Qubit Readout System with Low-Loss Infrared Filter
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Solution Overview
Problem
Current measurement techniques for sensitive quantum systems in the microwave domain, such as superconducting qubits, face challenges in achieving high fidelity and high efficiency due to noise interference from microwave and infrared radiation, which degrades the signal-to-noise ratio and coherence times of the qubits.
Innovation Solution
A qubit readout system incorporating a lossless superconducting circulator, quantum limited directional amplifier, microwave bandpass filter, and low-loss infrared filter with a distributed Bragg reflector is configured to amplify microwave signals while blocking unwanted infrared radiation, ensuring minimal signal attenuation and noise protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement techniques are used for qubit readout, then the system is simpler, but noise from microwave and infrared radiation degrades signal-to-noise ratio and measurement fidelity
Solution Approach 1:
The measurement chain is segmented into multiple functional components: circulator, quantum limited amplifier, bandpass filter, and infrared filter. Each segment addresses specific noise sources or signal processing needs, allowing systematic improvement of measurement fidelity without overwhelming complexity
Solution Approach 2:
A circulator is introduced as an intermediary component between the qubit system and the measurement chain. It directs signals in specific directions and provides isolation, protecting the qubit system from harmful noise while enabling high-fidelity readout
2Measurement precision
If amplification is applied to enhance the microwave readout signal, then signal-to-noise ratio improves, but signal attenuation and loss increase
Solution Approach 1:
A quantum limited amplifier with adjustable gain parameter is employed. The gain can be optimized to achieve the minimum possible noise addition while providing sufficient signal amplification, balancing signal-to-noise ratio improvement with signal attenuation constraints
3Object-affected harmful factors
If filtering components are added to block infrared radiation, then noise protection improves, but signal attenuation increases
Solution Approach 1:
A composite filtering structure is used that combines multiple filtering mechanisms in sequence (bandpass filter followed by infrared filter). This composite approach achieves superior noise rejection while maintaining lower overall signal attenuation compared to single-stage filtering
4Measurement precision
If a full measurement chain with multiple components is implemented, then measurement fidelity improves, but device complexity increases
Solution Approach 1:
The circulator serves multiple functions simultaneously: it directs signal flow, provides isolation between components, and protects the qubit system from noise. This multi-functionality reduces the need for additional dedicated components, managing system complexity
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 configuration enables high fidelity and high efficiency quantum measurements by protecting qubits from noise, maintaining a low signal attenuation of less than 2 dB for microwave signals while effectively blocking infrared radiation, thus improving coherence times and measurement sensitivity.
Implementation Method 1
A low-loss infrared filter has a distributed Bragg reflector integrated into a transmission line, and the low-loss filter is configured to block infrared electromagnetic radiation while passing the microwave readout signal
Implementation Method 2
A quantum limited directional amplifier in which amplification takes place in one direction, and the quantum limited directional amplifier is configured to amplify the microwave readout signal
Implementation Method 3
A lossless superconducting circulator is configured to receive the microwave readout signal from the cavity-qubit system and transmit the microwave readout signal according to a rotation
Data Source
AI summary
A technique relates to a qubit readout system. A cavity-qubit system has a qubit and a readout resonator and outputs a readout signal. A lossless superconducting circulator is configured to receive the microwave readout signal from the cavity-qubit system and transmit the microwave readout signal according to a rotation. A quantum limited directional amplifier amplifies the readout signal. A directional coupler is connected to and biases the amplifier to set a working point. A microwave bandpass filter transmits in a microwave frequency band by passing the readout signal while blocking electromagnetic radiation outside of the microwave frequency band. A low-loss infrared filter has a distributed Bragg reflector integrated into a transmission line. The low-loss filter is configured to block infrared electromagnetic radiation while passing the microwave readout signal. The low-loss infrared filter is connected to the microwave bandpass filter to receive input of the microwave readout signal.