Josephson LNA Matching Circuit for Low-Noise Pump-Free Amplification
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Solution Overview
Problem
Voltage-biased Josephson junction amplifiers face challenges in achieving noise levels similar to parametric amplifiers while maintaining simplicity, with existing amplifiers having higher noise levels than parametric amplifiers and complexity in pump generation.
Innovation Solution
An adaptation circuit with specific impedance matching conditions, including Re(Z(fs)) > 0, Re(Z(fi)) > 0, and Re(Z(fp)) > 0, stabilizes the operating point and prevents photon conversion at signal frequency fs, reducing unnecessary noise and ensuring signal amplification without losing the signal to other frequencies, using a non-linear impedance with a superconductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a voltage-biased Josephson junction amplifier is used, then the device complexity is reduced by eliminating the pump generation requirement, but the noise level increases to around 10 photons (20 times the quantum limit)
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the impedance parameters of the matching circuit at specific frequencies. The real part of the impedance is set to positive values at signal frequency (Re(Z(fs)) > 0), idler frequency (Re(Z(fi)) > 0), and pump frequency (Re(Z(fp)) > 0), while the imaginary part is tuned to create resonant conditions. This precise parameter optimization enables the voltage-biased Josephson junction to achieve noise levels close to the quantum limit while maintaining operational simplicity.
2Object-generated harmful factors
If a parametric amplifier with pump generation is used, then the noise level is reduced close to the quantum limit, but the device complexity increases due to pump generation requirements
Solution Approach 1:
The patent extracts and eliminates the pump generation component from the amplifier system. By using a voltage-biased Josephson junction with a carefully designed matching circuit, the amplifier achieves parametric amplification behavior without requiring an external pump signal source. The bias voltage applied to the Josephson junction inherently provides the necessary energy modulation, simplifying the overall device architecture while maintaining low noise performance.
Solution Approach 2:
The voltage-biased Josephson junction serves itself by using the applied bias voltage to generate the necessary conditions for parametric amplification. The junction's nonlinear inductance, combined with the resonant matching circuit, automatically creates the frequency mixing and amplification effects that traditionally required an external pump signal. This self-service mechanism eliminates the need for separate pump generation hardware.
3Productivity
If the impedance matching circuit allows photon conversion at signal frequency, then amplification can occur, but the signal may be lost to other frequencies and noise increases
Solution Approach 1:
The patent applies local quality by creating distinct impedance characteristics at different frequency points. The matching circuit is designed with specific resonant elements that provide positive real impedance and appropriate imaginary impedance at the signal frequency (fs), idler frequency (fi), and pump frequency (fp) independently. This localized impedance optimization ensures that photon conversion occurs efficiently at the desired frequencies while preventing signal energy from being converted to unwanted frequencies, thereby maintaining signal integrity and reducing noise.
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 reduces noise in voltage-biased Josephson junction amplifiers to levels comparable to parametric amplifiers, simplifies the device by eliminating the need for a pump, and maintains high amplification efficiency by optimizing the impedance matching circuit's design.
Implementation Method 1
voltage-biased Josephson junction amplifier
Implementation Method 2
non-linear impedance with a superconductor
Implementation Method 3
adaptation circuit with specific impedance matching conditions, including Re(Z(fs)) > 0, Re(Z(fi)) > 0, and Re(Z(fp)) > 0
Data Source
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AI summary
One aspect of the invention relates to an impedance matching circuit intended to be connected to a non-linear impedance comprising a superconductor, said circuit comprising a first terminal called a first connection port intended to be connected to a first terminal of the nonlinear impedance, a second terminal called the second connection port intended to be connected to a second terminal of the nonlinear impedance, a third terminal called the input/output terminal intended to receive the signal to be amplified and a fourth terminal called supply terminal intended to be connected to a bias source and configured so that a voltage V is applied between the first connection port and the second connection port. The circuit according to the invention comprises a plurality of passive electrical components configured so that the impedance Z(f) between the first connection port (J1) and the second connection port (J2) for a signal of frequency f has a part real Re(Z(f)) such that Re(Z(fs))>0 with fs a first frequency called signal frequency; Re(Z(fi)) > 0 with fi a second frequency called the idler frequency; ReZ0<h4e2fpG.BW with fp a third frequency called the pump frequency; ReZfp+fs<fp+fsfiReZfi; the pump frequency being chosen so that nfp = fs + fi with n an integer belonging to [1, +∞] and the idler frequency being chosen so that fi>kBTh with T the circuit temperature, kB the Boltzmann constant and h is Planck's constant.