Austrians demonstrate quantum repeater in operation

Physicists at the University of Innsbruck in Austria have succeeded in building the main parts of a quantum repeater, i.e. node of a fully functional network that allows entanglement with a photon at the standard frequency of telecommunications networks. The solution was based on the conceptualization of theoretical physicists at the university proposed a quarter of a century ago on how to transmit quantum information over long distances by such a repeater.

Based on this repeater node, a new generation of researchers have demonstrated the transfer of quantum information via a 50-kilometre-long optical fibre, placing the quantum repeater exactly in the middle of the path. The scientists were also able to identify possible advances in design to enable transmission over 800 kilometres.

As they explain, quantum networks connect quantum processors or sensors to each other. The exchange of quantum information between the nodes of the network is carried out by photons travelling through optical waves. Over long distances, the chance of lost photons is very high. As quantum information cannot simply be copied or amplified, the researchers Hans Briegel, Wolfgang Dür, Ignacio Cirac and Peter Zoller proposed a quantum repeater project 25 years ago.

Interest in quantum repeaters has already been cited by large companies such as Amazon. “We can already accomplish something at relatively small scales, but to really have global reach, there are a few things that need to be developed. One is the quantum repeater concept, which essentially does what an optical amplifier does for classical [networks],” Antia Lamas-Linares, leader of the AWS Centre for Quantum Networks, pointed out to The Register.

The Austrian researchers’ research results have been published in Physical Review Letters. The team of scientists is part of the Quantum Internet Alliance, whose mission is to establish a global quantum Internet made in Europe, with the development of a prototype with a complete stack and the validation of all major subsystems.

Scenario of the potential quantum repeater market

The firm IQT Research has done an analysis on what the quantum repeater market value will be and who the key vendors should be at the commercial level. In the 1980s and 1990s, amplifiers turned optical networks into a high-speed communications platform, and IQT Reserach believes something similar will happen when quantum repeaters come widely to market.

Importantly, no company has yet developed a quantum repeater for commercial distribution, however a group of vendors are involved with the technology, according to IQT Research, such as Cisco, ID Quantique, Juniper, Raytheon BBN, Qunnect, Aliro, NTT, NEC, Q-Bird, Toshiba and LQUOM.

As many quantum repeater designs use quantum memory, many memory approaches have been tested, including solid-state impurities, quantum dots, trapped ions, neutral atoms, cold atomic arrays, according to IQT Research. Another approach to developing quantum repeaters uses all-optical components, which can work at room temperature but suffer from scale limitations.

In the coming years, IQT Research believes that the Chinese market for quantum repeaters will dominate, while the European market will come in a distant second. Projections also show that the US will become the leading user of quantum repeaters by 2029, assuming government industry collaboration on making quantum networks continues to grow and remains well-funded.

Quantum networks in sight

By the end of July, the city of Chattanooga, Tennessee, should establish the first commercially available quantum network in the United States. According to Bloomberg, the network, valued at US$ 4.5 million, is being developed by the company Qubitekk and will be operated by EPB, the city’s public services provider.

By 2010, Chattanooga had already become the first city in the US to offer fibre-optic internet service with a speed of one gigabit, earning it the nickname Gig City. In August 2022, the service became 25 gigabits per second, costing US$1,500 per month, according to the article.

With the new quantum network, the city aspires to boost the local economy by enabling companies and universities to develop and test new equipment and applications based on quantum technology. Chattanooga Mayor Tim Kelly recently announced the Gig City Goes Quantum initiative to prepare the city in the areas of education, jobs, and business opportunities in the emerging quantum technology sector. The goal is to engage people of all ages in more than 1,000 quantum learning activities.

The EPB expects the project to recover initial investments within five years.

Meanwhile in Spain, a cooperation of companies around theMADQuantum-CM project, plans to establish Europe’s largest quantum network. MadQCI will connect, via a metropolitan fibre-optic deployment, the data centres of universities and institutes to enable the validation of new technologies as well as the development of use cases and innovations.

In particular, the MADQuantum-CM project envisages showing how quantum security solutions can be used in Madrid’s scientific network transparently, for example, to apply quantum cryptography and communication to support future 6G networks.