From University of Chicago: “For first time researchers send entangled qubit states through a communication channel”

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From University of Chicago

Feb 26, 2021
Emily Ayshford

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Quantum engineer Youpeng Zhong works on a quantum assembly in the lab of Andrew Cleland at the University of Chicago’s Pritzker School of Molecular Engineering(US). Credit: Nancy Wong.

In a breakthrough for quantum computing, University of Chicago researchers have sent entangled qubit states through a communication cable linking one quantum network node to a second node.

The researchers, based in the Pritzker School of Molecular Engineering(US) at the University of Chicago(US), also amplified an entangled state via the same cable first by using the cable to entangle two qubits in each of two nodes, then entangling these qubits further with other qubits in the nodes.

The results, published Feb. 24 in Nature, could help make quantum computing more feasible and could lay the groundwork for future quantum communication networks.

“Developing methods that allow us to transfer entangled states will be essential to scaling quantum computing,” said Andrew Cleland, the John A. MacLean Sr. Professor of Molecular Engineering Innovation and Enterprise, who led the research.

Sending entangled photons through a network

Qubits, or quantum bits, are the basic units of quantum information. By exploiting their quantum properties, like superposition, and their ability to be entangled together, scientists and engineers are creating next-generation quantum computers that will be able solve previously unsolvable problems.

Cleland’s group uses superconducting qubits, tiny cryogenic circuits that can be manipulated electrically.

To send the entangled states through the communication cable—a one-meter-long superconducting cable – the researchers created an experimental set-up with three superconducting qubits in each of two nodes. They connected one qubit in each node to the cable and then sent quantum states, in the form of microwave photons, through the cable with minimal loss of information. The fragile nature of quantum states makes this process quite challenging.

Cleland’s former postdoctoral fellow, paper first author Youpeng Zhong, was able to develop a system in which the whole transfer process—node to cable to node—takes only a few tens of nanoseconds (a nanosecond is one billionth of a second). That allowed them to send entangled quantum states with very little information loss.

The system also allowed them to “amplify” the entanglement of qubits. The researchers used one qubit in each node and entangled them together by essentially sending a half-photon through the cable. They then extended this entanglement to the other qubits in each node. When they were finished, all six qubits in two nodes were entangled in a single globally entangled state.

Creating a scaled networked quantum computer

In the future, quantum computers will likely be built out of modules where families of entangled qubits conduct a computation. These computers could ultimately be built from many such networked modules, similar to how supercomputers today conduct parallel computing on many central processing units connected to one another. The ability to remotely entangle qubits in different modules, or nodes, is a significant advance to enabling such modular approaches.

“These modules will need to send complex quantum states to each other, and this is a big step toward that,” Cleland said. A quantum communication network could also potentially take advantage of this advance.

Cleland and his group hope to next extend their system to three nodes to build three-way entanglement.

“We want to show that superconducting qubits have a viable role going forward,” he said.

Other authors on the paper include David Schuster, associate professor of physics and molecular engineering; graduate students Hung-Shen Chang, Ming-Han Chou, Christopher R. Conner, Joel Grebel, Rhys G. Povey, and Haoxiong Yan; and former postdoctoral researchers Étienne Dumur and Audrey Bienfait.

See the full article here .

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One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

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In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts. The University of Chicago is a private research university in Chicago, Illinois. Founded in 1890, its main campus is located in Chicago’s Hyde Park neighborhood. It enrolled 16,445 students in Fall 2019, including 6,286 undergraduates and 10,159 graduate students. The University of Chicago is ranked among the top universities in the world by major education publications, and it is among the most selective in the United States.

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One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

UChicago research has led to such breakthroughs as discovering the link between cancer and genetics; establishing revolutionary theories of economics; and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations.

The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.