Optical Fiber Qubit Links With Impedance Matching at Cryogenic Interfaces
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Solution Overview
Problem
The challenges of scaling up quantum computers include heat load and space requirements for microwave signal delivery, impedance mismatch, quasiparticle generation, and shot noise in existing coaxial RF cable systems, as well as the inefficiency of optical signal detection in cryogenic environments.
Innovation Solution
A system using optical fibers for signal transfer between a cryogenic system and an external environment, incorporating microwave impedance matching resonators and electro-optic converters, reduces heat dissipation and noise by employing multiplexing and demultiplexing techniques, and uses transducers to convert optical signals to microwave signals within the cryogenic system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If coaxial RF cables with attenuators are used for microwave signal delivery, then signal delivery is achieved, but heat load and space requirements increase
Solution Approach 1:
The patent replaces the mechanical coaxial RF cable system with an optical fiber-based system. Optical fibers transmit microwave signals as optical carriers into the cryogenic system, eliminating the need for physical RF cables that conduct heat. This substitution reduces heat load on the cryogenic system while maintaining signal delivery capability through optical-to-microwave conversion at the cryogenic interface
Solution Approach 2:
The patent introduces optical fibers as an intermediary medium between the external microwave signal source and the cryogenic quantum processor. The optical fiber acts as a mediator that carries signal information without conducting thermal energy, and microwave-to-optical transducers serve as intermediary conversion devices at the cryogenic interface, enabling signal transfer while isolating thermal pathways
2Productivity
If the number of electrical cables is increased to support large numbers of qubits, then signal delivery capacity increases, but space requirements and heat load increase
Solution Approach 1:
The patent merges multiple microwave signal channels onto a single optical fiber using wavelength-division multiplexing. Different microwave signals for multiple qubits are modulated onto optical carriers at different wavelengths, allowing simultaneous transmission of multiple control and readout signals through one fiber, thereby reducing the number of physical connections required at the crowded baseplate interface
Solution Approach 2:
The patent transitions from spatial multiplexing (multiple separate cables) to spectral multiplexing (multiple wavelengths on one fiber). By encoding multiple signals in the frequency domain rather than requiring separate physical pathways, the system can support large numbers of qubits without proportionally increasing the number of cables entering the cryostat, thus reducing baseplate area requirements
3Reliability
If coaxial RF cables are used for signal retrieval, then microwave signals can be retrieved, but impedance mismatch and shot noise occur
Solution Approach 1:
The patent replaces the coaxial cable retrieval system with an optical fiber-based retrieval system. Microwave signals from the quantum processor are converted to optical signals at the cryogenic interface and transmitted through optical fibers to external detectors. This substitution eliminates impedance mismatch issues inherent in RF cable connections and reduces shot noise by using optical detection methods with higher sensitivity and lower noise floors
Solution Approach 2:
The patent introduces optical transducers and optical fibers as intermediaries in the signal retrieval path. The microwave-to-optical transducer converts weak microwave signals from qubits into optical signals that can be transmitted through the fiber with minimal loss and noise. The optical fiber acts as a clean transmission medium that does not introduce the impedance-related distortions and shot noise characteristic of electrical cable systems
4Loss of energy
If optical fibers are used for signal transfer, then heat dissipation is reduced, but optical signal detection in cryogenic environments is inefficient
Solution Approach 1:
The patent segments the detection function from the cryogenic environment. Instead of placing detectors inside the cold stage where optical detection is inefficient, the system uses microwave-to-optical transducers at the cryogenic interface to convert signals to optical form, transmits them through the optical fiber to room temperature, and performs detection externally. This segmentation allows each component to operate in its optimal environment
Solution Approach 2:
The patent uses microwave-to-optical transducers as intermediaries that bridge the cryogenic and room-temperature environments. These transducers convert microwave signals from the quantum processor into optical signals that can be efficiently transmitted through optical fibers and detected by standard room-temperature photodetectors, thereby enabling efficient detection without requiring specialized cryogenic optical detectors
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 approach enables efficient, low-noise, and low-power signal delivery and retrieval, allowing for scalable quantum computing by minimizing heat dissipation and impedance mismatch while maintaining high fidelity qubit control.
Implementation Method 1
at least one optical source (e.g., a laser) for generating optical input signals
Implementation Method 2
a plurality of first transducers for converting the modulated optical signals to microwave input signals and a plurality of second transducers for converting the microwave output signals to optical output signals
Implementation Method 3
A first microwave impedance matching resonator is connected to the plurality of first transducers and a second microwave impedance matching resonator is connected to the plurality of second transducers
Implementation Method 4
A system using optical fibers for signal transfer between a cryogenic system and an external environment
Data Source
AI summary
A system and method for transfer of signals between an inside of a cryogenic system and an external environment including at least one optical source (e.g., a laser) for generating optical input signals and at least one fibre for transferring modulated optical signals to the inside of the cryogenic system and receiving optical output signals from the inside of the cryogenic system. A plurality of detectors, located in the external environment, is used for detecting the optical output signals and are connected to the fibre. A plurality of first transducers converts the modulated optical signals to microwave input signals and a plurality of second transducers converts the microwave input signals to optical output signals. A first microwave impedance matching resonator is connected to the plurality of first transducers and a second microwave impedance matching resonator is connected to the plurality of second transducers.