Proposed probe chip a potential shortcut for quantum device manufacturing cycle

Quantum dot spin qubits are a promising technology for quantum computing. However, because of the difficulty to fabricate and characterize new quantum dot spin qubit devices, their development progress has been slow compared to competing technologies such as superconducting qubits and trapped ion qubits

Shim et al. propose a new method to make the characterization process of these devices easier — by incorporating separate probe chips that would allow quick measurements of the semiconductors hosting these qubit devices.

The proposed separate probe chip possesses circuitry capable of both inducing quantum dots on the target semiconductor and measuring properties of the semiconductor. Inducing quantum dots instead of fabricating them would allow nondestructive characterization of the qubit, making the characterization process easier.

The authors considered how their proposed probe could directly and non-invasively measure valley splitting, a material property that affects the performance of electron spin qubits in silicon quantum devices. The separate probe chip would use the quantum capacitance of the quantum dots, which depend on the electron configuration within the dots, to take microwave reflectometry measurements related to valley splitting.

Their numerical simulations indicate that the separate probe chip method is feasible for silicon-based quantum dots using current state-of-the-art experimental techniques. But according to Yun-Pil Shim, an author of the paper, their proposed method should also be applicable to materials and systems beyond silicon. The team plans to explore other systems and work with collaborators to carry out a proof-of-concept experiment in the future.

Source: “Induced quantum dot probe for material characterization,” by Yun-Pil Shim, Rusko Ruskov, Hilary M. Hurst, and Charles Tahan, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5053756 .