New qubit platform: Electrons from a heated light filament (top) land on solid neon (red block), where an electron (represented as a wave function in blue) is captured and manipulated by a superconducting quantum circuit (lower color chip). Credit: Courtesy of Dafei Jin / Argonne National Laboratory
A new qubit platform can transform quantum information science and technology.
No doubt you are looking at this article on a digital device whose basic unit of information is the bit, 0 or 1. Scientists around the world are vying to develop a new type of computer based on the use of quantum bits or qubits.
In an article published May 4, 2022 in the journal Nature, a team led by the US Department of Energy’s Argon National Laboratory (DOE) announced the creation of a new qubit platform formed by freezing neon gas in solids in many low temperature. temperatures, spraying electrons from the filament of a light bulb onto a solid and capturing an electron there. This system has the potential to be developed into perfect building blocks for future quantum computers.
“It seems that the ideal qubit may be on the horizon. Due to the relative simplicity of the electron-on-neon platform, it must be easy to produce at a low cost. “Dafei Jin, an Argon scientist at the Center for Nanoscale Materials.”
In order to realize a useful quantum computer, the quality requirements of qubits are extremely demanding. Although there are different forms of qubits today, none of them is optimal.
What would make an ideal qubit? According to Dafei Jin, an Argon scientist and chief researcher of the project, he has at least three excellent qualities.
It can stay in both 0 and 1 conditions (remember the cat!) For a long time. Scientists call this long “coherence.” Ideally, this time would be about a second, a time step that we can take on a home clock in our daily lives.
Second, the qubit can be changed from one state to another in a short time. Ideally, this time would be about one billionth of a second (nanosecond), a step in the time of a classic computer clock.
Third, the qubit can be easily connected to many other qubits so that they can work in parallel with each other. Scientists call this connection entanglement.
Although currently well-known qubits are not perfect, companies such as IBM, Intel, Google, Honeywell and many startups have chosen their favorite. They are aggressively striving for technological improvement and commercialization.
“Our ambitious goal is not to compete with these companies, but to discover and build a fundamentally new qubit system that can lead to an ideal platform,” said Gene.
Although there are many options for choosing qubit types, the team chose the simplest – a single electron. Heating a simple light thread that you can find in a toy can easily launch an endless supply of electrons.
One of the challenges for every qubit, including the electron, is that it is very sensitive to disturbances from its surroundings. So the team chose to capture an electron on a super-pure solid neon surface in a vacuum.
Neon is one of a handful of inert elements that do not react with other elements. “Because of this inertia, solid neon can serve as the cleanest possible solid in a vacuum to receive and protect all qubits from disturbance,” said Gene.
A key component in the team’s qubit platform is a microwave resonator with a chip made of superconductor. (The much larger home microwave is also a microwave resonator.) Superconductors — metals without electrical resistance — allow electrons and photons to interact at near-absolute zero with minimal loss of energy or information.
“The critical microwave resonator provides a way to read the state of the qubit,” said Cather Merch, a professor of physics at the University of Washington in St. Louis and a senior co-author. “It concentrates the interaction between the qubit and the microwave signal. This allows us to take measurements showing how well the qubit is working. “
“With this platform, we have for the first time achieved a strong bond between an electron in a near-vacuum environment and a microwave photon in a resonator,” said Xianjing Zhou, a PhD student at Argonne and the first author of the paper. “This opens up the possibility of using microwave photons to control each electronic qubit and connect many of them in a quantum processor,” Zhou added.
“Our qubits are actually as good as the ones humans have been developing for 20 years.” – David Schuster, professor of physics at the University of Chicago and senior co-author
The team is testing the platform in a scientific instrument called a dilution refrigerator, which can reach temperatures as low as 10 milligrades above absolute zero. This tool is one of many quantum capabilities at the Argon Nanoscale Materials Center, a facility for DOE Office of Science users.
The team performs real-time operations with an electronic qubit and characterizes its quantum properties. These tests have shown that solid neon provides a stable environment for an electron with very low electrical noise to disturb it. Most importantly, the qubit achieved times of coherence in the quantum state, competing with the most modern qubits.
“Our qubits are actually as good as the ones humans have been developing for 20 years,” said David Schuster, a professor of physics at the University of Chicago and a senior co-author. “This is just our first series of experiments. Our qubit platform is not nearly optimized. We will continue to improve coherence times. And because the speed of this qubit platform is extremely fast, just a few nanoseconds, the promise to increase to a very tangled qubit is important. ”
There is another advantage of this remarkable qubit platform. “Due to the relative simplicity of the electron-on-neon platform, it should be easy to produce at a low cost,” said Gene. “It seems that the ideal qubit may be on the horizon.
Reference: “Single electrons on solid neon as a solid state qubit platform” by Xianjing Zhou, Gerwin Koolstra, Xufeng Zhang, Ge Yang, Xu Han, Brennan Dizdar, Xinhao Li, Ralu Divan, Wei Guo, Kater W. Murch, David I. Schuster and Dafei Jin, May 4, 2022, Nature.DOI: 10.1038 / s41586-022-04539-x
The team published its findings in a Nature article entitled “Single Electrons on Solid Neon as a Solid State Qubit Platform.” In addition to Jin and Zhou, Argonne’s associates include Xufeng Zhang, Xu Han, Xinhao Li and Ralu Divan. In addition to David Schuster, the University of Chicago staff includes Brennan Dizdar. In addition to Cutter Merch of the University of Washington in St. Louis, other researchers include Wei Guo of Florida State University, Gervin Colstra of Lawrence Berkeley National Laboratory, and Ge Young of the Massachusetts Institute of Technology.
Funding for Argonne’s research comes primarily from DOE’s Office of Basic Energy Sciences, Argonne’s R&D program, and the Julian Schwinger Foundation for Physical Research.
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