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New Results from RIKEN Show A New Model for Scalability in Silicon Quantum Dots

the RIKEN institute in Japan has created a new theoretical model which can expand the dephasing time in silicon quantum dots
By Kenna Hughes-Castleberry posted 29 May 2023

Silicon is the backbone of the modern electronics industry, and its fabrication processes are well-established and widely used. Silicon quantum dots can be fabricated using similar techniques, allowing seamless integration with existing silicon-based electronics. New research from the Japanese institute RIKEN has pushed the capabilities of silicon quantum dots even further, as scientists have created a new theoretical framework that could expand the lifespan of these quantum dots, allowing for further scalability on a quantum computer. The results they published in Physical Review Letters.

Looking at Dephasing

“The model predicts sweet spots for the hole-spin dephasing, which are sensitive to device details such as dot size and asymmetry, growth direction, and applied magnetic and electric fields,” explained Dr. Benjamin Delsol, an IP strategist and quantum computing expert. “These sweet spots refer to the specific conditions where the dephasing time is optimized, leading to improved performance of the hole-spin qubit.” Dephasing occurs when the coherence or synchronization within a system decays over time, forcing the system back into its initial state. Extending the dephasing time is essential as it allows the quantum computer more time for computation and readout.

By adding other variables to their theoretical model, the RIKEN researchers saw something interesting happen to the dephasing. As Delsol elaborated, “The researchers found that the new terms introduced in their model give rise to these sweet spots, and they estimate that the dephasing time at these sweet spots is boosted by several orders of magnitude, up to the order of milliseconds. This significant improvement in the dephasing time indicates that the model elongates the coherence time of the hole-spin qubit, which is crucial for developing more efficient and reliable quantum devices.”

Bigger Picture Effects

Thanks to this theoretical model from RIKEN, an increase in dephasing for these silicon quantum dots could have some significant impacts. “By understanding the specific conditions that lead to optimized dephasing times, designers can fine-tune the device parameters, such as dot size, asymmetry, growth direction, and applied magnetic and electric fields, to achieve the best possible performance for hole-spin qubits,” added Delsol. Besides device optimization, a longer dephasing time allows for improved performance for the quantum computer. “The model’s prediction of sweet spots, where several orders of magnitude boost the dephasing time, can help improve the overall performance of quantum computing devices,” said Delsol. “This is because longer coherence times allow for more complex quantum operations to be performed before the qubit loses its coherence, which is essential for quantum computing.” Other benefits associated with longer dephasing time include better reliability of the system and a guide for experimental efforts.

For those developing quantum computers on silicon quantum dots, this new theoretical framework can act as a template for leveraging the ability of these minuscule but powerful devices.

RIKEN Results in Real Life

The benefits of enhanced dephasing within the silicon quantum dot system are not limited to local effects. Instead, as Delsol explained, they can influence many aspects of the quantum computing industry. “Silicon is a widely used material in the semiconductor industry, and its compatibility with industrial fabrication makes it an attractive option for building scalable quantum computers,” added Delsol. “This could lead to more efficient and cost-effective manufacturing of quantum computing devices. Using holes in silicon-based quantum-dot systems offers several advantages, such as reduced susceptibility to nuclear noise, stronger spin-orbit coupling, and full-electric control. These advancements could significantly impact the development of quantum computing technologies and expand their use cases across various industries.” As issues of noise and coupling have been obstacles for many quantum computing companies, possible solutions like this theoretical model could be effective in accelerating the development of these next-generation computers.

For the RIKEN team, the next steps are to validate their new model in the laboratory. “This would involve designing and fabricating silicon quantum dot devices under the conditions identified as sweet spots and measuring the dephasing time to verify the model’s accuracy,” Delsol stated. After validation, engineers can then utilize the theory for silicon quantum dot improvement. “With a better understanding of the factors that influence hole-spin dephasing, researchers can focus on optimizing the device parameters, such as dot size, asymmetry, growth direction, and applied magnetic and electric fields, to achieve the best possible performance for hole-spin qubits,” added Delsol.

As silicon quantum dots have emerged as a promising platform for quantum computing, new developments in their capabilities can offer unique advantages that make them significant in the field of quantum computing.

Kenna Hughes-Castleberry is a staff writer at Inside Quantum Technology and the Science Communicator at JILA (a partnership between the University of Colorado Boulder and NIST). Her writing beats include deep tech, quantum computing, and AI. Her work has been featured in Scientific American, Discover Magazine, Ars Technica, and more.

Categories: quantum computing

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