Phase-Biased Superconducting Qubits With High Anharmonicity
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Solution Overview
Problem
Current superconducting qubits, such as fluxoniums and 0-π-qubits, face challenges with short coherence times and low anharmonicity, making them unsuitable for fast and accurate quantum logic gates due to noise sensitivity and complex implementation.
Innovation Solution
A quantum processing unit is designed with phase-biased linear and non-linear inductive-energy elements, where the quadratic potential energy terms are partly cancelled, increasing anharmonicity and reducing noise sensitivity, using geometric inductors, Josephson junctions, and capacitive-energy elements on a dielectric substrate, with magnetic flux control and coupling resonators for flexible qubit manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluxonium qubits are used to achieve long coherence times, then immunity to charge noise is improved, but implementation complexity and difficulty of operation increase
Solution Approach 1:
The qubit design segments the inductive energy storage into two distinct components: a linear inductive-energy element (geometric inductor) and a non-linear inductive-energy element (Josephson junction). This segmentation allows each element to be optimized independently for its specific function while working together to achieve the overall goal of high coherence and high anharmonicity.
Solution Approach 2:
The invention changes the parameters of the potential energy landscape by introducing a phase-biasing element that biases the superconducting phase difference. This parameter change causes the quadratic potential energy terms of the linear and non-linear inductive elements to cancel, transforming the energy spectrum to achieve high anharmonicity while maintaining long coherence times.
2Speed
If charge qubits are used to achieve high anharmonicity for fast operations, then single-qubit operation speed is improved, but coherence time decreases due to charge noise sensitivity
Solution Approach 1:
The invention introduces a phase-biasing element as an intermediary component that mediates between the linear and non-linear inductive-energy elements. This intermediary biases the superconducting phase difference to achieve cancellation of quadratic potential energy terms, enabling the system to simultaneously achieve high anharmonicity (for fast operations) and long coherence times (by being immune to charge noise through the inductive shunt).
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 design achieves high-coherence and high-anharmonicity superconducting qubits, enhancing processing speed and efficiency by minimizing dephasing from noise, particularly flux noise, and simplifying fabrication while maintaining long relaxation and coherence times.
Implementation Method 1
The linear inductive-energy element is superconductive
Implementation Method 2
The non-linear inductive-energy element comprises one or more Josephson junctions
Implementation Method 3
with magnetic flux control and coupling resonators for flexible qubit manipulation
Data Source
AI summary
A quantum processing unit is disclosed. The quantum processing unit includes at least one superconducting qubit that is based on phase-biased linear and non-linear inductive-energy elements. A superconducting phase difference across the linear and non-linear inductive-energy elements is biased, for example, by an external magnetic field, such that quadratic potential energy terms of the linear and non-linear inductive-energy elements are cancelled at least partly. In a preferred embodiment, such cancellation is at least 30%. The partial cancellation of the quadratic potential energy terms makes it possible to implement a high-coherence high-anharmonicity superconducting qubit design.