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Are you ready for the quantum internet?

Speed read
  • Enabling quantum computers to talk to each other will require upgrading the internet
  • Preserving quantum entanglement over long distances demands many new technologies
  • Center for Quantum Networks aims for fault-tolerant entanglement distribution by 2030

Quantum computers have the potential to be millions of times more powerful than today’s top-performing supercomputers at solving certain crucial problems that classical computers cannot solve. This new kind of computing, based on quantum mechanics, is predicted to revolutionize everything from medicine to banking to artificial intelligence, and more.

<strong>A quantum internet will allow quantum computers to talk to each other.</strong> Here, Linran Fan, UA assistant professor of optical sciences, works on quantum nanophotonic system design. Courtesy University of Arizona. But in order for that to happen, quantum computers are going to have to improve beyond their current experimental state, and they’re also going to have to learn how to talk to each other.

After all, we had classical computers for a long time, but the tech-saturated world we live in didn’t take off until there was widespread internet connectivity. But quantum communication presents a few new problems: 

One is that quantum bits (qubits) can’t be transmitted over the networks we have now. The other is that functional quantum computing will instantly break all of the encryption on the current internet.

So what to do? Upgrade the internet, of course.

“We’ll be upgrading the internet to be quantum capable,” says Saikat Guha, professor of optical sciences at the University of Arizona (UA) and director of the brand-new Center for Quantum Networks (CQN). A collaboration with Harvard, MIT, and Yale, the CQN has just received a $26 million grant from the National Science Foundation to prepare for the future of quantum communication.

The center strings together almost every area of quantum information science and engineering. We bring together work on sensors, communications, computers, processors, networking, materials development, memory research, entanglement, tomography, protocol design, and error correction—everything under one umbrella ~ Saikat Guha

A quantum internet will allow quantum computers and other quantum devices to communicate. Just as the current internet exchanges information between classical computers by transmitting bits, a quantum internet will transmit qubits. But as it turns out, transmitting qubits is a lot harder to do. 

The current internet relies on optical amplifiers to extend and repeat signals over long distances and across different fiber types, wavelengths, and network architectures. But when it comes to quantum communication, these optical amplifiers create enough noise to destroy quantum characteristics such as entanglement.

2023: operational quantum communication testbed
2025: fully operational quantum repeater
2030: quantum data exchanged at full quality

Enter the quantum repeater. This complex subsystem divides long communication distances into several segments and suppresses the influence of noise to relay a quantum entangled state over a longer distance with high fidelity. It does this by stitching together pairs of entangled qubits over those smaller segments into one entangled qubit pair between a pair of distant parties. A big part of CQN’s research will be concentrated on building a successful quantum repeater. 

“The big focus of our center will be to build the capability of transmitting qubits reliably from one computer to another, one processor to another,” says Guha. “And not just that—it’s going to be able to serve multiple users, multiple applications, and multiple gadgets, all on the same underlying network.” 

To begin with, an experimental quantum network testbed is currently being built on the UA campus under the leadership of Prof. Zheshen Zhang of the Material Science and Engineering department.

While there are currently no quantum computers on campus, CQN will be transitioning quantum memory technology from MIT and Harvard, and will start building quantum repeaters. Industry partners will have early access to the test bed to try out their own technology, e.g., quantum computers, communications devices, and sensors. 

“We’re going to start with communicating across nodes using quantum repeaters,” says Guha. “We’ll be measuring and characterizing the rate at which entanglement can be supplied between end-to-end nodes, and the quality of that entanglement.”

By the third year of operations, CQN expects to have an operational quantum communication testbed that will be able to interoperate two different quantum flows simultaneously for the first time.

  • Quantum repeater
  • Quantum memory (something that can hold onto a qubit for a period of time). In CQN’s case, diamond vacancy color centers which can encode a qubit in a single spin state in an atomic system
  • Quantum-preserving frequency conversion that will allow optical frequency photons carrying the qubits to work on conventional telecom-compatible fiber
  • Very high efficiency single-photon-sensitive detector arrays
  • Transduction interface that can convert qubits from superconducting quantum processors like IBM Q’s to optical frequency photon qubits

Five years into their research, they hope to have built a fully operational quantum repeater that can switch between different types and numbers of nodes on a large network. 

If all goes well, by year ten they expect to demonstrate fault-tolerant entanglement distribution, meaning that quantum data will be exchanged at full quality. Guha compares it to receiving internet service at home:

“Your provider doesn’t tell you they will give you 1 Gigabit/second data but at a fidelity of .9, meaning that you only have a 90% chance of getting your information. We want to have a 100% chance of successful communication over our quantum network.”

Bridging the quantum divide

There’s more to building a bright quantum future beyond getting the technology right. The investigators behind CQN want to learn from the mistakes made in the development of the classical internet, says Jane Bambauer, CQN co-deputy director and UA professor of law.

“There’s still a digital divide,” says Bambauer. “There are still social and pragmatic hurdles to equal access to broadband as well as equal opportunity for jobs in the tech industry, so we’re trying to anticipate a lot of those.”

<strong>Developing quantum skills.</strong> Students work on photonic networks in the Optical Networking Research Lab at the University of Arizona. Courtesy University of Arizona. One way they’re doing that is by taking a proactive approach to education and outreach. CQN will develop a quantum information curriculum, initially targeted at the graduate and undergraduate levels.

They also want to translate those same skills for K-12 education. While it may at first seem far-fetched to teach second graders about quantum entanglement, Bambauer asks, “Why not take some concepts that are palatable, that students can understand and work with and play with, so that as they grow they can think of things in ways that we were never trained to think ourselves?”

Other outreach efforts include a mobile vehicle that will take experiments and demos to remote areas, including Native American communities. 

Both Bambauer and Guha are enthusiastic about the ambitious scope and open-ended aspect of this project. Our quantum future is as yet unwritten, but the center’s cross-disciplinary approach promises plenty of innovations. “We just don’t know what will come out of such wide-spanning transdisciplinary collaborations,” says Guha.

Bambauer adds, “I’m really excited to be part of making sure that we get a pretty good version of all possible quantum internet futures.”

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