Exploring Isolated Double-Quantum-Dot Detectors for Scalable Quantum Computing Architectures

With the progress made in advanced semiconductor manufacturing and in control and readout techniques, semiconductor based quantum computing has made significant progress in the past decade in both fidelities and coherence times. In view of scalability, an elementary computational unit that can retain key computational functionalities must be defined so that an array of such units can process information without excessive overhead. For quantum computation to proceed, not only should each qubit be able to perform operations in all dimensions about the Bloch sphere, but the detection of quantum states, either spin or charge, should also be fast, robust, and efficient. As the number of ancilla qubits needed for error correction scales with the number of computational qubits, there is a need for highly scalable, reproducible designs with a density sufficient to allow error correction. Finally, a cost-effective solution that maintains high compatibility with industry standards is needed to ensure industrialisation of such a unit. A compact arrangement eases scalability and allows a higher qubit density, while the versatility of such an architecture allows the circumvention of potentially defective or otherwise unusable portions of large-scale structures. This would allow minimising the footprint typically dedicated to error correction. This thesis proposes such an elementary unit in the form of a quadruple quantum-dot fabricated by a standard silicon-based Complementary metal- oxide-semiconductor (CMOS) process. Firstly, we show the flexibility of this device by reconfiguring the structure as a single-electron box (SEB) detector and as various double-quantum-dot (DQD) detector configurations. In all cases, we demonstrate a high fidelity fast readout exceeding 99.8% in 10µs. Finally, we discuss the ability for the DQD detector to exceed the performance of the SEB detector in an isolated quantum-dot array by thermalising with the lower temperature of T ≈42 ±2 mK as opposed to the electron temperature Te ≈139 ±4 mK.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Ulas, Kalid

Advisor dc:contributor.advisor

• Smith, Charles

• charge sensing
• CMOS
• double-quantum-dots
• electron temperature
• fidelity
• measurement fidelity
• physics
• quantum computers
• quantum computing
• quantum-dots
• qubit fidelity
• radio-frequency reflectometry
• reflectometry
• semiconductors
• silicon
• silicon quantum-dot
• single-electron transistor
• spin qubits

Licence

• https://www.repository.cam.ac.uk/bitstreams/b3bf2fa5-2263-4271-8c9c-0d4ed298c971/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.125326

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/396008