March 2, 2021
A quantum internet is closer to reality, thanks to this switch
Note to journalists: For a copy of the paper, please contact Kayla Wiles, Purdue News Service, at firstname.lastname@example.org or 765-494-2432. A higher-resolution diagram of the study’s network testbed is available via Google Drive. Journalists visiting campus should follow visitor health guidelines.
New approach could help quantum networks to support more users without losing data
WEST LAFAYETTE, Ind. — When quantum computers become more powerful and widespread, they will need a robust quantum internet to communicate.
Purdue University engineers have addressed an issue barring the development of quantum networks that are big enough to reliably support more than a handful of users.
The method, demonstrated in a paper published in Optica, could help lay the groundwork for when a large number of quantum computers, quantum sensors and other quantum technology are ready to go online and communicate with each other.
The team deployed a programmable switch to adjust how much data goes to each user by selecting and redirecting wavelengths of light carrying the different data channels, making it possible to increase the number of users without adding to photon loss as the network gets bigger.
If photons are lost, quantum information is lost – a problem that tends to happen the farther photons have to travel through fiber optic networks.
“We show a way to do wavelength routing with just one piece of equipment – a wavelength-selective switch – to, in principle, build a network of 12 to 20 users, maybe even more,” said Andrew Weiner, Purdue’s Scifres Family Distinguished Professor of Electrical and Computer Engineering. “Previous approaches have required physically interchanging dozens of fixed optical filters tuned to individual wavelengths, which made the ability to adjust connections between users not practically viable and photon loss more likely.”
Instead of needing to add these filters each time that a new user joins the network, engineers could just program the wavelength-selective switch to direct data-carrying wavelengths over to each new user – reducing operational and maintenance costs as well as making a quantum internet more efficient.
The wavelength-selective switch also can be programmed to adjust bandwidth according to a user’s needs, which has not been possible with fixed optical filters. Some users may be using applications that require more bandwidth than others, similarly to how watching shows through a web-based streaming service uses more bandwidth than sending an email.
For a quantum internet, forming connections between users and adjusting bandwidth means distributing entanglement, the ability of photons to maintain a fixed quantum mechanical relationship with one another no matter how far apart they may be to connect users in a network. Entanglement plays a key role in quantum computing and quantum information processing.
“When people talk about a quantum internet, it’s this idea of generating entanglement remotely between two different stations, such as between quantum computers,” said Navin Lingaraju, a Purdue Ph.D. student in electrical and computer engineering. “Our method changes the rate at which entangled photons are shared between different users. These entangled photons might be used as a resource to entangle quantum computers or quantum sensors at the two different stations.”
Purdue researchers performed the study in collaboration with Joseph Lukens, a research scientist at Oak Ridge National Laboratory. The wavelength-selective switch that the team deployed is based on similar technology used for adjusting bandwidth for today’s classical communication.
The switch also is capable of using a “flex grid,” like classical lightwave communications now uses, to partition bandwidth to users at a variety of wavelengths and locations rather than being restricted to a series of fixed wavelengths, each of which would have a fixed bandwidth or information carrying capacity at fixed locations.
“For the first time, we are trying to take something sort of inspired by these classical communications concepts using comparable equipment to point out the potential advantages it has for quantum networks,” Weiner said.
The team is working on building larger networks using the wavelength-selective switch. The work was funded by the U.S. Department of Energy, the National Science Foundation and Oak Ridge National Laboratory.
About Purdue University
Purdue University is a top public research institution developing practical solutions to today’s toughest challenges. Ranked the No. 5 Most Innovative University in the United States by U.S. News & World Report, Purdue delivers world-changing research and out-of-this-world discovery. Committed to hands-on and online, real-world learning, Purdue offers a transformative education to all. Committed to affordability and accessibility, Purdue has frozen tuition and most fees at 2012-13 levels, enabling more students than ever to graduate debt-free. See how Purdue never stops in the persistent pursuit of the next giant leap at https://purdue.edu/.
Writer, Media contact: Kayla Wiles, 765-494-2432, email@example.com
Sources: Andrew Weiner, firstname.lastname@example.org
Navin Lingaraju, email@example.com
Journalists visiting campus: Journalists should follow Protect Purdue protocols and the following guidelines:
- Campus is open, but the number of people in spaces may be limited. We will be as accommodating as possible, but you may be asked to step out or report from another location.
- To enable access, particularly to campus buildings, we recommend you contact the Purdue News Service media contact listed on the release to let them know the nature of the visit and where you will be visiting. A News Service representative can facilitate safe access and may escort you on campus.
- Correctly wear face masks inside any campus building, and correctly wear face masks outdoors when social distancing of at least six feet is not possible.
Adaptive bandwidth management for entanglement distribution in quantum networks
Navin B. Lingaraju, Hsuan-Hao Lu, Suparna Seshadri, Daniel E. Leaird, Andrew M. Weiner, Joseph M. Lukens
Flexible-grid wavelength-division multiplexing is a powerful tool in lightwave communications for maximizing spectral efficiency. In the emerging field of quantum networking, the need for effective resource provisioning is particularly acute, given the generally lower power levels, higher sensitivity to loss, and inapplicability of optical detection and retransmission. In this Letter, we leverage flex-grid technology to demonstrate reconfigurable distribution of quantum entanglement in a four-user tabletop network. By adaptively partitioning bandwidth with a single wavelength-selective switch, we successfully equalize two-party coincidence rates that initially differ by over two orders of magnitude. Our scalable approach introduces loss that is fixed with the number of users, offering a practical path for the establishment and management of quality-of service guarantees in large quantum networks.