Electrical & computer engineering professor Eric Chitambar and physics professor Jacob Covey are bringing their quantum knowhow to InterQnet, a three-year initiative to demonstrate that quantum computers separated by large distances and even based on different hardware architectures can work in tandem. By leveraging their expertise in quantum protocols and neutral-atom quantum computing, respectively, they and their research groups will help solve important problems in the realization of such “distributed quantum computers.”
“Many researchers believe that one promising route to have fully capable quantum computers is to distribute computation between smaller ‘nodes’ that are linked together over a network,” Chitambar explained. “InterQnet is an all-hands effort, bringing together theorists, experimentalists and hardware specialists to show that this can happen.”
Quantum computers exploit the laws of quantum mechanics to perform calculations and simulations. This allows them to solve problems that are difficult or impossible to address with the methods of “classical” computing. While the principles of this new technology have been demonstrated on small and even intermediate scales, it is still uncertain how it will be realized on scales large enough to perform the most powerful calculations.
The InterQnet initiative – sponsored by the U.S. Department of Energy Advanced Scientific Computing Research program and led by Argonne National Laboratory – will give a proof of principle for the distributed quantum computing paradigm by connecting three nodes over a quantum network.
Distributed quantum computers will likely need to link different architectures to be useful since several candidates for hardware are being considered. The InterQnet network will show this is possible by connecting a superconducting qubit system to a neutral ytterbium atom array via a repeater node – a station to compensate for noise and loss as quantum information is transmitted over the network.
Covey’s group specializes in quantum computing with neutral ytterbium atoms, uniquely positioning the group to advise on the implementation and linking of this system at Argonne. “The ytterbium platform is emerging as a very promising route to distributed quantum computing, and my group is leading the charge for its use in quantum networks,” he said. “Our role is to help with the transfer of knowledge and technical skills to the Argonne group, so their ytterbium platform is in the right state to do network tasks.”
Chitambar is a theorist interested in both the structure of quantum networks and correcting for error and noise in network protocols. His group will investigate the interactions between quantum information and classical signals in the network connecting the computing nodes. “Quantum technologies will likely need to take advantage of existing telecom networks, which will support the co-propagation of both quantum and classical signals,” he said. “My group is using numerical methods to investigate correlations between these signals. Depending on the degree of correlation, it might then be possible to infer how a noisy quantum signal is propagating based on the measured behavior of the classical signal. One could then try to reverse some of the quantum noise without directly measuring it.”
InterQnet is a unique initiative, directly bringing theorists and experimentalists together to address the challenge. “The effort has prompted discussions between theory and experiment communities,” Chitambar said. “The term ‘codesign’ is used in computer science and engineering to refer to the development of software and hardware intended to work together, and we’re doing the equivalent of that here.”
