Quantum Annealer Flux Bias Error Compensation
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Solution Overview
Problem
Quantum annealing systems face challenges in accurately realizing time-independent Ising spin glass instances due to intrinsic and control errors, which affect the efficacy of quantum processors in solving computational problems.
Innovation Solution
The system employs a quantum processor with a plurality of qubits and coupling devices, using a time-dependent flux bias to emulate the evolution of the qubit persistent current, thereby minimizing errors in the realization of the target Hamiltonian and ensuring the processor operates independently of the system's localization state during quantum annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quantum annealing is performed without compensating for persistent current evolution, then the quantum processor can operate with simpler control mechanisms, but intrinsic and control errors increase, reducing the accuracy of realizing the target Hamiltonian
Solution Approach 1:
The system pre-calculates the evolution of qubit persistent current during quantum annealing and applies a compensating time-dependent flux bias before the annealing process begins. This preliminary compensation action ensures that the qubit energy transitions remain accurate throughout the annealing process, preventing intrinsic and control errors without requiring complex real-time adjustments during operation
Solution Approach 2:
The system implements a feedback mechanism where the evolution of qubit persistent current is monitored and compensated by adjusting the flux bias dynamically. This feedback loop ensures that the quantum processor maintains high accuracy in realizing the target Hamiltonian by continuously counteracting deviations caused by persistent current changes
2Loss of information
If all qubits are read out during quantum annealing, then complete information about the system state is obtained, but measurement time and system perturbation increase, reducing overall system performance
Solution Approach 1:
The system extracts and reads out only the essential qubits that contain the critical information needed to determine the system state and solution quality. By selectively reading out a subset of qubits rather than all qubits, the system maintains sufficient information completeness while significantly reducing measurement time and minimizing perturbation to the quantum system
Solution Approach 2:
The system performs partial readout of qubits, reading out only the necessary portion of the system state required to evaluate the solution. This partial action approach avoids the excessive time cost and perturbation associated with reading out all qubits, while still obtaining sufficient information to determine whether the ground state or a low-lying excited state was reached
Data Source
AI summary
Techniques for improving the performance of a quantum processor are described. The techniques include reading out a fraction of the qubits in a quantum processor and utilizing one or more post-processing operations to reconstruct qubits of the quantum processor that are not read. The reconstructed qubits may be determined using a perfect sampler to provide results that are strictly better than reading all of the qubits directly from the quantum processor. The composite sample that includes read qubits and reconstructed qubits may be obtained faster than if all qubits of the quantum processor are read directly.