A review on a 4 K cryogenic refrigeration system for quantum computing

A review on a 4 K cryogenic refrigeration system for quantum computing

This paper reviews the literature that has been published since 1980s related to cryogenic refrigeration systems for quantumcomputing. The reason why such a temperature level of 10-20 mK is necessary for quantum computing is that the superconductingqubit is sensitive to even very small thermal disturbances. The entanglement of the qubits may not be sustained due to thermalfluctuations and mechanical vibrations beyond their thresholds. This phenomenon is referred to as decoherence, and it causes ancomputation error in operation. For the stable operation of the quantum computer, a low-vibration cryogenic refrigeration system isimperative as an enabling technology. Conventional dilution refrigerators (DR), so called ‘wet’ DR, are precooled by liquid helium,but a more convenient and economical precooling method can be achieved by using a mechanical refrigerator instead of liquidcryogen. These ‘dry’ DRs typically equip pulse-tube refrigerators (PTR) for precooling the DRs around 4 K because of its particularadvantage of low vibration characteristic. In this review paper, we have focused on the development status of 4 K PTRs and furtherpotential development issues will be also discussed. A quiet 4 K refrigerator not only serves as an indispensable precooler of DRbut also immediately enhances the characteristics of low noise amplifiers (LNA) or other cryo-electronics of various type quantumcomputers.

This paper reviews the literature that has been published since 1980s related to cryogenic refrigeration systems for quantumcomputing. The reason why such a temperature level of 10-20 mK is necessary for quantum computing is that the superconductingqubit is sensitive to even very small thermal disturbances. The entanglement of the qubits may not be sustained due to thermalfluctuations and mechanical vibrations beyond their thresholds. This phenomenon is referred to as decoherence, and it causes ancomputation error in operation. For the stable operation of the quantum computer, a low-vibration cryogenic refrigeration system isimperative as an enabling technology. Conventional dilution refrigerators (DR), so called ‘wet’ DR, are precooled by liquid helium,but a more convenient and economical precooling method can be achieved by using a mechanical refrigerator instead of liquidcryogen. These ‘dry’ DRs typically equip pulse-tube refrigerators (PTR) for precooling the DRs around 4 K because of its particularadvantage of low vibration characteristic. In this review paper, we have focused on the development status of 4 K PTRs and furtherpotential development issues will be also discussed. A quiet 4 K refrigerator not only serves as an indispensable precooler of DRbut also immediately enhances the characteristics of low noise amplifiers (LNA) or other cryo-electronics of various type quantumcomputers.