As described in a news release, one of the challenges to creating a quantum network has been photon loss, or a loss of information that can happen when photons travel through fiber-optic networks. To solve this, Purdue researchers developed a programmable switch to adjust wavelengths of light that carry data to specific users on the quantum network, allowing the number of users to increase without also increasing photon loss.
Published this month in the journal Optica, the new method solves issues with entanglement, a key concept in quantum information processing, as the network grows and enables communication between several quantum computers.
“It was sort of unclear whether this [method] is something that could be deployed for entangled distribution, and that was something we were looking to address,” said Navin Lingaraju, an electrical engineering graduate student and research team member. “That’s where our work comes in, is looking at possible ways to boost the connectivity between different users."
The switch can also adjust bandwidth in a way that wasn’t previously possible with fixed optical filters, allowing engineers to direct data-carrying wavelengths to each new user. Andrew Weiner, professor of electrical and computer engineering, said this new method works in a way that’s similar to classical lightwave communications and could be used on “metropolitan scales.”
Weiner explained that the previous approach to solving photon loss involved interchanging multiple fixed optical filters - a painstaking and inefficient process.
“Quantum networks will need to distribute entanglement – strong correlations at a distance between quantum particles, which are at the heart of quantum information,” he said. "Our contribution is to introduce reprogrammable wavelength routing equipment, which means that we can reconfigure the connections under computer control ... Such programmability and flexibility could provide an early opportunity to enable network architects to perform experimentation with simple quantum mechanical network protocols.”
The team's research was funded through several grants from the U.S. Department of Energy, National Science Foundation and Oak Ridge National Laboratory. Last year, Purdue joined with other institutions' research efforts at the Quantum Science Center headquartered at Oak Ridge National Laboratory, which was awarded $115 million over five years.
Lingaraju said the study, conducted in collaboration with Oak Ridge National Laboratory research scientist Joseph Lukens, could provide an addition to the future quantum Internet toolkit.
While the widespread use of quantum technology, or whether it could be used for things like advanced artificial intelligence, remain years down the road, Lingaraju said quantum technology “captures the imagination.”
“It’s very early work in what is an ill-defined concept at the moment, which is the quantum Internet. We think it’s a solution, but there are many possible tools to use,” he said. “The idea of the quantum Internet is so early and vague that it very much is throwing stuff at a wall and seeing what sticks or waiting to see what people need five years down the road ... The general impetus is, you don’t want to wait until you have the need [before] you start doing the research.”
Weiner said he thinks quantum technology will revolutionize how we process information. He noted that long-term research on quantum devices and network architecture are still needed to make these technologies useful on a widespread scale.
“Current quantum computers are still too small to impact practical problems, and scaling up the size of individual processors is very challenging. This leads to great interest in distributed quantum computing, which would depend on the communication of quantum information between separated quantum processors,” he said. “The situation is not unlike cloud and high-performance computing, where the linking of distributed resources has led to breathtaking advances in fields like data science and artificial intelligence ... However, quantum information and classical information are very different, and research on a proposed quantum Internet, which could, for example, connect distributed quantum computers, is at a very early stage."
