques and methods to probe Majorana states directly in UHV.

Participants

Morgenstern (A, coordinator)
Grützmacher (J)
Mussler (J)
Stampfer (A)
Tautz (J)
Voigtländer (J)

P1.4:

Majorana states and parafermions in ultracold-atom systems

With ultracold atoms we will be able to realize and explore novel topological states and interfaces that are motivated by condensed matter systems.

Participants

Weitz (B, coordinator)
Diehl (C)
Köhl (B)
Kollath (B)
Rosch (C)

P2.1:

Majorana qubits based on topological-insulator nanowires

Majorana qubits will be built from topological-insulator nanowires and superconductors. We aim to demonstrate not only simple qubit operations but also the non-Abelian nature of Majoranas by braiding.

Participants

Ando (C, coordinator)
Altland (C)
Bluhm (A)
Egger (D)
Fink (IST Austria)
Grützmacher (J)
Hassler (A)
Lu (USC)
Mussler (J)
Schäpers (J)
Stampfer (A)

P2.2:

Alternative platforms for Majorana qubits

We will explore how superconducting vortices,
quantum anomalous Hall insulators, and graphene can be used to realize Majorana qubits.

Participants

Ando (C, coordinator)
Altland (C)
Bluhm (A)
Egger (D)
Fink (IST Austria)
Hassler (A)
Morgenstern (A)
Stampfer (A)

P2.3:

Advanced Majorana-qubit designs

With Majorana box qubits one can realize new types of codes to implement active and passive error correction tailored to this computational platform.

Participants

Hassler (A, coordinator)
Altland (C)
Ando (C)
Egger (D)

P3.1:

Topology in and out of equilibrium

Concepts of topology are combined with a microscopic description of noise and dephasing. These ideas will be explored in ultracold-atom experiments and applied to the Majorana-based designs.

Participants

Diehl (C, coordinator)
Altland (C)
DiVincenzo (A/J)
Hassler (A)
Köhl (B)
Kollath (B)

P3.2:

Theory of error character­ization, mitigation, and correction

Noise and resulting errors are the main factor limiting quantum computing devices. In this theory project, we will characterize the noise and its origins, validate devices and protocols and improve error-correction codes.

Participants

Gross (C, coordinator)
Bruss (D)
Calarco (C/J)
DiVincenzo (A/J)
Kastoryano (C)
Terhal (J)
Trebst (C)

P3.3:

Electron shuttling for spin-qubit surface code

To realize topological error correction one needs reliable building blocks connected by quantum links. We develop a quantum bus to shuttle spin qubits over micron-scale distances. This will be used to make and test connected arrays of spin qubits for error-correcting surface codes.

Participants

Bluhm (A, coordinator)
DiVincenzo (A/J)
Knoch (A)
Schreiber (A)

P4.1:

Multipartite quantum networks

What type of novel quantum protocols can be used on quantum networks involving several nodes? We will study this question theoretically and will realize in experiments a novel source of entangled photons that can be distributed to multiple nodes.

Participants

Bruss (D, coordinator)
Gross (C)
Grützmacher (J)
Kroha (B)
Weitz (B)

P4.2:

Quantum links

We expect that future quantum technologies will build on networks linking solid-state qubits to flying qubits made from light. We will coherently couple a spin qubit to light, use this to build a heterogeneous network involving spin qubits and trapped ions, and couple Majorana states to microwave photons.

Participants

Bluhm (A)
Ando (C)
Fink (IST Austria)
Kardynal (J)
Köhl (B)
Linden (B)
Meschede (B)
Pawlis (J)
Stampfer (A)
Stellmer (B)