<scp>PointerChain</scp> : A Quantum Enabled Dual‐Layer Blockchain <scp>PHR</scp> Sharding Model

ABSTRACT Blockchain sharding is a viable technique for scaling and securing patient health record management through tamper‐proof transactions. The biased randomness in leader election, repeated consensus mechanism, and ledger replication across shards leads to higher cross‐shard communication, which degrades the overall system performance and results in unpredictable node behavior within the shards. The existing sharding approaches exploit state sharding with classical Pseudo Random Node Generator and cryptographic techniques to efficiently allocate nodes to shards and secure access to shards. In this paper, a quantum‐enabled Dual‐Level Blockchain Sharding Model (Q‐PHR) has been proposed to secure Patient Health Records in a sharded network. Firstly, the Quantum Random Node Generator (QRNG) based Shard Formation mechanism allocates nodes to respective shards by generating truly random numbers. Secondly, all the metadata is stored in a pointer chain to reduce cross‐shard communication. Finally, quantum key distribution (QKD) based access control mechanism enables secure communication between medical practitioners and pointer shard. The proposed quantum sharding model is simulated in IBM Quantum Composer utilizing IBM Qiskit, IBM Quantum Provider, Sampler primitives, and the experimental results show that the proposed model achieves enhanced randomness with no duplicates, improved system performance, achieving 71.4% of reduced confirmation latency and 82.1% of increased throughput compared to existing sharding approaches.