arXiv subjects

Doyoung Chung

Publications and source records attributed to Doyoung Chung.

3 recordsLinked to original sources

arXiv2026

BPBO: Blindness-Preserving Brickwork Optimization by Certified Region Resynthesis

Universal blind quantum computation (UBQC) hides a client's computation by using a computation-independent BFK09 brickwork graph and encoding the computation in measurement angles, which limits the use of graph-changing optimizations. We study blindness-preserving brickwork optimization (BPBO): certified local resynthesis of BFK09-compatible brickwork patterns below the blinding layer. BPBO detects one-, two-, and three-wire regions; for each candidate region it either proves a semantic floor or supplies an executable witness, and it accepts a replacement only after its branch-frame, output-frame, and blinding behavior have been checked. The optimized outputs remain standard brickwork patterns and are evaluated with a logical qubit-recycled UBQC execution stack that runs arbitrary-length patterns using n x 2 active logical qubits. The layer evidence includes a one-wire H-count floor, a two-wire CNOT-cost floor, a three-wire parity-ledger floor, a clean three-cell CCZ witness whose optimality claim is scoped to the CNOT+T phase-gadget family, and an endpoint-target three-cell CCX/Toffoli application witness; the fixed middle-target CCX case is retained as a four-cell fallback. The security statement is a compatibility result: BPBO preserves UBQC blindness at the declared optimized dimensions and remains compatible with inherited verification guarantees under explicit test-round conditions, without introducing a new trap-soundness theorem. On Bell/CX, Grover-2, endpoint-Toffoli, and Grover-3 evaluation cases, BPBO demonstrates certified local reductions; in the largest case, Grover-3, the materialized pattern is reduced from 3 x 725 to 3 x 98 while preserving the expected marked-state statistics up to sampling noise.

quant-ph↗

arXiv2026

Simulation of Two-Qubit Grover Algorithm in MBQC with Universal Blind Quantum Computation

Simulating the Universal Blind Quantum Computation (UBQC) protocol on gate-based platforms requires updating each measurement basis from earlier outcomes within the same execution. Existing Measurement-Based Quantum Computation (MBQC) simulation tools typically handle this feed-forward outside a single executable quantum program, so they do not natively expose the fixed-graph measurement-by-measurement update order studied here. We address this gap by implementing the flow-based Pauli corrections and a simulation-level UBQC angle-update rule as in-circuit dynamic-circuit primitives in Qiskit. Applied to two-qubit Grover's algorithm on a custom $2\times 9$ flow of 18 qubits, the resulting program achieves deterministic success under both plain MBQC and the UBQC layer. Under the depolarizing-noise setting considered here, the angle-blinding layer remains close to plain MBQC, with only a modest additional gap relative to the dominant MBQC-over-circuit overhead. To show that the construction is not tied only to this Grover-specific pattern, we also verify a $G_{2,5}$ brickwork-state fragment with representative universal-gate primitives under the same client/server blinding view. Structural blindness for a full algorithmic brickwork resource remains future work, but within this scope the construction provides a concrete dynamic-circuit route toward fixed-graph, privacy-preserving delegated-quantum-computing simulation at the protocol-update level.

quant-ph↗

arXiv2025

Partial Blind Quantum Computation: A Framework for Selective Circuit Protection

Quantum computing is rapidly advancing toward cloud-based services, raising significant concerns about the privacy and security of computations outsourced to untrusted quantum servers. Universal Blind Quantum Computation (UBQC) protocols enable clients with limited quantum resources to delegate computations while concealing both inputs and circuit details. However, applying UBQC uniformly to an entire quantum circuit incurs additional quantum resources and computational overhead, which can be a significant burden in practical implementations. In many cases, such as Grover's algorithm, only specific subroutines-like oracles-contain sensitive information, while the rest of the circuit does not require the same level of protection. Therefore, selectively applying UBQC to critical components can enhance computational efficiency while maintaining security. In this work, we propose a selective application of UBQC that targets only the critical components of quantum circuits. By integrating techniques from Quantum Homomorphic Encryption (QHE) and UBQC, our approach secures the sensitive subcircuits while allowing the remaining, non-sensitive portions to be executed more efficiently. In our framework, UBQC-protected sections output quantum states that are encrypted via bit-flip and phase-flip operations, and we devise a mechanism based on selective X and Z gate corrections to seamlessly interface these with unprotected sections. We provide a security analysis demonstrating that our selective UBQC approach preserves universality, correctness, and blindness, and we illustrate its practical advantages through an application to Grover's algorithm. This work paves the way for more efficient and practical secure quantum computing on near-term devices.

quant-ph↗