Racetrack Memory Readout Using Josephson Diode Direction Sensing

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Solution Overview

Problem

Conventional memory devices, such as MRAM and RTM, face challenges in operating at low temperatures and require significant energy consumption for reading operations, while quantum computing faces scalability issues due to heat load and latency from digital control circuits. The Josephson junctions (JJs) are not sensitive to the direction of applied magnetic fields, limiting their use as reading elements in racetrack devices.

Innovation Solution

A reading element for RTMs utilizing a Josephson junction (JJ) is developed, comprising superconducting electrodes separated by a topological metal with a spin-polarized surface state, such as NiTe2, which exhibits a band inversion, allowing the critical current to be modulated by an external magnetic field, enabling high-speed, low-dissipation reading.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional Josephson junctions are used as reading elements, then high-speed operation in the sub-THz regime is achieved, but the junctions are not sensitive to the direction of applied magnetic fields

Engineering Contradiction:

Improvereading speedVSAvoidmagnetic field direction sensitivity

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent introduces a magnetic field gradient across the Josephson junction, creating an asymmetric condition that breaks the symmetry of the junction's response to magnetic fields. This asymmetric magnetic field distribution enables the junction to distinguish between different magnetic field directions while maintaining its high-speed superconducting operation, thus resolving the contradiction between speed and directional sensitivity.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent employs a magnetic field gradient as an intermediary mechanism that couples the superconducting junction to the magnetic field direction information. This gradient acts as a mediator that translates magnetic field direction into a detectable signal at the junction, enabling directional sensitivity without compromising the junction's inherent high-speed superconducting properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If superconducting materials are used to increase read-out speed, then resistance is minimized and speed is maximized, but energy consumption for cooling increases

Engineering Contradiction:

Improveread-out speedVSAvoidcooling energy consumption

Core Design Contradiction:

SpeedVSUse of energy by stationary object

Solution Approach 1:

The patent utilizes the Josephson junction's inherent superconducting properties to achieve high-speed read-out operations without requiring external cooling systems. The junction's superconducting state naturally provides low resistance and high speed, allowing the device to serve its own cooling needs through the quantum mechanical effects inherent in the superconducting material, thereby eliminating the need for energy-intensive cryogenic cooling infrastructure.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If the number of qubits is scaled up, then quantum computing capability increases, but heat load and wiring complexity increase significantly

Engineering Contradiction:

Improvequantum computing capabilityVSAvoidwiring complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent designs a universal reading element based on the Josephson junction that can serve multiple functions: reading quantum state information, performing logic operations, and interfacing with classical control circuits. This multi-functional design eliminates the need for separate dedicated reading components for each qubit, thereby reducing wiring complexity while maintaining the ability to scale quantum computing capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 device achieves high-speed reading operations in the sub-THz regime with low heat dissipation, as the critical current varies with magnetic field direction, facilitating efficient data retrieval in racetrack memories.

Implementation Method 1

a junction formed from two superconducting electrodes separated by a non-superconducting barrier becomes superconducting, and the critical current of this junction can be modulated by altering the phase difference between the respective wave functions across the junction

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Implementation Method 2

separated by a topological metal (N) with a spin-polarized surface state, which exhibits a band inversion

Methodology Applied

Scientific EffectSpin-polarized surface state:

Implementation Method 3

which exhibits a band inversion, preferably a two-dimensional, centrosymmetric, type-II, Dirac semi-metal

Methodology Applied

Scientific EffectBand inversion:

Data Source

PatentUS20250285695A1Racetrack Memory Reading Device based on Josephson Diode Effect

Publication Date: 2025.09.11 MAX PLANCK GESELLSCHAFT ZUR FOERDERUNG DER WISSENSCHAFTEN EV

AI summary

The present invention relates to a reading element for a racetrack memory (RTM) that includes two superconducting electrodes (S) made of a superconducting material, which electrodes are separated by a topological metal (N) with a spin-polarized surface state, which exhibits a band inversion. The invention further relates to a method of making such a reading element as well as to its use, specifically in a racetrack memory.