Ancilla Qubits Compensate Background Susceptibility in Quantum Processors
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Solution Overview
Problem
Quantum processors face errors due to background susceptibility, which arises from indirect communicative coupling between qubits, leading to loss of fidelity and sub-optimal solutions, especially in problems involving large clusters of qubits.
Innovation Solution
The method involves employing existing hardware in the quantum processor, specifically using ancilla qubits, to compensate for background susceptibility errors. This is done by embedding a problem graph into a hardware graph and setting ancilla qubits to compensate for error without contributing to the solution, or by using ancilla qubits to adjust biases and couplings to mitigate error effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If quantum processors use indirect communicative coupling between qubits, then device complexity is reduced, but background susceptibility errors increase leading to loss of fidelity
Solution Approach 1:
The patent introduces ancilla qubits as intermediary elements that mediate between problem qubits. These ancilla qubits are specifically designed to compensate for background susceptibility errors by establishing controlled direct couplings that counteract the harmful indirect coupling effects, thereby maintaining solution fidelity while preserving the overall indirect coupling architecture
Solution Approach 2:
The patent applies local quality by making different qubits serve different functions: problem qubits handle computational tasks while ancilla qubits handle error compensation. The coupling strengths are locally optimized, with specific ancilla qubits coupled to specific problem qubit pairs at controlled strengths to针对性地 compensate for their particular background susceptibility issues
2Measurement precision
If ancilla qubits are added to compensate for background susceptibility, then solution accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements partial action by introducing only the minimum necessary ancilla qubits to compensate for background susceptibility errors in critical problem qubit pairs. Rather than adding ancilla qubits to all possible pairs, the method selectively applies error compensation only where background susceptibility significantly impacts solution accuracy, thus improving accuracy while limiting the increase in device complexity
3Reliability
If direct couplings are strengthened to reduce error, then background susceptibility compensation improves, but h/J ratio imbalance increases causing bit flip errors
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the coupling strength between ancilla qubits and problem qubits during the annealing process. The coupling strength is modulated as a time-dependent parameter that starts strong to provide error compensation and gradually decreases to minimize interference with the problem Hamiltonian, thus preventing bit flip errors while maintaining reliability
Solution Approach 2:
The patent introduces dynamics by making the ancilla-problem qubit coupling time-dependent rather than static. The coupling strength evolves during the quantum annealing process, being stronger at early stages when error compensation is most needed and weakening as the system approaches the final state, thereby adapting to the changing requirements of the computation
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 effectively reduces the impact of background susceptibility errors, improving the accuracy and precision of solutions generated by the quantum processor, especially for problems sensitive to these errors.
Implementation Method 1
Josephson tunneling is the process by which Cooper pairs cross an interruption, such as an insulating gap of a few nanometers, between two superconducting electrodes
Implementation Method 2
Flux is quantized via the Aharonov-Bohm effect where electrical charge carriers accrue a topological phase when traversing a conductive loop threaded by a magnetic flux
Implementation Method 3
Superconducting qubits, whose properties can be engineered, play the role of artificial atoms
Implementation Method 4
a plurality of coupling devices, wherein each coupling device is operable to provide controllable communicative coupling between two of the plurality of qubits
Data Source
AI summary
The systems, devices, articles, and methods described herein generally relate to analog computers, for example quantum processors comprising qubits, couplers, and, or cavities. Analog computers, for example quantum processor based computers, are the subject of various sources of error which can hinder operation, potentially reducing computational accuracy and speed. Sources of error can be broadly characterized, for example as i) a background susceptibility do to inherently characteristics of the circuitry design, ii) as an h/J ratio imbalance, iii) bit flip errors, iv) fidelity, and v) Anderson localization, and various combinations of the aforesaid.