INTERVIEW: E&T MAGAZINE – ‘We need to think out of the box’: physicist Maria Spiropulu on how to build the quantum internet

Experimental physicist Maria Spiropulu is working on building the quantum internet, which could revolutionise finance, cyber security, defence and many other sectors.

Computers and the internet have revolutionised our lives, having both a profoundly positive but also, oftentimes, negative impact on society. Yet, it’s impossible to imagine life today without the World Wide Web.

And nearly 30 years after its creation, as the limits of Moore’s Law – which estimates that chip capacity doubles every two years – gets closer, companies, governments and experts are beginning to consider the next technological leap – the quantum internet.

“When we talk about the quantum internet today, it is a very loaded term,” says experimental particle physicist Maria Spiropulu, who is the Shang-Yi Ch’en Professor of Physics at the California Institute of Technology. “As a theoretical concept it is very beautiful; however, in practice, we don’t yet have all the components needed to build it.”

Spiropulu has previously worked for 10 years on the Tevatron’s collider experiments and 15 years at Cern, The European Organization for Nuclear Research, on the Large Hadron Collider (LHC).

Now, the award-wining physicist, alongside her day job working on high-energy physics and the LHC, is leading a collaborative effort to develop all the technologies needed for the future quantum internet.

In 2017, she began building the Alliance for Quantum Technologies (AQT), a novel consortium of academic and research institutions, and directing INQNET – INtelligent Quantum NEtworks & Technologies programme, which has hubs at both Caltech and the AT&T Palo Alto Foundry. The programme is seed-funded by AT&T and in September was awarded government money through the US Department of Energy’s $218m investment in quantum technologies.

Spiropulu says she wants AQT to be the “Cern of quantum technologies” with INQNET being a set of projects and experiments that will facilitate the quantum internet.

“This is not a small project; we need to build everything that is in the normal internet: quantum switches, routers, package switching – basically a parallel infrastructure that can sustain, over long periods of time and distance, what I call the beam of quantum entanglement,” she says.

Quantum entanglement is a quantum-mechanical phenomenon in which the quantum states of two or more objects, including information, are intimately correlated and connected even though the individual objects may be spatially separated.

Distributing information via quantum entanglement is considered the Holy Grail because it is inherently secure. If someone tries to intercept the information, it is instantly lost or broken.

However, while distribution of quantum entanglement is happening in small-scale lab experiments, it has not been scaled because coherent distribution is notoriously difficult to achieve at long distances. As is creating high production and detection rates of quantum entanglement.

Last year, Chinese researchers conducted a point-to-point demonstration of distributing quantum keys (quantum information) using a satellite trusted relay with optical ground links, for a 75-minute quantum-encrypted video conference call between Asia and Europe, at a distance of 7,600km. They also demonstrated the distribution of two entangled photons from a satellite to two ground stations 1,203km apart and observed the survival of entanglement, which is now considered the baseline to beat, says Spiropulu.

Due to their highly sensitive state, to distribute quantum entanglement it is necessary to either store the signal, rebroadcast it, or amplify it with precision quantum repeaters and quantum memories.

At FQNET, the Fermilab Quantum NETwork hosted at Fermilab, a National Accelerator Laboratory, with contributions from Caltech and the Jet Propulsion Laboratory (JPL), Spiropulu and her team have built a local three-node teleportation test bed to transmit entangled quantum information.

A node is a quantum location that can generate, receive or process quantum information. “It’s not exactly a mini quantum computer but a mini quantum information handler or processor,” says Spiropulu.

In 2019, the researchers aim to build another three nodes that are kilometres apart, eventually expanding to distances of tens of hundreds of kilometres, with intermediate stations and nodes between that host complex quantum devices such as repeaters and memories.

“What we want is ground to ground, ground to air and air to ground systems, and this requires integration and lots of research and development and, collaboratively, we hope to have some demonstrations in all these areas within the next two to five years,” she says.