US Army Helps Develop Hybrid Quantum Computing with New Research

Researchers combined quantum systems for the first fime and received promising results.
Fabienne Lang

The world is another step closer to living with quantum computers, as U.S. Army researchers worked alongside University of Maryland scientists to build the precursor to a hybrid quantum computing system

The system has shown promising results, something that will be useful for the future. 

What did the team discover?

For the first time, the Army and the University of Maryland researchers demonstrated that two-photon interference between photons from a trapped ion system and a neutral atom system is possible. Moreover, it may assist in speeding up the process towards quantum computers of the future. 

A two-photon interference, also known as the Hong-Ou-Mandel effect, happens when two identical photons enter a beam splitter from different input ports, however, they exit via the same port. 

By working with trapped ion systems as well as neutral atom systems, future quantum networks will benefit from both leading approaches and their strengths, while overcoming individual weaknesses, as per the researchers. 

"Trapped ions have the highest fidelity quantum operations reported and neutral atoms are excellent at manipulating photons that carry quantum information," explained Dr. Qudsia Sara Quraishi, a physicist at the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory.


The researchers installed a trapped ion system in one building at the University of Maryland, and a neutral atom system in another building, linking them with fiber lines.

"One lab has a beam splitter that allows the photon two paths to exit; there’s a 50 percent chance of it coming out of one port and a 50 percent chance of it coming out the second port," said John Hannegan, a fourth-year graduate student in Quraishi’s lab.

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"If you send two individual photons into the beam splitter, you’d expect that each photon to select an output port independently; however, due to quantum interference, photons with identical properties that arrive at the beam splitter bunch together, meaning they always leave the same port together, not individually."

What stood out about this experiment is that the team managed to turn the two different quantum systems into one identical one, strong enough to create quantum interference. 

Quraishi explained that the team's results push forward quantum information research hugely. 

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