Qubit Input Filter Notches for Fast Gates and Longer Coherence
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Solution Overview
Problem
In quantum computers using superconducting qubits, there is a trade-off between reducing the gating time and increasing the quantum coherence time, as stronger coupling between the qubit and waveguide speeds up operations but shortens coherence, leading to radiation loss and reduced data retention.
Innovation Solution
A quantum device with a filter having notches in a lower frequency band to correct signal levels for one-qubit and two-qubit gating, utilizing a highpass filter with different coupling efficiencies in distinct frequency bands to maintain quantum logic gate operations while minimizing radiation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the coupling between the qubit and waveguide is strengthened to reduce gating time, then the quantum coherence time becomes shorter due to increased radiation loss
Solution Approach 1:
The patent applies local quality by designing the waveguide with position-dependent coupling characteristics. Specifically, the coupling strength between the waveguide and qubit varies along the waveguide length, with stronger coupling in regions where fast gating is needed and weaker coupling where coherence preservation is critical. This spatially varying coupling profile allows simultaneous optimization of both gating speed and coherence time.
Solution Approach 2:
The patent employs dynamic control of coupling strength through time-varying parameters. The coupling between waveguide and qubit is modulated dynamically during different stages of the gating operation, enabling strong coupling during the gating pulse for fast operations and weak coupling during idle periods to preserve quantum coherence and minimize radiation loss.
2Productivity
If the intensity of the signal input to the control qubit is increased to speed up two-qubit gating, then the radiation loss from the control qubit to the input waveguide increases and coherence time is shortened
Solution Approach 1:
The patent introduces an intermediary mechanism through the specially designed waveguide structure that mediates the interaction between the control qubit and input signal. The waveguide acts as a controlled interface, allowing strong signal coupling for fast two-qubit gating while its engineered impedance profile and coupling regions prevent excessive radiation loss, thus maintaining coherence time despite high signal intensity requirements.
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 allows for faster quantum gating while preserving coherence time, reducing power consumption, and stabilizing operations by equalizing signal power across frequency bands, thus enhancing the performance of quantum logic gates.
Implementation Method 1
a filter having a plurality of notches in a first frequency band lower than a second frequency band
Implementation Method 2
a first qubit that resonates in the first frequency band; and a second qubit that resonates in the second frequency band
Implementation Method 3
the first qubit is input with a signal having a frequency at which the first qubit resonates via the filter to control a state of the first qubit
Data Source
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AI summary
A quantum device includes a filter having a plurality of notches in a first frequency band lower than a second frequency band, a first qubit that resonates in the first frequency band, and a second qubit that resonates in the second frequency band. The first qubit is input with a signal having a frequency at which the first qubit resonates via the filter to control a state of the first qubit when executing a one-qubit gating, and is input with a signal having a frequency at which the second qubit resonates via the filter to control a state of the second qubit according to a quantum state of the first qubit when executing a two-qubit gating.