A team of scientists at the Pritzker School of Molecular Engineering at the University of Chicago announced the discovery of a simple modification that allows quantum systems to remain operational 10,000 times longer – as “coherent” – than before. Credit: University of Chicago
Simple Innovation expects that several new avenues will open up for quantum science.
If we can take advantage of it, quantum technology promises fantastic new possibilities. But first, scientists need to coax quantum systems to stay jock longer than a few millionths of a second.
A team of scientists at the University of ChicagoThe Pritzker School of Molecular Engineering announced the discovery of a simple modification that allows quantum systems to remain operational – or “coherent” – 10,000 times longer than before. Although the scientists tested their technique on a particular class of quantum systems called qubits with solid state, they think it should apply to many other types of quantum systems and could therefore revolutionize quantum communication, computing and sensing.
The study was published on August 13, 2020, in Science.
Postdoctoral researcher Kevin Miao is working on quantum research at the Pritzker School of Molecular Engineering at the University of Chicago. Credit: David Awschalom / University of Chicago
“This breakthrough lays the groundwork for exciting new avenues for quantum science research,” said student author David Awschalom, the Liew Family Professor in Molecular Engineering, senior scientist at Argonne National Laboratory and director of the Chicago Quantum Exchange. “The broad application of this discovery, coupled with a remarkably simple implementation, allows this robust coherence to influence many aspects of quantum engineering. It makes new research opportunities possibly thought rather unattractive. ”
Down to the atomic level, the world works according to the rules of quantum mechanics – very different from what we see around us in our daily lives. These different rules could translate into technology such as virtually unhackable networks or extremely powerful computers; the US Department of Energy published a blueprint for the future quantum internet at an event in UChicago on July 23. But fundamental technical challenges remain: Quantum states need an extremely quiet, stable space to operate, as they are easily disturbed by background noise vibrations, temperature changes or scattered electromagnetic fields.
So scientists are trying to find ways to keep the system coherent for as long as possible. One common approach is to physically isolate the system from the noisy environment, but this can be tricky and complex. Another technique involves making all materials as clean as possible, which can be costly. The scientists at UChicago took a different approach.
“With this approach, we do not try to eliminate noise in the surroundings; instead, we “trick” the system into thinking it has no sound, “said postdoctoral researcher Kevin Miao, the paper’s first author.
From left: Scientists Kevin Miao, Chris Anderson and Alexandre Bourassa are working on quantum research in the Awschalom lab at the Pritzker School of Molecular Engineering at the University of Chicago. Credit: David Awschalom / University of Chicago
In tandem with the usual electromagnetic pulses that were used to control quantum systems, the team applied an additional continuously alternating magnetic field. By precisely setting this field, the scientists were able to rotate the electron spins rapidly and allow the system to “tune” the rest of the sound.
“To get a sense of the principle, it’s like sitting on a merry-go-round with people screaming around you,” Miao explained. “When the ride is still quiet, you can hear them perfectly, but when you turn fast, the sound disappears into a background.”
This small change left the system cohesive for up to 22 milliseconds, four orders of magnitude higher than without the modification – and much longer than any previously reported electron spin system. (For comparison, a blink of an eye takes about 350 milliseconds). The system is able to attenuate some forms of temperature fluctuations, physical vibrations, and electromagnetic noise almost completely, all of which usually destroy quantity coherence.
The simple fix could unlock discoveries in virtually any area of quantum technology, the scientists said.
“This approach creates a path to scalability,” Awschalom said. “It should make the storage of quantum information in electron spin practical. Extended storage times can enable more complex operations in quantum computers and allow quantum information sent from spin-based devices to travel longer distances in networks. “
“With this approach, we do not try to eliminate noise in the surroundings; instead, we “trick” the system into thinking it is not experiencing sound. ”- Kevin Miao, postdoctoral researcher
Although their tests were performed in a solid state quantum system using silicon carbide, the scientists believe that the technique should have similar effects in other types of quantum systems, such as superconducting quantum bits and molecular quantum systems. This level of versatility is unusual for such a technical breakthrough.
“There are a lot of quantum technology candidates who were pushed aside because they could not maintain quantitative coherence for long periods of time,” Miao said. “That could be re-evaluated now that we have this way of improving cohesion.
“The best part is, it’s incredibly easy to do,” he added. “The science behind it is complicated, but the logistics of adding an alternating magnetic field are very simple.”
Other UChicago scientists on the study were graduate student Joseph Blanton, postdoctoral researcher Chris Anderson, graduate students Alexandre Bourassa and Alex Crook, and Argonne scientist Gary Wolfowicz. Hiroshi Abe and Takeshi Ohshima with Japanese National Institutes of Quantum and Radiological Science and Technology were also co-authors. The team used resources at the Pritzker Nanofabrication Facility. The team is working with the Polsky Center for Entrepreneurship and Innovation to commercialize the discovery.
Reference: “Universal Coherence Protection in a Solid State Qubit” by Kevin C. Miao, Joseph P. Blanton, Christopher P. Anderson, Alexandre Bourassa, Alexander L. Crook, Gary Wolfowicz, Hiroshi Abe, Takeshi Ohshima, and David D. Awschalom, August 13, 2020, Science.
DOI: 10.1126 / science.abc5186
Financing: DARPA, Air Force Office of Scientific Research, Office of Naval Research, National Science Foundation, Japan Society for the Promotion of Science.
