Saved in:
| Main Author: | |
|---|---|
| Format: | Recurso digital |
| Language: | |
| Published: |
Zenodo
2025
|
| Online Access: | https://doi.org/10.5281/zenodo.18109751 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866901344931020800 |
|---|---|
| author | Bohac, Leonardo |
| author_facet | Bohac, Leonardo |
| contents | <p>Quantum random access memory (qRAM) remains a persistent bottleneck---not because the lookup specification is unclear, but because implementing a single coherent query can demand deep active control, long-range routing, or unrealistic unit-cost oracle assumptions. We address this tension through a universal, data-independent lookup unitary (U-QRAM) in which the database resides in memory qubits and functions as quantum control. Our first contribution is a hardware-explicit reformulation: U-QRAM equals time evolution under a single time-independent Hamiltonian that is a sum of mutually commuting projector terms---one per memory cell. Because these terms commute, the order of application is irrelevant: they may be executed sequentially or in parallel without changing the target unitary. Our second contribution identifies the most direct path to constant-locality interactions: when addresses are encoded in a unary (one-hot, mode-addressed) register, each Hamiltonian term reduces to 3-local form, replacing the usual (log N)-controlled fan-in barrier with spatial or modal selectivity. We maintain conservative claims: constant latency requires explicit hardware assumptions (global buses, all-to-all connectivity, or native multi-body interactions), and we provide compiled circuit baselines for when such assumptions do not hold.</p> |
| format | Recurso digital |
| id | zenodo_https___doi_org_10_5281_zenodo_18109751 |
| institution | Zenodo |
| language | |
| publishDate | 2025 |
| publisher | Zenodo |
| record_format | zenodo |
| spellingShingle | Direct-Hamiltonian Universal QRAM: Commuting-Projector Lookups and Mode-Addressed Architectures Toward Constant-Latency Queries Bohac, Leonardo <p>Quantum random access memory (qRAM) remains a persistent bottleneck---not because the lookup specification is unclear, but because implementing a single coherent query can demand deep active control, long-range routing, or unrealistic unit-cost oracle assumptions. We address this tension through a universal, data-independent lookup unitary (U-QRAM) in which the database resides in memory qubits and functions as quantum control. Our first contribution is a hardware-explicit reformulation: U-QRAM equals time evolution under a single time-independent Hamiltonian that is a sum of mutually commuting projector terms---one per memory cell. Because these terms commute, the order of application is irrelevant: they may be executed sequentially or in parallel without changing the target unitary. Our second contribution identifies the most direct path to constant-locality interactions: when addresses are encoded in a unary (one-hot, mode-addressed) register, each Hamiltonian term reduces to 3-local form, replacing the usual (log N)-controlled fan-in barrier with spatial or modal selectivity. We maintain conservative claims: constant latency requires explicit hardware assumptions (global buses, all-to-all connectivity, or native multi-body interactions), and we provide compiled circuit baselines for when such assumptions do not hold.</p> |
| title | Direct-Hamiltonian Universal QRAM: Commuting-Projector Lookups and Mode-Addressed Architectures Toward Constant-Latency Queries |
| url | https://doi.org/10.5281/zenodo.18109751 |