Persistent Flux Biasing in Superconducting Loops for Stable Qubits
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Solution Overview
Problem
Superconducting qubits are sensitive to noise from external flux bias lines, leading to dephasing and reduced coherence, which limits their effectiveness in quantum processors.
Innovation Solution
A tunable qubit device with a superconducting loop inductively coupled to a SQUID loop and a flux bias line, where the superconducting loop provides a persistent magnetic field by trapping flux using controlled temperature changes, isolating the qubit from noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If persistent flux biasing is applied to stabilize qubit flux states, then qubit stability and coherence are improved, but magnetic flux noise and interference increase
Solution Approach 1:
The biasing system is divided into multiple independent superconducting loops (first loop and second loop) that can be controlled separately. This segmentation allows the patent to apply biasing fields to stabilize qubit states while using independent control to manage and minimize magnetic flux noise from each loop individually.
Solution Approach 2:
The patent introduces an intermediary mechanism where the superconducting loops act as mediators between the control system and the qubit. These loops provide the necessary magnetic flux biasing while their superconducting nature and configurable design allow them to filter and control the magnetic flux, reducing harmful noise transmission to the qubit.
2Measurement precision
If multiple superconducting loops are used for flux biasing, then qubit control precision is improved, but device complexity increases
Solution Approach 1:
The superconducting loops are designed to perform multiple functions: they provide persistent flux biasing, enable qubit state control, and serve as part of the readout mechanism. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving precise flux control through the configurable loop parameters.
3Stability of the object's composition
If persistent current is maintained in superconducting loops, then flux bias stability is improved, but energy consumption and system overhead increase
Solution Approach 1:
The patent utilizes the superconducting phase transition to maintain persistent currents without energy dissipation. By operating the loops in the superconducting state, the system achieves stable flux biasing through persistent currents that flow without resistance, eliminating continuous energy consumption while maintaining composition stability.
Solution Approach 2:
The superconducting loops maintain their persistent currents through self-service mechanisms where the circulating current generates its own magnetic field without requiring external power supply. This self-sustaining property provides stable flux biasing while minimizing energy overhead, as the system only requires initial current establishment and maintains itself through the superconducting state.
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
The persistent biasing method enhances qubit coherence by maintaining a stable magnetic field without noise interference, allowing for precise frequency tuning and extended operation.
Implementation Method 1
a superconducting loop inductively coupled to the SQUID loop, and a flux bias line inductively coupled to the superconducting loop
Implementation Method 2
The superconducting loop is formed from a superconducting material having a critical temperature that is a lower temperature than a critical temperature of any superconducting material of the tunable qubit
Data Source
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AI summary
A tunable qubit device includes a tunable qubit, the tunable qubit including a superconducting quantum interference device (SQUID) loop. The tunable qubit device further includes a superconducting loop inductively coupled to the SQUID loop, and a flux bias line inductively coupled to the superconducting loop. The superconducting loop includes a superconducting material having a critical temperature that is a lower temperature than a critical temperature of any superconducting material of the tunable qubit. In operation, the superconducting loop provides a persistent bias to the tunable qubit.