Hybrid Quantum-Classical QUBO Optimization via Segmented Iteration

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Solution Overview

Problem

Current computational methods face challenges in efficiently solving quadratic unconstrained binary optimization (QUBO) problems, which are crucial in fields like machine learning and data compression, due to the complexity of optimizing both Boolean weights and dictionaries simultaneously.

Innovation Solution

The method involves casting the sparse least squares problem as a QUBO problem suitable for quantum processors, using a combination of adiabatic quantum computation and quantum annealing to minimize the objective function by alternating between optimizing Boolean weights and dictionary updates, leveraging the strengths of both quantum and non-quantum processors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If classical computational methods are used to solve QUBO problems, then the problem can be addressed with existing hardware, but the optimization of both Boolean weights and dictionaries simultaneously becomes computationally intractable and time-consuming

Engineering Contradiction:
Improveoptimization speedVSAvoidcomputational complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the optimization process into two distinct phases: a quantum phase for optimizing Boolean weights and a classical phase for updating dictionaries. This segmentation allows each phase to be handled by the most suitable computational approach, with the quantum processor handling the combinatorial optimization and the classical processor handling the linear algebra operations, thereby reducing overall computational complexity and time.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary interface between quantum and classical processors that enables iterative exchange of data and control signals. The quantum processor receives dictionary information from the classical processor, performs weight optimization, and returns updated weights, which are then used to update the dictionary. This intermediary coordination mechanism enables hybrid optimization that leverages the strengths of both computational paradigms.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Productivity

If quantum processors are used to solve QUBO problems, then optimization efficiency improves, but the ability to handle continuous dictionary updates and iterative optimization becomes more complex

Engineering Contradiction:
Improveoptimization efficiencyVSAvoidoperational complexity
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

The patent divides the operational complexity between two processors: the quantum processor handles discrete weight optimization with clear input-output interfaces, while the classical processor manages continuous dictionary updates using standard linear algebra operations. This segmentation simplifies the operational interface for each processor type, making the overall system easier to implement despite the hybrid nature of the computation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements feedback mechanisms where the quantum processor's weight optimization results feed back into the classical processor for dictionary updates, and the updated dictionary then feeds back to the quantum processor for the next iteration of weight optimization. This feedback loop enables iterative refinement of both weights and dictionaries, making the system adaptable to different problem instances while maintaining operational clarity through standardized interaction protocols.

Inventive Principle:
Principle #23Feedback

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

This approach enables efficient convergence of solutions for QUBO problems, effectively solving sparse least squares and data compression tasks by leveraging the strengths of quantum processors in minimizing the objective function through iterative optimization.

Implementation Method 1

Adiabatic quantum computation typically involves evolving a system from a known initial Hamiltonian to a final Hamiltonian by gradually changing the Hamiltonian

Methodology Applied
Scientific EffectAdiabatic evolution:

Implementation Method 2

Quantum annealing is a computation method that may be used to find a low-energy state, typically preferably the ground state, of a system

Methodology Applied
Scientific EffectQuantum annealing: Annealing

Implementation Method 3

quantum annealing may use quantum effects, such as quantum tunneling, to reach a global energy minimum more accurately and/or more quickly than classical annealing

Methodology Applied
Scientific EffectQuantum tunneling:

Implementation Method 4

all successful implementations generally include a superconducting loop (i.e., a 'qubit loop') that is interrupted by at least one Josephson junction

Methodology Applied
Scientific EffectJosephson effect: Josephson Effect

Implementation Method 5

integrated circuits formed of superconducting material, such as aluminum and/or niobium, to define superconducting qubits

Methodology Applied
Scientific EffectSuperconductivity: Superconductivity

Data Source

PatentUS8977576B2Methods for solving computational problems using a quantum processor
Publication Date: 2015.03.10 D WAVE SYSTEMS INC
  • US8977576B2 patent drawing
  • US8977576B2 patent drawing
  • US8977576B2 patent drawing

AI summary

Methods for solving a computational problem including minimizing an objective including a set of weights and a dictionary by casting the weights as Boolean variables and alternately using a quantum processor and a non-quantum processor to successively optimize the weights and the dictionary, respectively. A first set of values for the dictionary is guessed and the objective is mapped to a QUBO. A quantum processor is used to optimize the objective for the Boolean weights based on the first set of values for the dictionary by minimizing the resulting QUBO. A non-quantum processor is used to optimize the objective for the dictionary based on the Boolean weights by updating at least some of the columns of the dictionary. These processes are successively repeated until a solution criterion is met. Minimization of the objective may be used to generate features in a learning problem and/or in data compression.