Josephson-Junction Quantum Filter Tuning for Multi-Qubit Crosstalk
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Solution Overview
Problem
The challenge of integrating filtering circuits on quantum chips with a large number of qubits without excessive spatial overhead and minimizing frequency crosstalk between resonant cavities is unresolved, as existing methods either occupy too much space or result in poor filtering effects due to frequency offset and inadequate bandwidth coverage.
Innovation Solution
A quantum chip parameter determination method and device that utilizes a filter comprising a coplanar waveguide with parallel Josephson junctions and input coupling capacitors, where the center frequency and bandwidth are adjusted by modifying the length and inductance of the Josephson junctions to encompass all resonant cavity frequency bands, allowing for efficient filtering without increasing space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple qubits share a bandpass filter to save space, then spatial overhead is reduced, but frequency crosstalk between resonators becomes more pronounced
Solution Approach 1:
The patent applies dynamics by making the filter's center frequency adjustable through voltage control of the varactor diode. This allows the filter to dynamically adapt its frequency response to match different qubit resonant frequencies, reducing frequency crosstalk while maintaining shared filter architecture. The voltage-tunable capacitance enables real-time frequency adjustment without physical reconfiguration.
Solution Approach 2:
The patent changes the electrical parameter (capacitance) of the filter by incorporating voltage-tunable varactor diodes. By adjusting the bias voltage applied to the varactor diodes, the filter's center frequency and bandwidth can be dynamically modified to optimize performance for different qubit frequencies, thereby reducing frequency crosstalk while maintaining spatial efficiency.
2Object-affected harmful factors
If the filter's frequency band coverage is reduced to minimize crosstalk, then frequency selectivity improves, but the filter cannot cover the entire required frequency range
Solution Approach 1:
The patent implements dynamics by enabling the filter to dynamically adjust its center frequency through voltage control. This allows a single filter to adaptively cover different frequency ranges by tuning the varactor diode capacitance, maintaining both frequency selectivity (to reduce crosstalk) and broad coverage (to support multiple qubits with different frequencies).
Solution Approach 2:
The patent achieves universality by designing a voltage-tunable filter that can serve multiple qubits with different resonant frequencies. The filter's frequency response can be reconfigured via voltage control to match any target qubit frequency within the operating range, making a single filter component universally applicable to multiple qubits rather than requiring dedicated filters for each.
3Object-affected harmful factors
If a filter is designed with narrow bandwidth to improve filtering effect, then frequency selectivity increases, but the filter cannot effectively filter multiple resonant cavity frequencies
Solution Approach 1:
The patent applies dynamics by making the filter bandwidth adjustable through voltage control of the varactor diodes. The filter can dynamically narrow its bandwidth to improve filtering effect for a specific qubit frequency, then broaden and shift its response to cover other frequencies. This temporal separation of narrowband filtering for different frequencies resolves the contradiction between narrow bandwidth and multi-frequency coverage.
Solution Approach 2:
The patent implements periodic action by sequentially tuning the filter to different frequency bands to service multiple qubits. The filter alternates between narrowband modes for different qubit frequencies, with each tuning cycle providing optimized filtering for one qubit while maintaining the capability to switch to other frequencies, achieving both narrow bandwidth benefits and multi-frequency support.
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 enables effective filtering across multiple qubits with reduced spatial requirements and improved frequency coverage, maintaining qubit lifetimes by minimizing energy leakage and crosstalk, thus enhancing quantum chip performance.
Implementation Method 1
the filter includes a coplanar waveguide, at least one pair of parallel Josephson junctions, and an input coupling capacitor; the coplanar waveguide is coupled to the readout line; the Josephson junctions are disposed on the coplanar waveguide
Data Source
AI summary
The disclosure provides a quantum chip parameter determination method and device, and a filtering regulation method and device, relates to the field of quantum chips, to address the problem that a large amount of space in quantum chips are occupied in order to meet the filtering function of the quantum chips having a large number of qubits; wherein Josephson junctions are provided on the coplanar waveguide of the filter, and adjusting the critical current of the Josephson junctions and changing the equivalent inductances corresponding to the filter enables regulating the center frequency of the filter; the initial length that meets the center frequency range and bandwidth range, as well as the inductance set are selected, so that the Josephson junctions can, during regulation, cover the frequencies required by all resonant cavities, encompassing all resonant cavity frequency bands through one filter.