Scientists at QuTech have developed a method to operate large arrays of quantum dots using far fewer control lines.
By assigning dot coordinates like squares on a chessboard, they enabled the biggest gate-defined quantum dot system yet.
Quantum dots are leading qubit candidates that currently require dedicated control lines for each dot. This lacks scalability compared to classical transistors with shared addressing.
The researchers’ chessboard technique assigns quantum dots X-Y coordinates. Combined horizontal and vertical lines allow individual manipulation of any dot, just like chess pieces.
This scheme lets them control a 4×4 grid of 16 quantum dots using minimal wiring. Lead author Francesco Borsoi notes this reduction enables scaling to millions of addressable qubits with only thousands of lines.
The breakthrough provides a roadmap to practical systems requiring massively interconnected qubits. Previous 1-to-1 dot-line schemes face daunting wiring complexities for large grids.
The team also recently set fidelity records exceeding 99.99% for this quantum dot type using germanium. This material’s properties aid quantum performance.
Principal investigator Menno Veldhorst sees near-term potential in applying their grids as quantum simulators. Recently, they successfully simulated a basic physics model of bond resonances.
Extending simulations to larger quantum dot arrays could provide new insights into longstanding physics questions. Veldhorst concludes that combining scalability, high performance, and simulation versatility makes their quantum grids highly promising.
Pushing the frontiers of controllable quantum systems will require interconnecting many such grid circuits through quantum links. By borrowing from chessboards, the researchers’ creative addressing scheme brings this interconnectivity goal closer.
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Francesco Borsoi et al, Shared control of a 16 semiconductor quantum dot crossbar array, Nature Nanotechnology (2023). DOI: 10.1038/s41565-023-01491-3