What blockchain tasks can be delegated to a quantum computer to improve performance and what remain behind the classical infrastructure and What will the API and protocols for interaction between GCUL and a quantum computer look like from the point of view of the application and network layers?

To answer the question on what blockchain tasks can be delegated to quantum computers for performance improvement, which tasks should remain classical, and what the application and network layer API/protocol for interaction between GCUL and a quantum computer might look like, I found several relevant insights:

1. Delegatable Blockchain Tasks to Quantum Computers:

• Mining and consensus tasks can benefit from quantum supremacy by replacing classical proof-of-work with proof of quantum work (PoQ), making mining computationally intractable to classical computers and energy-efficient using quantum annealing processors.arxiv
• Quantum algorithms like QAOA can optimize consensus, improving scalability and energy consumption.rapidinnovation
• Quantum-enhanced blockchains enable parallel transaction processing and more complex smart contracts.rapidinnovation
• Secure multi-party computation (SMPC) and quantum key distribution (QKD) can use quantum properties for privacy and key exchange security improvements.rapidinnovation
• Private delegated quantum computing allows cloud quantum computation with data and operation privacy, which can partially hide computations from classical layers.arxiv

2. Blockchain Tasks Remaining Classical:

• Classical infrastructure handles transaction dissemination, network communication, classical data storage, and maintaining classical validation nodes for robustness and compatibility.uniblock+1
• Protocol orchestration, network consensus messaging, and user-level smart contract interfaces are expected to remain mainly classical while offloading computationally expensive sub-tasks to a quantum back-end.uniblock

3. API and Protocols for GCUL–Quantum Computer Interaction:

• The quantum computing unit will expose delegated computation APIs supporting quantum circuit submission, blind quantum computation protocols (to preserve privacy), and quantum key exchange protocols.arxiv
• Communication involves encrypted quantum states and classical control messages, where the classical layer sends encrypted inputs and instructions, and the quantum unit returns measurement results or decrypted outputs.arxiv
• From the application layer view, the API abstracts quantum computations as services—for example, quantum-enhanced consensus or smart contract execution.
• At the network layer, hybrid protocols combining classical transport with quantum communication or quantum-safe encryption will govern message exchange to and from quantum processing units, enabling secure interoperability between classical GCUL infrastructure and quantum computers.arxiv+1

In summary, quantum computers in a blockchain hybrid architecture like GCUL would mainly handle computationally intensive quantum workloads such as mining, consensus optimization, advanced smart contract processing, and cryptographic primitives. Classical infrastructure would maintain network communication, ledger storage, and interface layers. Interaction APIs would support secure, privacy-preserving quantum delegation protocols integrating classical control and result retrieval, implemented over hybrid quantum-classical network stacks.