Superconducting Quantum Processor Cooling With Immersion Helium
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Solution Overview
Problem
Existing quantum circuits face challenges in achieving optimal operating temperatures due to poor thermal conductivity and electromagnetic interference, leading to decoherence and reduced coherence times, which are exacerbated by competing temperature-dependent mechanisms such as quasiparticles, TLS defects, and thermal population, making it difficult to improve performance beyond current 50 mK limits.
Innovation Solution
The method involves immersing the quantum circuit in a cooling fluid, such as liquid 3He, within an enclosure with porous media and a control unit to manage the temperature and thermal coupling, allowing adaptive control of the operating temperature to optimize performance across a broader range, including improved thermalization of TLS and surface spins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If quantum circuits are cooled to low temperatures to reduce decoherence, then coherence time is improved, but temperature-dependent mechanisms such as quasiparticles, TLS defects, and thermal population create competing effects that limit further improvement
Solution Approach 1:
The patent applies different thermal coupling strengths to different parts of the quantum circuit by using variable thermal conductance elements. This allows specific regions with different decoherence mechanisms to be optimally thermalized at different effective temperatures, addressing the local nature of various temperature-dependent harmful effects rather than applying a uniform cooling approach to the entire circuit.
Solution Approach 2:
The patent implements dynamic thermal coupling by making the thermal conductance between the quantum circuit and heat sink adjustable during operation. This allows the system to adaptively respond to changing thermal conditions and decoherence mechanisms, optimizing coherence time by dynamically balancing the competing temperature-dependent effects rather than relying on static cooling.
2Temperature
If thermal coupling is increased to improve thermalization, then operating temperature is reduced, but thermal conductivity limitations and electromagnetic interference prevent effective cooling
Solution Approach 1:
The patent introduces thermal interface materials and thermal conductance elements as intermediaries between the quantum circuit and heat sink. These intermediaries mediate the thermal coupling, enabling effective heat transfer while maintaining electromagnetic isolation and addressing the dual constraints of thermal conductivity requirements and electromagnetic interference prevention.
Solution Approach 2:
The patent employs composite thermal management structures that combine materials with different properties - some components optimized for thermal conductivity and others for electromagnetic shielding. This composite approach allows simultaneous achievement of effective thermalization and electromagnetic interference protection, resolving the contradiction between these two requirements.
3Reliability
If adaptive temperature control is implemented to optimize performance, then coherence and fidelity are improved, but system complexity increases
Solution Approach 1:
The patent implements feedback control by monitoring temperature and performance metrics of the quantum circuit and adjusting thermal coupling accordingly. This feedback mechanism enables automatic optimization of coherence and fidelity without requiring complex manual intervention, as the system self-regulates to maintain optimal operating conditions despite the added control complexity.
Solution Approach 2:
The patent enables the quantum circuit system to self-regulate its thermal conditions through integrated sensors and control elements that automatically adjust thermal coupling based on real-time performance feedback. This self-service approach allows the system to optimize its own coherence and fidelity without external intervention, managing the complexity internally while delivering improved performance.
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 significantly enhances thermalization, increasing coherence times and improving performance metrics like qubit fidelity and gate fidelity by controlling temperature below 100 mK, addressing the limitations of current thermalization methods.
Implementation Method 1
immersing the quantum circuit in a cooling fluid, such as liquid 3He, within an enclosure with porous media and a control unit to manage the temperature and thermal coupling
Implementation Method 2
a volume of porous media made of thermally conductive material disposed in the enclosure and thermally coupled to at least a part of the enclosure walls
Data Source
AI summary
A system for controlling the temperature of a quantum circuit comprises an enclosure comprising enclosure walls made of temperature conductive material; a substrate for holding a quantum circuit; at least one source of cooling fluid; at least one port in the enclosure coupled to at least one source of cooling fluid; a control unit coupled to at least one source of cooling fluid and configured to control or enable the control of supply of cooling fluid to the chamber; wherein the system in use fills the enclosure with cooling fluid so as to cool the quantum circuit. Preferably, at least one source of cooling fluid is a source of 3He, 4He or a mixture of the two. The invention provides a method and system for optimising the operating temperatures of superconducting quantum circuits and processors and the environment they operate in.