From Bits to Qubits: Challenges in Classical-Quantum Integration

TL;DR

The paper addresses how to efficiently encode classical data for quantum processing, focusing on quantum image scenarios. It compares three angle-based encoding schemes—Qubit Lattice, Phase Encoding, and FRQI—across runtime, circuit-depth/width, fidelity, and probabilistic readout. The findings show FRQI reduces qubit requirements and can achieve favorable runtimes but incurs deeper circuits and noise, whereas Qubit Lattice and Phase Encoding deliver higher fidelity under hardware constraints. The work informs design choices for hybrid quantum-classical pipelines and provides benchmarking context for the practical impact of encoding decisions on near-term quantum devices.

Abstract

While quantum computing holds immense potential for tackling previously intractable problems, its current practicality remains limited. A critical aspect of realizing quantum utility is the ability to efficiently interface with data from the classical world. This research focuses on the crucial phase of quantum encoding, which enables the transformation of classical information into quantum states for processing within quantum systems. We focus on three prominent encoding models: Phase Encoding, Qubit Lattice, and Flexible Representation of Quantum Images (FRQI) for cost and efficiency analysis. The aim of quantifying their different characteristics is to analyze their impact on quantum processing workflows. This comparative analysis offers valuable insights into their limitations and potential to accelerate the development of practical quantum computing solutions.

Figures (9)

• Figure 1: The Bloch sphere is a geometric representation of a single qubit's quantum state. Any combination of $\alpha, \beta$ values in Eq. \ref{['eq:qstate_1']} that conform to Born's Rule (Eq. \ref{['eq:BornsRule']}) map a given quantum state $\ket{\psi}$ to a point on the surface of the sphere. Image source: Wikimedia Commons.
• Figure 2: Visualizing the Qubit Lattice transformation using a single qubit to encode an angle of $\pi/4$ using a Bloch Sphere.
• Figure 3: Visualizing the Phase Encoding technique using a single qubit to encode an angle of $\pi/4$ using a Bloch Sphere.
• Figure 4: Encoding runtime analysis for the whole range of input sizes and all three encoding techniques.
• Figure 5: Understanding the trend of the core properties of a quantum circuit as we scale the input size.