Random-Walk Phase Estimation for Low-Memory Quantum Hardware

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Solution Overview

Problem

Existing phase estimation methods for quantum computing are sub-optimal, difficult to program, require excessive classical computing resources, and are not robust to noise and decoherence, making them unsuitable for near-term quantum devices.

Innovation Solution

A deterministic random walk approach for phase estimation that uses a classical computer to cooperatively control a quantum computing device, minimizing memory requirements and executing within nanosecond timescales, with an unwinding procedure to correct for inconsistencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing phase estimation methods are used, then phase estimation can be performed, but they require excessive classical computing resources and memory

Engineering Contradiction:
Improvephase estimation accuracyVSAvoidclassical computing resources
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the essential phase estimation function from complex existing algorithms and implements it using a simplified random walk approach on quantum hardware, separating the core estimation logic from resource-intensive classical processing

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the algorithmic parameters by using a random walk-based estimation method with limited memory states instead of full quantum state simulation, reducing classical memory requirements while maintaining estimation accuracy

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If existing phase estimation methods are used, then phase estimation can be performed, but they are not robust to noise and decoherence

Engineering Contradiction:
Improvephase estimation accuracyVSAvoidrobustness to noise
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent implements feedback through iterative random walk steps where each measurement outcome influences subsequent walk directions, allowing the system to adapt and maintain accuracy despite noise and decoherence effects

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent uses dynamic random walk paths that adapt based on measurement outcomes, making the estimation process flexible and resilient to environmental noise rather than following fixed deterministic sequences

Inventive Principle:
Principle #15Dynamics

3Measurement precision

If existing phase estimation methods are used, then phase estimation can be performed, but they are difficult to program and execute

Engineering Contradiction:
Improvephase estimation accuracyVSAvoidprogramming complexity
Core Design Contradiction:
Measurement precisionVSEase of operation

Solution Approach 1:

The patent employs self-service through automated random walk generation and update mechanisms that require minimal manual programming intervention, with the system automatically adapting its estimation process based on measurement feedback

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3721386B1Using random walks for iterative phase estimation
Publication Date: 2025.07.09 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP3721386B1 patent drawingFigure 1
  • EP3721386B1 patent drawingFigure 2
  • EP3721386B1 patent drawingFigure 3

AI summary

The disclosed technology concerns example embodiments for estimating eigenvalues of quantum operations using a quantum computer. Such estimations are useful in performing Shor's algorithm for factoring, quantum simulation, quantum machine learning, and other various quantum computing applications. Existing approaches to phase estimation are sub-optimal, difficult to program, require prohibitive classical computing, and/or require too much classical or quantum memory to be run on existing devices. Embodiments of the disclosed approach address one or more (e.g., all) of these drawbacks. Certain examples work by using a random walk for the estimate of the eigenvalue that (e.g., only) keeps track of the current estimate and the measurement record that it observed to reach that point.