Jellybeans: A sweet solution for overcrowded circuitry in quantum computer chips
—Undefined Trio
Engineers at UNSW Sydney have made significant progress in addressing the challenge of overcrowding in quantum computer chips. In a study published in Advanced Materials, they introduced the concept of jellybean quantum dots, elongated areas between qubit pairs that create more space for wiring without disrupting the interaction between the paired qubits. This breakthrough offers a potential solution to the space constraints faced by quantum computers, which require millions of wires to connect the multitude of qubits.
While jellybean quantum dots have been explored in various material systems, this study demonstrated their feasibility in silicon for the first time. Silicon is a crucial material in quantum computing due to its existing infrastructure for producing quantum computing chips and the high qubit density it can accommodate. However, the close proximity required for qubits to share information posed a challenge for wiring connections.
The researchers showed in the lab that jellybean quantum dots can be implemented in silicon. This breakthrough allows qubits to be spaced apart, enabling the integration of necessary wires between them for connectivity and control.
In a normal quantum dot using spin qubits, single electrons are used to represent computational states. To implement a quantum algorithm, two-qubit gates are required, where the control of one qubit depends on the state of the other. Previously, this necessitated placing the quantum dots very close together, limiting space for wiring. The jellybean solution overcomes this challenge by creating a chain of electrons, with additional electrons trapped between the qubits. This enables the qubits at each end of the jellybean to communicate while maintaining their influence on each other. The electrons in the jellybean dot play a crucial role in facilitating interaction while spread apart.
The study found that the number of extra electrons pulled into the jellybean quantum dot determines its arrangement. With a smaller number of electrons, the jellybean breaks into smaller sections, whereas a larger number of electrons creates a more continuous and homogeneous jellybean with well-defined spin and quantum states for qubit coupling.
While this study focused on demonstrating the feasibility of jellybean quantum dots, further research is needed to integrate functional qubits and enable communication between them.
"We are excited to try implementing them with qubits next," says Associate Professor Arne Laucht from UNSW Sydney, emphasizing that there is still much work to be done.
The utilization of jellybean quantum dots in silicon quantum computers could provide a valuable solution for overcoming the space limitations and enable the scaling up of quantum computing capabilities.
Reference: Zeheng Wang et al, Jellybean Quantum Dots in Silicon for Qubit Coupling and On‐Chip Quantum Chemistry, Advanced Materials (2023). DOI: 10.1002/adma.202208557
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