Sub-Kelvin Cooling with GM-Type 4K Cryocooler + He3 Module
Outlook for Semiconductor Quantum Computers
Background
Semiconductor qubits (such as silicon quantum dots) do not require the ultra-low temperatures (10–20 mK) demanded by superconducting qubits. Instead, designs that can operate at 0.3–1 K are advancing. Traditional dilution refrigerators are large, expensive, and complex, creating barriers for R&D. For the scaling of quantum processors and their industrial deployment, compact, cost-effective cooling solutions that can reach the sub-Kelvin regime are essential.
Technical Configuration
- GM cryocooler (4K-class): Achieves cooling down to 4 K without liquid helium using a compressor + displacer. Representative systems include Cryomech and Bluefors 4K clusters.
- He3 sorption module: Uses activated charcoal sorption pumps for evaporative cooling, achieving ~0.3 K. Commercial examples include Chase Research GL7.
- Cooling power: Tens of µW at 0.3 K, >100 µW at 1 K — sufficient for gate wiring and small-scale circuit testing of semiconductor quantum devices.
- Operation modes: Single-shot operation (12–24 h hold time) or continuous cooling with dual-module switching.
Performance and Limitations
- Base temperature: Typically 0.3 K (down to ~0.25 K under light load).
- Cooling power: Lower than dilution refrigerators (tens of µW @ 20 mK), but adequate for semiconductor quantum dot circuits and small QPU validation.
- Stability: mK-scale fluctuations, requiring active compensation.
- Advantages: Compact (rack/benchtop), lower cost (a fraction of dilution fridges), easy installation, and energy-efficient.
Existing Products and New Trends
- Chase Research GL series: Supports ~0.3 K operation, with proven use in semiconductor quantum circuits.
Significance for Semiconductor Quantum Computers
- Resource savings: Dilution refrigerators demand large infrastructure and high cost, while GM+He3 systems are viable at the lab scale.
- Miniaturization and accessibility: Off-the-shelf 0.3–0.5 K units are entering the market, broadening access to semiconductor qubit development.
- From R&D to production testing: Small modules can start with device evaluation and scale up, making parallel installation with fabrication equipment feasible.
- blueqat’s vision: From the end of 2025, blueqat will progressively adopt this approach, advancing semiconductor quantum computer demonstrations and productization — bridging the gap between R&D and real-world deployment.
Conclusion
GM+He3 cryocoolers, capable of reaching 0.3 K without dilution refrigeration, represent a key enabling technology for taking semiconductor quantum computers from the lab to industry. Compact and resource-efficient sub-Kelvin cooling recalls the historical shift from mainframes to personal computers.
Quantum computer cooling technology itself now stands at a major turning point.