Silicon Electron Spin Qubit Arrays for High-Density Quantum Computing

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Solution Overview

Problem

Current quantum computers face challenges in high integration, mounting limitations, low qubit fidelity, and noise susceptibility, particularly due to the large size of superconducting qubits and the need for extremely low temperatures, which complicates the integration of large-scale qubits and increases noise vulnerability.

Innovation Solution

A silicon electron spin-based quantum computer design that uses smaller qubits (100 nm sq.) integrated in arrays, with a read circuit that improves noise resistance and fidelity by performing parallel computations and statistical averaging of results across multiple qubit blocks, reducing the number of control signals and enhancing computation accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If superconducting transmon qubits are used, then quantum computation can be performed, but the qubit size becomes large (about 100 um sq.) which limits high integration

Engineering Contradiction:
Improvequantum computation capabilityVSAvoidqubit size
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces superconducting transmon qubits with silicon electron spin qubits, substituting a different physical mechanism (electron spin in quantum dots) for the previous mechanism (superconducting circuits). This substitution enables significantly smaller qubit footprint while maintaining quantum computation capability, directly resolving the contradiction between computation reliability and qubit size.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If large-scale qubits are integrated, then computation capacity increases, but the number of control signals increases which decreases cooling capacity and makes it difficult to maintain extremely low temperature

Engineering Contradiction:
Improvecomputation capacityVSAvoidnumber of control signals
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the qubit array into multiple blocks of 4 qubits each, with each block sharing common control lines. This segmentation strategy reduces the total number of control signals required from O(N) to O(N/4) while maintaining the ability to perform computations on all qubits, thereby resolving the contradiction between computation capacity and control signal complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements multi-functional control lines that can address multiple qubit blocks simultaneously. The same control lines used for initializing qubits in one block can be reused for operations in other blocks, making the control system more efficient and reducing the overall number of required control signals while maintaining full computation capacity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Reliability

If qubits operate at extremely low temperature to eliminate noise influence, then computation fidelity improves, but the physical restrictions on integration increase and cooling capacity decreases

Engineering Contradiction:
Improvecomputation fidelityVSAvoidphysical restrictions on integration
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent substitutes superconducting qubits with silicon electron spin qubits that can operate at higher temperatures. This substitution relaxes the extreme temperature requirements, thereby reducing physical restrictions on integration while maintaining computation fidelity, as electron spin qubits in silicon quantum dots have longer coherence times and are less sensitive to thermal noise than superconducting qubits.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Productivity

If qubits are used to perform quantum computations, then computation can be executed, but qubits are extremely vulnerable to disturbances from outside such as electromagnetic fields and vibration which causes fidelity to decrease

Engineering Contradiction:
Improvecomputation executionVSAvoidvulnerability to electromagnetic fields and vibration
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces superconducting qubits with silicon electron spin qubits that are inherently more resistant to external disturbances. Electron spin qubits in silicon quantum dots are protected by the strong spin-orbit coupling and can be isolated from electromagnetic field disturbances, thereby reducing vulnerability to harmful factors while maintaining computation execution capability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements error correction codes and redundancy mechanisms that provide beforehand protection against disturbances. By preparing multiple qubit blocks and implementing statistical averaging of results, the system can compensate for errors caused by electromagnetic field disturbances and vibration before they affect the final computation outcome, thereby cushioning against harmful factors.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP3896623A1Silicon electron spin type massively parallel quantum computer
Publication Date: 2021.10.20 HITACHI LTD
  • EP3896623A1 patent drawingFigure 1
  • EP3896623A1 patent drawingFigure 2
  • EP3896623A1 patent drawingFigure 3

AI summary

A quantum computer includes: a module including quantum computation units having a plurality of qubits and selection units that cause the quantum computation units to perform parallel computations; and a read unit that acquires computation results of the quantum computation units of a plurality of modules and performs statistical averaging on the plurality of acquired computation results.