Private Quantum Database

TL;DR

This paper introduces a quantum database model that simultaneously guarantees data privacy and user privacy by leveraging quantum superposition and measurement, enabling secure data access without heavy cryptography.

Contribution

It proposes a novel quantum database architecture using QRACs over MUBs that protects both data and user privacy without trusted hardware or cryptography.

Findings

Quantum superposition collapses upon measurement, making unqueried data inaccessible.

The model allows secure retrieval of specific data entries with minimal quantum states.

Compatibility with Noisy Intermediate-Scale Quantum devices is demonstrated.

Abstract

Quantum databases open an exciting new frontier in data management by offering privacy guarantees that classical systems cannot match. Traditional engines tackle user privacy, which hides the records being queried, or data privacy, which prevents a user from learning more than she has queried. We propose a quantum database that protects both by leveraging quantum mechanics: when the user measures her chosen basis, the superposition collapses and the unqueried rows become physically inaccessible. We encode relational tables as a sequence of Quantum Random Access Codes (QRACs) over mutually unbiased bases (MUBs), transmit a bounded number of quantum states, and let a single, destructive measurement reconstruct only the selected tuple. This allows us to preserve data privacy and user privacy at once without trusted hardware or heavyweight cryptography. Moreover, we envision a novel hybrid quantum-classical architecture ready for early deployment, which ensures compatibility with the limitations of today's Noisy Intermediate-Scale Quantum devices.