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.”
While an interesting approach, the cost of refrigeration equipment is somewhat ignored in a wavelength-selective switch. Creating a quantum internet is potentially feasible, however, the cost is not addressed here, just the technology. Quantum computer services do seem feasible, where the investment can exceed several $B. Commercial companies could take advantage of such a service. Quantum internet is another concept that needs to consider the investment, especially temperatures near -460 degrees F. China has created a photon-based quantum computer that is less sensitive to low temperatures, such that the energy to needed to flip a quantum spin-state is less sensitive to temperature and noise considerations. More research is needed for a quantum internet to make it notably secure with variable bandwidth; but cost effective for all internet users.
Web Reference : https://www.sciencedaily.com/releases/2021/03/210302154236.htm