Still from quantum interferometers video showing researchers demonstrating how interferometers work

The quantum future of telescopes

Researchers from Quantum City partner, the Quantum Communications Hub, have recently published new work which could enable us to gain an improved understanding of the universe, using Quantum Technologies. The work, published by Cosmo Lupo, Zixin Huang and Pieter Kok, outlines the best possible method for constructing a quantum interferometer which could be incorporated into telescopes used by astronomers to study far away galaxies. The researchers, who are based at the University of Sheffield, have released a video (see below) describing the interferometer they have designed and explaining why it is superior to classical technologies.

We caught up with lead investigator Pieter recently to find out a little more about the implications and applications of this work and what it will mean for our understanding of the Universe.

So, first off, what is interferometry?

When you have a pond and you drop 2 stones in it, you get 2 sets of ripples in it, the waves of these ripples overlap producing new patterns, this is what we call interference. Light does the same thing, except at much smaller wavelengths. When you have two light waves travelling in straight lines, eventually they meet and interfere, just like water waves do. Interferometry is the experimental technique that we use to make this interference accessible, and it enable us to extract information about the light sources (such as stars) from the interference.

The video mentions that you have found the optimal way to construct a quantum interferometer which measures between two objects which are far away from us but are very close one another, giving a higher resolution than would have been able to be achieved classically. What are the implications of this in terms of our understanding of the universe?

For galaxies such as Andromeda, which is 2,000,000 light years away and considered close, you can see individual stars (with a large enough image produced by a telescope), however, if you consider trying to look at two stars which are close to one another in a distant galaxy, with a regular telescope, you can't really tell them apart, you basically just see a fuzzy ball. Being able to distinguish between stars in faraway galaxies is particularly useful because when you look at galaxies further away, you are also looking further back in time. By having technologies with a higher resolution, which enable us to see stars in distant galaxies in more detail, we will be able to see if things were the same in the distant past as they are now. We assume that this is the case, however, when we assume things and then look carefully at them, often we can find that the situation is more complicated and interesting than we assumed and therefore understanding and theories change. Ultimately, what we want to create is a coherent picture of what the universe is like, how it started, and so any observations that can offer new information on this are incredibly useful. Even the smallest piece of new information may change our understanding dramatically and therefore overturn the way we view the universe. If the interferometer that we have designed is incorporated into telescopes, their resolution would be much improved and would therefore help to give a better understanding of the universe.

What are the other applications of these quantum interferometers?

So, our work focused on the best possible way to measure the distance between objects which are very far away but very close together, however, the interferometer we designed can be used for sources at any distance, not just across the universe and this could have implications for communications. Ultimately, because our interferometer is so precise, it could enable larger amounts of information to be packed into a communications signal than is currently possible, for example, and it still be detected. This could lead to communications devices being able to be smaller because they can transmit signals containing more information, on a smaller scale.

Your colleague Zixin mentions that quantum imaging technologies which use methods like yours could be commercialised soon, when do you think this will be?

I think it is actually quite close. Zixin and I are currently working with experimental colleagues in Germany to see when our techniques would be most useful in astronomy, and we are working with astronomers to see how our technologies could be integrated within their current telescopes. If this is possible, our interferometers could be in use very quickly, within a year or two even.

What is next for your work in this area?

We have reached the limit of resolution for this technology, it can’t get any better than this, however, we are looking at how we can increase the distance that these interferometers can be separated by and still provide useful data. By having the interferometers really spread out they could act like a huge telescope and will enable high resolution imaging of galaxies even further away, giving insight into the universe even further back in time. Usually, when the interferometers are separated by over 100m it is difficult to obtain coherent signals, and if you put the light through optical fibres, you can lose some of it. Repeaters can be used to repeat the signal before it is lost, but this is not ideal and can still pose issues. We are investigating how we could overcome these issues by building networks of interferometers and ideally, we’d like to surround the globe with a network of these technologies. We have been working on this and the longest distance I think we achieved was approximately 2000km, extending beyond this is an enormous technological challenge but is something we are working on.

The networks we hope to build could also be used as a platform for secure communications and potentially to connect multiple quantum computers across large distances, therefore enabling the quantum internet.

Are there any other areas of quantum technologies that you’re excited about, and if, so why?

I’m really excited about the quantum computing side of things. People around the world are working very, very hard on this and are running incredible experiments. There are a number of technologies that are being developed that could make up the final form of the technology, whether that is superconducting qubits, ion traps or solid-state qubits with optical interfaces, for example. A lot of work is going on to make these technologies scalable and also to develop ways of linking multiple quantum computers up to create a quantum internet. It’s hard to know which technology will end up being the final form of a quantum computer, but we will learn a lot of physics along the way, and the impact on society will be tremendous.