More stable states for quantum computers
Quantum computers are considered to be the computers of the future. Quantum bits (qubits), the smallest computational unit of quantum computers, are the be-all and end-all. Because they have not only two states, but also states in between, qubits process more information in less time. However, maintaining such a state for a longer time is difficult and depends in particular on material properties. A KIT research team from the Helmholtz Research Field Information now generated qubits that are 100 times more sensitive to material defects – a crucial step toward eliminating them. The team published the results in the journal Nature Materials (DOI: 10.1038/s41563-022-01417-9). (Source: Karlsruhe Institute of Technology – Press Releases)
Quantum computers can process large amounts of data faster because they perform many computing steps in parallel. The information carrier of the quantum computer is the qubit. With qubits, there is not only the information “0” and “1”, but also values in between. At the moment, however, the difficulty lies in producing qubits that are small enough and can be switched fast enough to perform quantum calculations. Superconducting circuits are considered a promising option here. Superconductors are materials that exhibit no electrical resistance at extremely low temperatures and therefore conduct electrical current without loss. This is crucial for preserving the quantum state of qubits and connecting them efficiently.
Gralmonium Qubits: Superconducting and Sensitive
KIT researchers have succeeded in developing novel and unconventional superconducting qubits. “The heart of a superconducting qubit is a so-called Josephson junction, which is used to store quantum information. It is precisely at this point that we have made a crucial change,” says Dr. Ioan M. Pop of KIT’s Institute for Quantum Materials and Technologies (IQMT). Usually, such Josephson junctions for superconducting quantum bits are created by separating two aluminum layers with a thin oxide barrier. “In contrast, for our qubits we use only a single layer of ‘granular aluminum,’ a superconductor of aluminum grains a few nanometers in size embedded in an oxide matrix,” Pop says. As a result, the material forms a three-dimensional network of Josephson junctions on its own. “Excitingly, the entire properties of our qubit are dominated by a tiny constriction of only 20 nanometers. This makes it act like a magnifying glass for microscopic material defects in superconducting qubits and offers a promising perspective for their improvement,” adds Simon Günzler of the IQMT.
From a single mold: qubits made entirely of granular aluminum
The qubits developed by the team are a fundamental further development of a previously tested approach using so-called fluxonium qubits. In that previous version, parts were made of granular aluminum and other parts were conventionally made of aluminum. In the current work, the researchers went the extra mile and fabricated the entire qubits from granular aluminum. “It’s like simply cutting a quantum circuit out of a metal film. This opens up completely new possibilities for industrial production using etching methods and extended areas of application for the qubits, for example, in strong magnetic fields,” says Dennis Rieger of the KIT Institute of Physics.
The authors have also protected this invention by a European patent.
The original press release can be found at:
Stabilere Zustände für Quantencomputer (only in german)
The original publication can be found at:
D. Rieger, S. Günzler, M. Spiecker, P. Paluch, P. Winkel, L. Hahn, J. K. Hohmann, A. Bacher, W. Wernsdorfer, and I. M. Pop: Granular Aluminium Nanojunction Fluxonium Qubit. Nature Materials, 2022. DOI: 10.1038/s41563-022-01417-9
Localization in the Helmholtz Research Field Information:
Helmholtz Research Field Information, Program 2: Natural, Artificial and Cognitive Information Processing, Topic 2: Quantum Computing
Contact:
Dr. Ioan Pop
Institute for Quantum Materials and Technologies (IQMT)
Karlsruher Institute of Technology (KIT)
Phone: +49 721 608-43507
E-Mail: ioan.pop@kit.edu
Contact for this press release:
Sandra Wiebe
Press Officer
Karlsruher Institute of Technology (KIT)
Phone: +49 721 608-41172
E-Mail: sandra.wiebe@kit.edu
