Microwave Pulse Generator With Phase Correction for Quantum Bits
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Solution Overview
Problem
In quantum computers using electron spins, phase errors occur due to shifts in the 90° phase difference between RF signals and misalignments in signal amplitudes, leading to inaccuracies in quantum manipulations. Additionally, frequency switching during quantum operations causes phase shifts, further complicating precise control over quantum bits.
Innovation Solution
A microwave pulse generator is designed with a logic circuit, frequency generator, converter, and frequency divider to output microwave pulses with precise phase control. The system includes mechanisms to correct phase shifts caused by frequency switching and reduce phase errors between quantum bits and microwave pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an IQ modulator is used to control phase by changing RF signal amplitudes, then phase control capability is improved, but phase errors occur due to shifts in 90° phase difference and misalignments in signal amplitudes
Solution Approach 1:
The patent introduces a phase correction mechanism that acts as an intermediary between the IQ modulator and the quantum bit. A phase correction value is calculated based on the relationship between the microwave pulse phase and the quantum bit phase, then applied to correct the phase error. This mediator component resolves the contradiction by maintaining ease of phase control while improving phase accuracy through active correction.
Solution Approach 2:
The system implements feedback by continuously monitoring the phase relationship between microwave pulses and quantum bits, calculating phase correction values, and applying corrections in subsequent operations. This feedback loop ensures that phase errors are detected and corrected, maintaining high phase accuracy while preserving the operational simplicity of the IQ modulator approach.
2Adaptability or versatility
If frequency switching is performed to operate on different quantum bits, then versatility is improved, but phase shifts occur in the microwave pulse output
Solution Approach 1:
The patent applies preliminary action by calculating the phase correction value in advance, before the actual quantum manipulation occurs. The correction value is computed based on the frequency switching operation that is about to take place, and this pre-calculated correction is then applied to prevent phase shifts. This approach maintains versatility in quantum bit selection while preserving phase stability.
Solution Approach 2:
The system performs preliminary anti-action by introducing a counteracting phase correction that opposes the expected phase shift caused by frequency switching. Before the frequency switching affects the quantum operation, the correction mechanism applies an equal and opposite phase adjustment, thereby preventing the harmful phase shift while maintaining the ability to switch between different quantum bits.
3Productivity
If multiple quantum bits are operated simultaneously with spatially spread microwave pulses, then productivity is improved, but control precision over individual quantum bits deteriorates
Solution Approach 1:
The patent applies local quality by tailoring the phase correction to each individual quantum bit being operated. Even when multiple quantum bits are processed simultaneously, each quantum bit receives a customized phase correction value calculated based on its specific frequency and phase relationship with the microwave pulse. This ensures that control precision for individual quantum bits is maintained while allowing high productivity through parallel operations.
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 solution effectively corrects phase shifts due to frequency switching and minimizes phase errors, thereby enhancing the accuracy of quantum manipulations during the coherence time of quantum bits.
Implementation Method 1
a frequency generator that outputs a sine wave having the same frequency as the selected quantum bit
Implementation Method 2
a converter that converts the pulse data into an analog signal, modulates it with the sine wave, and outputs a signal having the frequency of the sine wave as the center frequency as a microwave pulse
Implementation Method 3
a frequency divider that outputs a system clock divided by the frequency of the sine wave, wherein the frequency generator operates at the same frequency as the quantum bit other than the selected quantum bit except when the microwave pulse is output, and the logic circuit operates in synchronization with the system clock
Data Source
AI summary
The microwave pulse generator 101 consists of a logic circuit 203 that outputs pulse data 213 of a set pulse width and amplitude, a frequency generator 201 that outputs sine waves 211, 212 having the same frequency as the selected quantum bit, a RFDAC 204 that converts pulse data 213 into an analogue signal, modulates it with a sine wave 211 and outputs a signal with the frequency of the sine wave as the center frequency as microwave pulse 111, and a frequency divider 202 that outputs system clock 124 divided by the frequency of sine wave 212. The frequency generator 201 operates at the same frequency as the selected quantum bit except when outputting microwave pulse 111, and the logic circuit 203 operates in synchronization with the system clock 124.