Quantum Dot Qubit Layout Using Alternating Out-of-Plane Nanomagnets
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Solution Overview
Problem
Current semiconductor quantum dot qubit technologies face challenges in scalability due to weak spin-orbit coupling, which hinders efficient Electric Dipole Spin Resonance (EDSR) and introduces unpredictability in qubit resonant frequencies.
Innovation Solution
A qubit device design featuring a semiconductor substrate with electrostatically confined quantum dots and strategically arranged nanomagnets, where every other quantum dot is subjected to an out-of-plane magnetic field, allowing for selective qubit spin resonance frequency shifting and mitigating spin-orbit coupling, enabling scalable and efficient qubit control and readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If on-chip micromagnets are incorporated to create spatially variable in-plane spin-electric-field-coupling field, then EDSR can be supported, but device area efficiency deteriorates
Solution Approach 1:
The patent transitions from in-plane magnetic field configuration to out-of-plane magnetic field configuration. By orienting the magnetization of nanomagnets perpendicular to the quantum dot plane, the invention achieves spin-electric-field coupling without requiring in-plane magnetic field gradients, thereby reducing the area occupied by magnetic field-generating structures while maintaining EDSR functionality.
Solution Approach 2:
The patent applies out-of-plane magnetic fields locally at specific quantum dot positions using strategically placed nanomagnets. This localized approach allows selective addressing of individual qubits or subsets of qubits without requiring global in-plane field gradients across the entire device, improving area efficiency while enabling precise qubit control.
2Productivity
If conventional ESR is used for qubit control, then scalability is maintained, but control efficiency and complexity deteriorate
Solution Approach 1:
The patent replaces the magnetic field-based ESR control mechanism with an electric field-based EDSR control mechanism enabled by out-of-plane nanomagnet fields. This substitution allows qubit manipulation through electric fields from control gates, which can be more efficiently generated and modulated, reducing control complexity while improving scalability.
3Adaptability or versatility
If in-plane magnetic field is used at quantum dots, then spin-orbit coupling is present, but qubit resonant frequency predictability deteriorates
Solution Approach 1:
The patent extracts or removes the in-plane magnetic field component that causes unwanted spin-orbit coupling and frequency unpredictability. By using only out-of-plane magnetic fields from nanomagnets, the invention eliminates the harmful in-plane field effects while retaining the beneficial spin control capabilities, thereby improving resonant frequency predictability.
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
The design facilitates scalable multi-qubit systems with area-efficient quantum dots, allowing for selective qubit control and readout, reducing unpredictability in resonant frequencies and enhancing the efficiency of qubit operations.
Implementation Method 1
every other quantum dot is subjected to an out-of-plane magnetic field generated by a respective nanomagnet, such that a qubit spin resonance frequency of every other quantum dot is shifted with respect to an adjacent quantum dot
Implementation Method 2
a set of control gates configured to define a row of electrostatically confined quantum dots along the substrate layer, each quantum dot being suitable for holding a qubit
Data Source
AI summary
According to an aspect of the present inventive concept there is provided a qubit device comprising: a semiconductor substrate layer; a set of control gates configured to define a row of electrostatically confined quantum dots along the substrate layer, each quantum dot being suitable for holding a qubit; and a set of nanomagnets arranged in a row over the substrate layer such that a nanomagnet is arranged above every other quantum dot of the row of quantum dots, wherein each nanomagnet has an out-of-plane magnetization with respect to the substrate layer and wherein every other quantum dot is subjected to an out-of-plane magnetic field generated by a respective nanomagnet, such that a qubit spin resonance frequency of every other quantum dot is shifted with respect to an adjacent quantum dot of the row of quantum dots.