Imagine a world without traffic lights; Nothing to guide the flow of traffic, when to stop, or when it’s safe to turn. It would be chaos on the roads. No one likes sitting at a long red light, but it ensures traffic is not only properly queued, but also synchronized in a manner to help people get to where they need to go.  

Waiting in lines isn’t just necessary for humans. For one quantum project, queuing is integral for it to succeed.  

Photon Queue is a quantum company startup mostly led by a group of PhD students from Physics Professor Paul Kwiat’s lab, the Kwiat Quantum Information Group. The company is a participant in Cohort 4 of Duality, a Chicago-based accelerator program solely focused on supporting early-stage companies addressing the important challenges in building quantum tech. Photon Queue is the first startup from the University of Illinois Urbana-Champaign to be accepted into the program, and the first quantum-focused startup to come from the University.  

“Duality offers a lot,” said Nathan Arnold, Physics PhD student and Photon Queue co-founder. “Specifically, they offer a spotlight and a large network of brilliant researchers and investors that are interested in quantum technologies.” 

The company develops efficient quantum memories to expedite the advancement and adoption of quantum communication, computing, and metrology technologies. They do this with technology that stores photonic qubits in free-space reflection cavities. 

“[Our technology] can provide rather efficient storage of single photons, and these single photons are useful and necessary resources for quantum communication protocols and some quantum computation protocols as well,” said Arnold.  

Kwiat offered a visual example of what this would look like: Imagine you’re picking someone up from the airport, but you’re not allowed to stop and wait. Instead, you have to keep circling the airport until the person exits the building. Then you take a different turn, and leave the airport.  

“Our system uses a switch that lets the photons into the ring, and they stay in until we need them, and then we can switch them back out,” explained Kwiat. “The only difference between the airport analogy and photons is photons always go at exactly the same speed, whereas your car can slow down and speed up. That, and the fact that the photons have some small chance each cycle of disappearing entirely, which fortunately doesn’t happen with your car!” 

While useful to the quantum field, the research wasn’t originally meant to be the beginnings of a company. Rather, investigations on the technology began due to a need within the field to store quantum states  

“If you want to go long distances in quantum networking, you need so-called quantum ‘repeaters’, and those all need quantum memories,” said Kwiat. “Our storage method just relies on the fact that it takes a nanosecond for light to go a foot. So if you want to store for 10 nanoseconds, just let the light go around for 10 feet. It seemed like it was a fairly easy thing to do. But it turns out it's not that easy to get the whole thing to work really efficiently.” 

In fact, this research is twenty years in the making, passed down from graduate student to graduate student in Kwiat’s lab. However, it wasn’t until the yet-to-be founders of Photon Queue tackled the research that the idea to base a company around it formed. Although that suggestion didn’t even come from within their own group. 

Photon Queue co-founder Kai Shinbrough, a now-graduated PhD student in Physics Professor Virginia Lorenz’s lab, was studying and working on a different type of quantum memory technology for his PhD. After compiling a comprehensive review of memory technologies for an article in Advances in AMO Physics, he identified a niche for the Photon Queue technology, and approached Kwiat group member, PhD student Colin Lualdi. 

“Kai came up to me and said, ‘You know, Colin, if your memory-enhanced single photon source is so good, then why don’t you think about commercializing it?’” said Colin Lualdi, Physics PhD student and Photon Queue co-founder. “I thought that was an interesting notion.”  

Lualdi and Shinbrough identified the photon-storage element of the source as a starting point for commercialization. After recruiting Arnold, whose work involves similar photon-storage techniques, research continued on the technology. But when it comes to selling a product, there’s a difference between having it work in a lab and then consistently out in the field. In the lab, the set up for this research has to be exceedingly precise.  

For this sort of device to work in the field, it would need to be reliable. Fourth-year Physics PhD student and Photon Queue co-founder Kelsey Ortiz joined the team to assist with that issue.  

“The others reached out to me and asked if I can help design the prototype that we have been working on for IPOC (Illinois Proof-of-Concept Program),” said Ortiz. “We have an initial design started and built which we will be testing more thoroughly.”  

Even though Ortiz is also part of the Kwiat Quantum Information Group, she had been working on a different project involving sending a payload to space. Her experience designing a compact entanglement source, as well as testing it in various thermal and vibrational settings, is particularly useful.  

“There’s a lot of work to be done,” said Ortiz. “We’re going to have to incorporate alignment techniques like an alignment laser that goes through the memory and then have some kind of controller to keep it aligned over time. We’re going to have to test the reliability of that.” 

Almost two years since the idea for Photon Queue was formed, the team of students are now juggling both an up-and-coming quantum company and finishing their PhD studies. Arnold plans on focusing on Photon Queue full time after graduation. Ortiz is also considering joining the company full-time after she completes her PhD in two to three years, but will continue part-time for now. 

“I still have some time to make that decision, but I do see that as an option, just because it’s something exciting and a little scary. I think early on in your career is when you can do those kinds of things,” she said.  

Lualdi likens the experience to being at a buffet: “I feel like I’m at this wonderful buffet with so many fascinating projects that I get to add to my plate,” said Lualdi. “I’m excited to build up Photon Queue as it’s a great opportunity to bridge academic research and industry.”  

Kwiat agreed he too wears several metaphorical hats, but he’s happy to be an advisor on the project. 

“I’m glad that Nathan is interested in taking the company on, of going through all of the other non-science work that’s involved in this in order to make it happen,” said Kwiat. “If no one were willing to do that, then we wouldn’t have any products.” 

Those products have already caught the attention of other companies and groups. It’s a good omen for the future.  

“[These companies] ask, ‘When can we buy this? How much money do I have to give you for you to get me this by next year?’” explained Arnold. “I think one of the reasons that we and a lot of other people are excited about our technology is that it seems to be a very practical approach, something that actually works well enough now to enable different quantum technologies.”