Qubit-Resonator Dispersive Shift Measurement via AC Stark Probing
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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.
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 is poor due to confounding factors such as transfer functions of microwave elements
Solution Approach 1:
The patent extracts and removes the confounding transfer function effects from the measurement process by using a self-calibrating method that measures only the qubit state transitions induced by resonator photons, eliminating the need to account for microwave element transfer functions
Solution Approach 2:
The patent uses the qubit state as an intermediary mediator to indirectly measure the resonator photon number and dispersive shift, avoiding direct measurement of the resonator response that would be affected by transfer functions
2Measurement precision
If existing methods are used to measure dispersive shift, then measurement can be performed, but additional system parameters must be measured increasing device complexity
Solution Approach 1:
The patent implements a self-calibrating measurement method where the system uses its own qubit-resonator interaction to determine the dispersive shift without requiring external calibration or additional parameter measurements, making the measurement process self-sufficient
Solution Approach 2:
The patent makes the qubit serve multiple functions: it acts as both the quantum computational element and the measurement probe for determining resonator photon number and dispersive shift, eliminating the need for separate measurement apparatus
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; applying a second drive pulse with the qubit drive frequency to the qubit
Implementation Method 2
measuring the dispersive shift of resonance frequency in a superconducting qubit system... determining 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.