Superconducting DAC Arrays Using Kinetic Inductance for Qubit Control
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Solution Overview
Problem
Current superconducting quantum processors face challenges with scalability due to the complexity of qubit parameter control systems, particularly in managing large numbers of qubits, and existing digital-to-analog converters (DACs) are limited by size, crosstalk, and sensitivity to fabrication variability, which hinders efficient processing and readout operations.
Innovation Solution
The implementation of quantum flux parametron (QFP)-based shift registers and digital-to-analog converters (DACs) that utilize kinetic inductance for energy storage, allowing for more efficient and scalable qubit parameter control by reducing thermal noise and increasing bandwidth, enabling faster programming and readout of qubits without power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DACs are used in superconducting quantum processors, then the system can perform digital-to-analog conversion, but the DAC size increases leading to crosstalk and sensitivity to fabrication variability
Solution Approach 1:
The conventional large DAC is divided into multiple smaller DACs. Each small DAC handles a portion of the control signals for qubit parameters. This segmentation reduces the size of individual DACs, minimizing crosstalk and fabrication variability sensitivity while maintaining the ability to control multiple qubit parameters through coordinated operation of the DAC array.
Solution Approach 2:
The patent transitions from a single large DAC to a two-dimensional array of small DACs. This spatial distribution across multiple dimensions allows the system to maintain the functional capability of a large DAC while reducing the physical footprint and inter-element crosstalk of individual components.
2Productivity
If more qubits are added to increase processing power, then computational capability improves, but the complexity of qubit parameter control systems increases
Solution Approach 1:
The array of small DACs is designed to universally control multiple qubit parameters (flux, charge, phase) across many qubits. Each DAC in the array can be configured to control different parameters of different qubits, providing a scalable universal control interface that doesn't require separate control systems for each additional qubit.
Solution Approach 2:
The system uses parameter changes in the DAC array configuration to adapt to different numbers of qubits. By dynamically adjusting which DACs are active and how they are configured, the control system can scale to accommodate varying numbers of qubits without requiring a complete redesign of the control architecture.
3Measurement precision
If conventional DACs are used, then digital control signals can be converted to analog, but thermal noise and power dissipation limit performance
Solution Approach 1:
The patent replaces conventional electronic DAC mechanisms with superconducting quantum interface device (SQUID)-based DACs. These superconducting DACs operate without resistive heating, eliminating the thermal noise and power dissipation problems inherent in conventional electronic DACs. The SQUID-based conversion mechanism uses quantum effects rather than classical electronic resistance, fundamentally changing the noise characteristics.
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 enhances the scalability and performance of quantum processors by reducing thermal noise, improving control precision, and enabling faster programming and readout operations, facilitating the operation of quantum processors with a large number of qubits while minimizing thermal load and fabrication noise.
Implementation Method 1
a number M of Josephson junctions, where M is greater than N
Implementation Method 2
Each loop has a respective storage inductance
Data Source
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AI summary
Approaches useful to operation of scalable processors with ever larger numbers of logic devices (e.g., qubits) advantageously take advantage of QFPs, for example to implement shift registers, multiplexers (i.e., MUXs), de-multiplexers (i.e., DEMUXs), and permanent magnetic memories (i.e., PMMs), and the like, and/or employ XY or XYZ addressing schemes, and/or employ control lines that extend in a "braided" pattern across an array of devices. Many of these described approaches are particularly suited for implementing input to and/or output from such processors. Superconducting quantum processors comprising superconducting digital-analog converters (DACs) are provided. The DACs may use kinetic inductance to store energy via thin-film superconducting materials and/or series of Josephson junctions, and may use single-loop or multi-loop designs. Particular constructions of energy storage elements are disclosed, including meandering structures. Galvanic connections between DACs and/or with target devices are disclosed, as well as inductive connections.