Isolated Bottom Corner Gates for Fin Spin-Qubit Coherence
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Solution Overview
Problem
Qubits implemented on silicon-on-insulator (SOI) technology face issues with increased charge noise at the buried oxide interface, challenging qubit tuning due to simultaneous effects on occupation, tunnel coupling, and g-factor, and existing ESR drive lines have a large footprint difficult to integrate close to qubits.
Innovation Solution
The implementation of isolated bottom corner gates along a fin in qubit devices, which are electrically isolated and used to apply electric potential, electric field, magnetic field, and AC electromagnetic fields for spin-qubits, enabling local control and higher device density through self-aligned fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ESR drive lines are integrated close to qubits, then qubit coherence is improved, but the footprint area increases making integration difficult
Solution Approach 1:
The ESR drive line functionality is segmented into two separate bottom corner gates positioned at opposite corners of the fin. This segmentation allows the drive line to be integrated close to the qubit without requiring a large continuous footprint, as the separated gates can be independently controlled to generate the necessary oscillating magnetic field for ESR.
Solution Approach 2:
The ESR drive line is transitioned from a planar configuration to a three-dimensional configuration by utilizing the vertical dimension and corner positions of the fin structure. The bottom corner gates are positioned at the corners of the fin cross-section, utilizing the spatial dimensionality of the fin to achieve close integration without increasing the planar footprint.
2Adaptability or versatility
If bottom corner gates are used for local control, then tunability is improved, but device complexity increases
Solution Approach 1:
Multiple functions are merged into the bottom corner gates structure. The same bottom corner gates that provide local electrostatic control for quantum dot formation and tuning also serve as the ESR drive lines when driven with oscillating signals. This merging eliminates the need for separate control structures, reducing overall device complexity while maintaining high tunability.
Solution Approach 2:
The bottom corner gates are designed with multi-functionality, serving both as electrostatic control elements for quantum dot tuning and as ESR drive lines for spin manipulation. This universal design allows a single structural element to perform multiple critical functions, improving tunability without proportionally increasing device complexity.
3Ease of manufacture
If qubits are implemented on SOI technology, then manufacturing is simplified, but charge noise at the buried oxide interface increases
Solution Approach 1:
The quantum dot wavefunction is extracted or moved away from the noisy buried oxide interface by utilizing the fin structure that extends vertically from the substrate. The bottom corner gates positioned at the fin corners allow control of quantum dots that are spatially separated from the interface, extracting the qubit system from the harmful noise environment while maintaining SOI manufacturing benefits.
Solution Approach 2:
The fin structure acts as an intermediary between the buried oxide substrate and the quantum dot system. The fin material provides a clean interface for quantum dot formation while physically separating the qubits from the noisy buried oxide, mediating between the manufacturing simplicity of SOI and the need to reduce charge noise exposure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves qubit coherence by tuning the wavefunction away from noisy interfaces, facilitates better tunability, and allows for higher device density with integrated ESR drive lines, enhancing qubit performance and integration capabilities.
Implementation Method 1
The isolated bottom corner gates are used to apply electric potential, electric field, magnetic field, and alternate current (AC) electromagnetic fields to drive spin-qubits in a fin
Implementation Method 2
the first and second gates may conduct alternate currents (AC) to generate a magnetic field to drive the qubit
Implementation Method 3
Different electrical potentials may be applied to the first and second gates to apply an electric field to tune a frequency or a coupling strength of the qubit
Implementation Method 4
the first gate provides local control of the qubit and the second gate is a drive line along the fin for electron spin resonance (ESR)
Data Source
AI summary
A qubit device or system having isolated bottom corner gates includes a semiconductor substrate and a semiconductor fin perpendicularly adjoining a top surface of the substrate. The qubit device also includes a first gate located at a first corner between a first side of the fin and the top surface of the substrate, and a second gate located at a second corner between a second, opposite side of the fin and the top surface of the substrate. The first and second gates are electrically isolated from each other and used to control a first quantum dot near the top of the fin. A third gate located at the first corner has a contact for accumulating a channel to facilitate charge transport to and from a second quantum dot located near the bottom of the fin accumulated using the first and second gates.