8 June 2022

Researchers Demonstrate Quantum State Measurement in Silicon Carbide

New technique for single-shot readout paves the way to quantum networks

WASHINGTON — Researchers have demonstrated a new technique that enables single-shot readout — a deterministic measurement of the quantum state — in the solid-state material silicon carbide. Until now, single-shot readout hasn’t been demonstrated in silicon carbide because the quantum state is quickly destroyed when readout is attempted.

The new approach paves the way for silicon carbide to bridge the gap between quantum and classical electronic and optical devices by unlocking the ability to perform entanglement distribution and quantum error correction. These capabilities are necessary to create quantum networks and to improve quantum sensing.

Christopher P. Anderson from the University of Chicago will present the new findings at the Optica Quantum 2.0 2022 conference 13 – 16 June 2022. Entitled “Single-Shot Readout of Spin Qubits With Five-Second Coherence Times,” Anderson’s presentation is scheduled for 13:30, 14 June, 2022.

“This was really the last hurdle we had to overcome for this particular quantum platform. Now we are poised to make ultra-secure communication channels, small quantum computers and efficient nanoscale sensors with silicon carbide,” explains Anderson. “For example, the scalability of and robustness of these states leads us to believe we can build un-hackable messaging systems and secure anonymous voting on a national or even global scale.”

Silicon carbide is a mature electronics platform and a leading candidate for creating the telecom quantum repeaters and quantum links necessary to scale a future quantum internet. In addition to its long coherence times and near-telecom single photon emission, the material is commercially available in wafers, compatible with CMOS fabrication techniques and can easily be used to make photonic, electrical and mechanical devices.

To accomplish single-shot readout in silicon carbide, the researchers didn’t use the typical spin-photon method to measure the quantum state. Instead, they mapped the qubit state onto the more robust charge state using spin-to-charge conversion. This all-optical technique allowed them to readout the spin state with over 80% fidelity.

In additional experiments, the researchers demonstrated they could preserve their quantum state for over five seconds, the longest reported quantum coherence time for this type of electron-spin qubit. This was achieved by reducing the magnetic noise in the semiconductor and by applying over 16,000 dynamical decoupling pulses. This long coherence is critical for all quantum technologies. In quantum computers it allows for more operations and computations to be done in the state’s lifetime, while in quantum networks it means that signals can be transported further across a network while still maintaining the quantum correlations. The three orders of magnitude improvement that the researchers demonstrate now means one can envision networks spanning the globe, in contrast to previous millisecond-long coherences which would have limited use to metropolitan scales.

The researchers say that mapping the quantum state onto single charges in silicon carbide not only allows single-shot readout for scalable and coherent quantum nodes but could also allow readout via integration with semiconductor devices.

Anderson added, “We are excited by the possibilities of leveraging silicon carbide as a mature electronics material. We hope to integrate our quantum states into silicon carbide classical devices similar to what one finds in an electric car or LED lightbulb. These devices offer engineered control and readout of charges in the semiconductor, which combined with our ability to translate quantum information into charge information, means we can build a new class of wafer-scale quantum electronic devices.” 

About the Quantum 2.0 2022 conference

The Quantum 2.0 2022 conference aims to stimulate and facilitate the development of quantum information science and technology, particularly for large engineered systems such as quantum computers and simulators, quantum communication networks and arrays of quantum sensors. This year’s meeting will be presented 13 – 16 June 2022 in a hybrid meeting format to accommodate virtual (online) participation as well as in-person attendance at the Encore Boston Harbor in Everett, Massachusetts. Learn more here.

About Optica

Optica (formerly OSA), Advancing Optics and Photonics Worldwide, is the society dedicated to promoting the generation, application, archiving and dissemination of knowledge in the field. Founded in 1916, it is the leading organization for scientists, engineers, business professionals, students and others interested in the science of light. Optica’s renowned publications, meetings, online resources and in-person activities fuel discoveries, shape real-life applications and accelerate scientific, technical and educational achievement. Discover more at: Optica.org

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