Qubit-Resonator Dispersive Shift Measurement via AC Stark Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring the dispersive shift of a resonator in superconducting qubit systems are inaccurate and unreliable due to confounding factors such as transfer functions of microwave elements, and require additional system parameters to be measured.
Innovation Solution
A method involving generating resonator response data by preparing a qubit in computational states, applying drive pulses to the resonator and qubit, and measuring the qubit state to determine the dispersive shift, which is self-calibrating and insensitive to complex transfer functions of microwave elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to measure dispersive shift, then measurement can be performed, but measurement precision deteriorates due to confounding factors such as transfer functions of microwave elements
Solution Approach 1:
The patent uses the qubit as an intermediary probe to measure the resonator's dispersive shift. Instead of directly measuring the resonator (which is affected by transfer functions), the qubit interacts with the resonator and its state changes reflect the dispersive shift. This intermediary approach isolates the measurement from the harmful transfer function effects.
Solution Approach 2:
The qubit serves as both the system under study and the measurement tool. By preparing the qubit in different states and measuring its response to resonator drive pulses, the system uses itself to characterize the resonator's dispersive shift, eliminating the need for external calibration references that would be subject to transfer function interference.
2Measurement precision
If existing methods are used to measure dispersive shift, then measurement can be performed, but device complexity increases due to requirement of additional system parameters
Solution Approach 1:
The patent extracts only the necessary measurement information (dispersive shift) through qubit state measurements, eliminating the need to measure and account for additional system parameters such as transfer functions, cable characteristics, and amplifier responses. The qubit measurement directly yields the dispersive shift without requiring these extraneous parameters.
Solution Approach 2:
The qubit serves multiple functions: it acts as a probe for measuring dispersive shift, as a reference for frequency calibration, and as a means to determine linewidth. This multi-functionality eliminates the need for separate measurement systems and parameters, reducing overall device complexity.
3Reliability
If existing methods are used to measure dispersive shift, then measurement can be performed, but reliability deteriorates due to sensitivity to complex transfer functions
Solution Approach 1:
The qubit acts as a mediator that is insensitive to transfer function variations. By coupling the qubit to the resonator and measuring qubit state changes rather than direct resonator response, the measurement becomes reliable and reproducible across different experimental setups and conditions, as the qubit-probe method inherently compensates for transfer function variations.
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 method allows for accurate and reproducible determination of the dispersive shift and linewidth of a resonator, enabling improved control and readout of qubits, and providing better design feedback for quantum circuitry.
Implementation Method 1
measuring the state of the qubit... applying a first drive pulse with the resonator drive frequency to the resonator... The ac Stark shift of the qubit is equal to twice the product of the resonator photon number and the dispersive shift
Implementation Method 2
measuring the dispersive shift of resonance frequency in a superconducting qubit system... processing the generated resonator response data to determine the dispersive shift of the resonator
Data Source
AI summary
Methods, systems, and apparatus for measuring the dispersive shift or linewidth of a resonator coupled to a qubit. In one aspect, a method includes the actions of: generating resonator response data, comprising, for each of two computational states of the qubit: for each of multiple qubit drive frequencies: for each of multiple resonator drive frequencies: preparing the qubit in the computational state; applying a first drive pulse with the resonator drive frequency to the resonator, applying a second drive pulse with the qubit drive frequency to the qubit; measuring the state of the qubit; and processing the generated resonator response data to determine the dispersive shift or linewidth of the resonator.