To build the quantum internet, UChicago engineer is teaching atoms how to remember

When the quantum internet arrives, researchers predict it will change the computing landscape on a scale unseen in decades. In their opinion, hacking will become a thing of the past. It will secure global power grids and voting systems. It will enable almost unlimited computing power and allow users to securely transmit information over great distances.

But for Tian Zhong, an assistant professor at the Pritzker School of Molecular Engineering (PME) at the University of Chicago, the most tantalizing benefits of the quantum internet have yet to be envisioned.

Zhong is a quantum engineer working to create this new global network. According to him, the full impact of the quantum internet can only be realized after it is built. To understand his work and why the United States is spending $625 million on the new technology, it helps to consider the science behind it: quantum mechanics.

Quantum mechanics is a theory developed to explain fundamental properties of matter, especially at the subatomic scale. Its roots go back to the late 1800s and early 1900s, when scientists attempted to explain the unusual nature of light, which behaves as both a wave and a particle. In the hundred years since, physicists have learned a lot, especially about the strange behavior of subatomic particles.

For example, they learned that some subatomic particles have the ability to be in two states at the same time, a principle called superposition. Another such principle is entanglement, the ability of two particles to instantly “communicate” despite being hundreds of miles apart.

Over time, scientists have found ways to manipulate those principles, entangle particles at will, or control an electron’s spin. That new control allows researchers to encode, transmit and process information using subatomic particles, laying the foundation for quantum computers and the quantum internet.

At the moment, both technologies are still hampered by certain physical limitations — quantum computers, for example, must be kept in giant freezers below freezing — but researchers like Zhong are optimistic those limitations will be resolved in the near future.

“We are at a crossroads where this is no longer science fiction,” Zhong said. “It looks more and more like this technology will come out of labs every day, ready to be adopted by society.”

The right tool for the job

Zhong’s research focuses on the hardware needed to realize the quantum internet, things like quantum chips that encrypt and decrypt quantum information, and quantum repeaters that relay information over network lines. To make that hardware, Zhong and his team work on a subatomic scale, using individual atoms to hold information and single photons to transmit it over optical cables.

Zhong’s current work focuses on finding ways to combat quantum decoherence, which is when information stored on a quantum system deteriorates to the point that it can no longer be retrieved. Decoherence is a particularly difficult obstacle to overcome, because quantum states are extremely sensitive and any outside force – be it heat, light, radiation or vibration – can easily destroy it.

Most researchers tackle decoherence by keeping quantum computers at temperatures around absolute zero. But once a quantum state is sent outside the freezer, say on a network line, it starts to break down within microseconds, severely limiting the potential for extensive interconnectivity.

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