Quantum Control Signal Generation With Arbitrary Phase Alignment
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Solution Overview
Problem
Existing methods struggle to generate phase-accurate pulses for quantum processing gates, particularly with high-frequency carriers in the GHz range, as they require high-frequency local oscillators and up-conversion, making it challenging to control the phase without imposing undesirable limits on frequencies and timing.
Innovation Solution
A signal generator with dual channels, each comprising digital sections, DACs, and up-converters, uses numerically controlled oscillators and phase shifts to generate pulses that maintain phase accuracy by adjusting phase shifts between times t0 and t1, allowing fine-grained phase control without requiring timing commensurate with frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-frequency local oscillators and up-conversion are used to generate GHz range signals, then the signal frequency capability is improved, but the phase control difficulty increases
Solution Approach 1:
The patent replaces direct analog phase control of high-frequency local oscillators with a digital control system. A digital signal generator produces baseband I/Q signals that are modulated onto the high-frequency carrier through mixing. The phase control is achieved digitally by controlling the baseband signals, avoiding the need to directly control the phase of high-frequency oscillators. This substitution of digital control for analog control at high frequencies resolves the contradiction between achieving high signal frequency and maintaining ease of phase control.
2Manufacturing precision
If repetition rates are chosen commensurate with carrier frequencies, then phase alignment between qubits and drive signals is improved, but the flexibility in frequency and timing choices is reduced
Solution Approach 1:
The patent segments the signal generation process into independent baseband signal generation and up-conversion stages. The digital signal generator produces pulses at arbitrary repetition rates independent of the carrier frequency. These baseband pulses are then modulated onto the high-frequency carrier through mixing with local oscillators. This segmentation allows the repetition rate to be chosen independently from the carrier frequency, maintaining phase alignment precision while restoring flexibility in frequency and timing choices.
Solution Approach 2:
The patent introduces baseband I/Q signals as an intermediary between the digital control system and the high-frequency carrier. Instead of directly controlling the high-frequency signal phase, the system controls the phase and timing of the baseband intermediary signals. These baseband signals then modulate the carrier through mixing, effectively transferring the precise digital control to the high-frequency domain without requiring the repetition rate to be commensurate with the carrier frequency.
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
Enables precise phase alignment of pulses at arbitrary times, ensuring consistent phase relationships between carriers, overcoming the limitations of existing methods and facilitating accurate quantum processing operations.
Implementation Method 1
a mixer adapted to generate an up-converted signal from the analog oscillator signal and the analog signal set. The up-converted signal has a frequency of ωLOk±ωNCOk with the phase shift φk.
Data Source
AI summary
Method and waveform generator for generating at least two signals. The signals are generated by separate channels, with each channel having a numerically controlled oscillator and a digital envelope generator, whose outputs are multiplied and fed to a digital-analog converter. The signal from the digital-analog converter is multiplied with the signal from a local oscillator for generating pulses with an up-converted carrier. The phases of the numerically controlled oscillators are changed between pulses in order to adjust the phase of the up-converted carrier. This allows to generate pulses where the up-converted carriers have a defined phase relationship.