Microwave Pulse Distortion Compensation Via Standing Wave Analysis
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Solution Overview
Problem
Microwave pulse distortion in quantum computing systems due to impedance discontinuities causes control errors and reduces gate fidelity, with existing methods ineffective in compensating for reflections with short round trip times.
Innovation Solution
Characterize and compensate pulse distortion using standing wave analysis to determine reflection model parameters, pre-distort control pulses based on inverted transfer functions, and apply these pulses to qubits to reduce control errors and improve gate fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pulse delivery methods are used, then the system is simple to operate, but microwave pulse distortion due to impedance discontinuities causes control errors and reduces gate fidelity
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-applied distortion compensation to control pulses before they are sent to the qubit. The system measures the actual pulse waveform, compares it to the ideal waveform, calculates the distortion, and applies the inverse distortion as a correction factor in advance. This ensures that when the compensated pulse reaches the qubit, it has the correct shape and amplitude, eliminating control errors without requiring complex real-time adjustments during quantum operations.
2Reliability
If existing compensation methods are used, then some distortion can be addressed, but they are ineffective for reflections with short round trip times
Solution Approach 1:
The patent implements feedback by measuring the actual control pulse waveform after it has traveled through the transmission line and before it reaches the qubit. The system compares this measured waveform to the ideal waveform, calculates the distortion introduced by reflections (including short round trip time reflections), and uses this information to compute a compensation factor. This closed-loop feedback mechanism allows the system to adapt to actual reflection conditions and provide accurate compensation for both long and short round trip times, overcoming the limitations of open-loop methods.
3Reliability
If no distortion compensation is applied, then the system remains simple, but control errors increase and gate fidelity decreases
Solution Approach 1:
The patent applies parameter changes by modifying the temporal parameters of the control pulse (amplitude, phase, duration) based on measured distortion characteristics. The system calculates correction factors that adjust these parameters to compensate for reflections. By changing the pulse parameters in a controlled manner based on actual measurements, the system achieves high gate fidelity while keeping the processing system relatively simple, avoiding the need for complex real-time control mechanisms.
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 described techniques enhance quantum gate fidelity by reducing control errors through precise qubit state control, applicable to a wider range of systems with both long and short round trip times.
Implementation Method 1
The reflection model parameterize a standing wave contribution to the drive signal that modifies an effective amplitude of the drive signal incident on the qubit
Implementation Method 2
measuring the qubit to obtain measurement data that represents qubit state population after application of the drive signal; extracting, from the measurement data and for each qubit transition frequency in a subset of the multiple values of the qubit transition frequency, a minimal amplitude that corresponds to a full population transfer after application of the drive signal
Data Source
AI summary
Methods, systems and apparatus for microwave pulse distortion compensation using reflection parameters from standing wave analysis. In one aspect, a method includes generating a pre-distorted control signal that implements a single qubit rotation operation and applying the pre-distorted control signal to a qubit to perform the rotation operation on the qubit, the pre-distorted control signal comprising an inverted transfer function. The inverted transfer function comprises values of parameters obtained through fitting control pulse amplitudes that implement a full qubit population transfer to a reflection model with reflection model parameters that parameterize a standing wave contribution to the control signal that modifies an effective amplitude of control pulses incident on the qubit.