Researchers store a quantum bit for a record-breaking 20 milliseconds

Many technological advances have been enabled by quantum physics. It is opening up new fields of research in order to develop ultra-secure telecommunications networks. After a few hundred kilometers within an optical fiber, the photons that carry the qubits or quantum bits disappear. They needrepeaters, which are partly based on a quantum memory. A team from the University of Geneva has set a world record by storing a qubit in a crystal for 20 milliseconds. This research can be found in the journal.

Scientists have been able to describe the behavior of atoms and particles with the help of quantum physics. By breaking with classical physics, these theories generated a real revolution and introduced notions without equivalent in the macroscopic world such as superposition, which describes the possibility for a particle to be in several places at once.

There is a lot of research into quantum theories in the field of cryptanalysis. It is possible to guarantee perfect authenticity and confidentiality for information when it is transmitted between two people by a photon within an optical fiber. The phenomenon of superposition lets the sender know if the photon has been intercepted.

Memorizing the signal.

There is a major obstacle to the development of long-distance quantum telecommunication systems: beyond a few hundred kilometers, the signal disappears. Since the signal cannot be copied or amplified, the challenge is to find a way of repeating it without altering it.

In 2015, a team led by a senior lecturer in the Department of Applied Physics at the Faculty of Science of the University of Geneva succeeded in storing a qubit in a crystal. The photon could transfer its quantum state to the atoms of the crystal. The construction of a larger network of memories was a precondition for the development of long-distance quantum telecommunications.

There is a storage record.

This is a world record for a quantum memory based on a solid-state system. The researcher says that they have reached the 100 millisecond mark with a small loss of fidelity. As in their previous work, the UNIGE scientists used rare earths and crystals that could absorb light and then emit it. The crystals were kept at absolute zero because the thermal oxidation of the atoms destroys them.

We applied a small magnetic field of one thousandth of aTesla to the crystal and used dynamic decoupling methods, which send intense radio frequencies to the crystal. The effect of these techniques is to decouple the rare-earth ion from the environment and increase the storage performance we have known until now by almost a factor of 40. The results of this research show a major advance in the development of long-distance quantum telecommunications networks. The storage of a quantum state carried by a photon can be estimated by humans.

An efficient system for a decade.

The challenge now is to extend the storage time further. In theory, it would be enough to increase the exposure of the crystal to radio frequencies, but for the time being, technical obstacles to their implementation over a longer period of time prevent us from going beyond 100 milliseconds. It is certain that the technical difficulties can be solved.

The aim is to develop a system that performs well on all these points.

More information: Antonio Ortu et al, Storage of photonic time-bin qubits for up to 20 ms in a rare-earth doped crystal, npj Quantum Information (2022). DOI: 10.1038/s41534-022-00541-3 Citation: Researchers store a quantum bit for a record-breaking 20 milliseconds (2022, March 22) retrieved 22 March 2022 from https://phys.org/news/2022-03-quantum-bit-fora-record-breaking-milliseconds.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.