Increasing the storage time of quantum information in semiconductor nanostructures.

Left: Armando Rastelli, Christian Schimpf and Saimon Covre da Silva; Credit: JKU
Left: Armando Rastelli, Christian Schimpf and Saimon Covre da Silva; Credit: JKU

Countries and corporations around the world are researching a completely new type of computer - quantum computers. But the road to usability is arduous. Researchers at Johannes Kepler University Linz have succeeded in making progress in the storage of quantum information as part of an international collaboration.

Semiconductor-based nanostructures are one thing above all: tiny. They are on the order of less than 50 nanometers. By comparison, viruses are up to 400 nanometers "big. Semiconductor structures are already used in memory cards to store classical data - but not yet in quantum computers.

Semiconductor-based nanostructures can also be used as sources of quantum information (Qbits) - a task they perform excellently. But quantum information must also be stored, for example in the spin of a single electron - and semiconductor-based nanostructures fulfill this function very modestly.

Because: ,,Quantum information is very short-lived, which is caused by interactions of electrons and the noise of atomic nuclei," explains Univ. Prof. Armando Rastelli, who heads the Department of Semiconductor Physics at JKU.

JKU clean room at the LIT Open Innovation Center enables progress.
Unconventional and electrically controllable nanostructures have now led to success: Unlike previous attempts, individual electron spins were fixed as quantum information in stress-free nanostructures made of gallium arsenide. These samples were fabricated in the clean room at JKU.

The result: The storage time of quantum information (Qbits) was extended by a factor of 100! In absolute numbers it shows that the applicability is still far away: The information was stored for only 0.1 milliseconds.My team with Santanu Manna, Saimon Covre da Silva and Christian Schimpf has shown, however, that with the right choice of materials and approach, semiconductor nanostructures do have potential," says Rastelli.

The experiments were carried out together with scientists from the Universities of Cambridge, Oxford and Sheffield and have now been published in the renowned journal "Nature Nanotechnology" under the title"Ideal refocusing of an optically active spin qubit under strong hyperfine interactions".

This research direction is appealing, Rastelli says. Using the same choice of materials, the world’s highest degree of entanglement for photon pairs from semiconductor nanostructures was already achieved at JKU in 2018 and successfully used practically for quantum cryptography in 2021.