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500 ps Charge Coherence Achieved in Bilayer Graphene Quantum Dots

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June 14, 2026 by Ivy Delaney

Researchers have measured charge decoherence times between 400 and 500 picoseconds in bilayer graphene double quantum dots, a result achieved using both Landau-Zener-Stückelberg-Majorana (LZSM) interference and photon assisted tunneling. This consistency across different measurement methods suggests bilayer graphene is a promising material for developing highly tunable quantum dots with potential application as spin and valley qubits, essential components in quantum computing. The coherent dynamics were measured using an arbitrary waveform generator and analog microwave source from Keysight, demonstrating a practical approach to studying these quantum systems. Interference spectroscopy, used to study charge noise and decoherence, reveals the potential of these graphene-based quantum dots for advanced quantum technologies.

Bilayer Graphene Quantum Dots Enable Coherent Charge Oscillations

Bilayer graphene is rapidly becoming a key material in the pursuit of functional quantum dots, specifically for realizing spin and valley qubits, due to its tunable properties and potential for scalability. Recent experiments demonstrate coherent charge oscillations within bilayer graphene double quantum dots, a phenomenon leveraged to probe the underlying quantum behavior of these nanoscale structures. Keysight’s arbitrary waveform generator and analog microwave source played a crucial role in characterizing these oscillations, enabling precise control and measurement of the quantum system’s dynamics. All experimental control and data acquisition were managed through Labber, a lab control and automation software package. This ability to reliably induce and measure coherent charge oscillations opens avenues for deeper investigation into charge noise and decoherence mechanisms within semiconductor quantum dots. The consistent decoherence times achieved represent a significant step towards harnessing graphene quantum dots for practical quantum information processing, as longer coherence is vital for maintaining quantum information. Interference spectroscopy, a technique employed in these studies, allows for detailed analysis of the factors limiting coherence and provides insights for material and device optimization.

In this case study, we provide an introduction into the measurement of coherent charge oscillations using a Keysight arbitrary waveform generator (AWG) and an analog microwave source.

Keysight

This material is gaining traction as a platform for quantum dots, specifically for potential spin and valley qubits, which could underpin future quantum computing architectures. These findings suggest bilayer graphene’s increasing viability for advanced quantum technologies.

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Ivy Delaney

Ivy Delaney has been working with neural networks and machine learning since the mid-nineties, back when a couple of hidden layers and a long afternoon of training counted as ambitious. She has watched the field go from academic curiosity to the thing quietly running underneath everything, and she brings that long view to quantum computing. For Quantum Zeitgeist she covers the ground where the two fields meet. That means quantum machine learning and the variational algorithms it leans on, and it also means the less glamorous but more interesting story of classical machine learning already doing real work inside quantum machines, decoding error-correcting codes, calibrating noisy hardware and learning the error models that simulators depend on. She writes about the hardware those algorithms have to run on too, and about the post-quantum cryptography scramble that the same hardware has set off. Her stories typically start with the paper, whether that is peer-reviewed work, conference proceedings or an arXiv preprint, with the source linked so you can hold a claim up against the research it came from. She is unimpressed by benchmarks that will not say what they beat, and by demonstrations that only work in the press release.

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