Optical transmission line
Optical transmission lines with glass optical fiber address the thermal challenge of microwave signal transfer between different temperatures, enhancing quantum computer capabilities by reducing heat inflow and increasing signal lines.
Patent Information
- Application Number
- JP2024064281
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-10-14
AI Technical Summary
Sending microwave signals between different temperature regimes, particularly from room temperature to ultra-low temperatures, results in significant thermal energy transfer, making it difficult to maintain the ultra-low temperature required by quantum computer elements.
Using an optical transmission line made of glass instead of conventional metal microwave transmission lines to reduce thermal conductivity and heat flow, employing optical fiber for signal transmission due to its lower thermal conductivity and smaller cross-sectional area.
Reduces heat inflow to less than 1/50 of conventional methods, enabling a significant increase in the number of signal lines, which is crucial for the practical application of quantum computers.
Smart Images
Figure 2025155436000001_ABST
Abstract
Description
[Technical Field]
[0001] Optical transmission line that transmits analog microwaves between temperature differences Summary of the Invention [Problem to be solved by the invention]
[0002] If a large number of microwave signals are sent from room temperature using a microwave transmission line to a quantum computer element that operates at ultra-low temperatures, and the results are then returned to room temperature, a large amount of thermal energy will be sent from room temperature to the ultra-low temperature, making it impossible to maintain the ultra-low temperature. [Means for solving the problem]
[0003] Instead of a microwave transmission line, an optical transmission line designed to enable microwave transmission is used. The optical transmission line is made of glass, which has lower thermal conductivity than metal microwave transmission lines and is thinner than microwave transmission lines, so thermal conduction is doubly reduced. Example 1
[0004] This example is shown in FIG. Microwaves are input from room temperature into electronic equipment that operates at low temperatures, and the signal is processed by the electronic equipment. When transmitting the results back to room temperature, a coaxial cable capable of transmitting microwave electronic signals was used as the transmission path. Coaxial cables usually use copper for both the central and outer conductors. This resulted in a large heat flow from room temperature to low temperature, which required the refrigerator capacity to be increased. Therefore, the coaxial cable was replaced with optical fiber. Optical fiber is made of glass, and because it is thin, it was possible to reduce the heat flow to less than 1 / 50 of that of a coaxial cable. Example 2
[0005] This example is shown in FIG. A 7 GHz analog signal was sent from room temperature to the quantum computer element, which was kept at an ultra-low temperature of 10 mK, via 50 coaxial cables. Thin 0.86 mm diameter coaxial cables were used, and from room temperature to 4 K, a low-thermal-conductivity cable made of CuNi (cupronickel) was used. For temperatures below 4 K, a superconducting cable made of NbTi (niobium titanium) was used. However, because 50 coaxial cables were used for input and 50 for output, one of the largest dilution refrigerators currently available had to be used. Therefore, the coaxial cable was replaced with an optical fiber capable of transmitting analog signals, and the heat inflow was reduced to 1 / 50 of that in the case of a coaxial cable. This makes it possible to cope with the future need to send 1,000-bit signals, which would require 1,000 signal lines. [Industrial Applicability]
[0006] The current bit count of quantum computers is around 100, which is still far from the 1,000-bit or more required for practical use. However, by using optical fiber, the heat inflow is reduced to less than 1 / 50, and the cross-sectional area is reduced to less than 1 / 5. This means that the number of signal lines can be increased by at least 250 times, which will greatly contribute to the practical application of quantum computers in the future. [Brief explanation of the drawings]
[0007] [Figure 1] A device that transmits and receives signals using optical fiber between different temperatures. [Figure 2] A quantum computer that transmits and receives analog signals above 1 GHz using optical fibers between temperatures above 250 K and below 10 K. [Explanation of symbols]
[0008] A Microwave transmission line B Electronic to optical signal converter C Optical transmission line D Optical to electronic signal converter E Electronic device F Power line G Room temperature side H Low temperature side I Quantum computer J 250K or higher K 10K or lower
Claims
1. A device that transmits and receives signals using optical fiber between temperatures above 250K and below 150K.
2. A device that transmits and receives signals using optical fiber between temperature differences of 250K or more and 10K or less.
3. A quantum computer that transmits and receives 1 GHz analog signals using optical fiber between temperatures above 250 K and below 10 K.
4. 4. A quantum computer according to claim 1, 2 or 3, which transmits and receives analog signals of 1 GHz or more using an optical fiber having an electronic-to-optical converter at one end and an optical-to-electronic converter at the other end, between a temperature difference of 250 K or more and 10 K or less.
5. 5. The quantum computer of claim 4, wherein 50 or more optical fibers are used for transmission and 50 or more optical fibers are used for reception.