Scientists demonstrate a new method for stretching the length of time qubits can maintain information -- by disrupting the symmetry of their environment.
Scientists have demonstrated that they can extend the lifetime of a molecular qubit by altering the surrounding crystal's structure to be less symmetrical.
The asymmetry protects the qubit from noise, enabling it to maintain information for five times longer than if it were housed in a symmetrical structure. The research team achieved a coherence time -- the time the qubit maintains information -- of 10 microseconds, or 10 millionths of a second, compared to the 2 microsecond coherence time of a molecular qubit in a symmetrical crystal host.
"This newfound ability to chemically control the host environment opens up new space for targeted applications of molecular qubits." -- Danna Freedman, MIT
The result, published in Physical Review X, comes from a team of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory, MIT, Northwestern University, The University of Chicago and the University of Glasgow. The result is supported in part by Q-NEXT, a DOE National Quantum Information Science Research Center led by Argonne.
A bit of background
Why it matters
"Molecular chemistry enables us to swap out the crystalline material that hosts the qubit as well as modify the qubit itself," said Danna Freedman, F.G. Keyes Professor of Chemistry at MIT and paper co-author. "Adding in this new level of control is very powerful."
"The change was realized just by interchanging single atoms on the host molecules, one of the smallest changes you could get, and it gave rise to the five-fold enhancement in coherence time," said University of Glasgow's Sam Bayliss, who co-authored the study. "It's a nice demonstration of this atomic-level tunability that you get with molecules. Chemical techniques intrinsically provide control on the level of single atoms, which is a dream in a lot of modern technologies."
"We've created a new handle for modifying coherence properties in molecular systems," Freedman said. "This newfound ability to chemically control the host environment opens up new space for targeted applications of molecular qubits."
"While 10 microseconds may not sound extremely long compared to some systems, keep in mind that we didn't do anything to reduce the noise sources. In the environments we measured, the noise is very significant. So even though there's noise there, the qubits basically don't see it," Bayliss said. "And why don't we just remove the noise source? In practical cases, it's not always possible to operate in an environment that is ultrapure. So having a qubit that can operate intrinsically in a noisy environment can be advantageous."
"This is incredibly exciting for us," Bayliss said. "One of the very exciting things was just how much of an advancement could be made with these systems over a short space of time, and how small some of the modifications to the host matrix can be to get quite a significant improvement."
"I'm delighted to observe a new, exciting feature of molecular chemistry," Freedman said.
"This is an important development. Being able to precisely tune a qubit's environment is a unique advantage of molecular qubits. This can't be easily done within other material systems," said Q-NEXT Director and paper co-author David Awschalom, who is also an Argonne senior scientist, vice dean of Research and Infrastructure and the Liew Family Professor of Molecular Engineering and physics at the University of Chicago's Pritzker School of Molecular Engineering, and the director of the Chicago Quantum Exchange. "Knowing we can extend a qubit's lifetime by engineering its environment opens new possibilities for applications across quantum computing, sensing, and communication."
This work was supported by the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers and the Office of Basic Energy Sciences.
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