Experimental quantum pattern recognition in IBMQ and diamond NVs

TL;DR

This paper explores quantum pattern recognition using swap tests on IBMQ devices and diamond NV centers, demonstrating feasibility for small patterns and proposing a quantum associative memory approach.

Contribution

It introduces a destructive swap test method to improve pattern recognition fidelity on noisy quantum devices and extends the approach to higher-dimensional images.

Findings

Two-qubit swap test detects pattern similarity with good fidelity.

Destructive swap test improves performance for three-qubit states.

Successful implementation of pattern recognition on MRI blood vessel images.

Abstract

One of the most promising applications of quantum computing is the processing of graphical data like images. Here, we investigate the possibility of realizing a quantum pattern recognition protocol based on swap test, and use the IBMQ noisy intermediate-scale quantum (NISQ) devices to verify the idea. We find that with a two-qubit protocol, swap test can efficiently detect the similarity between two patterns with good fidelity, though for three or more qubits the noise in the real devices becomes detrimental. To mitigate this noise effect, we resort to destructive swap test, which shows an improved performance for three-qubit states. Due to limited cloud access to larger IBMQ processors, we take a segment-wise approach to apply the destructive swap test on higher dimensional images. In this case, we define an average overlap measure which shows faithfulness to distinguish between two very different or very similar patterns when simulated on real IBMQ processors. As test images, we use binary images with simple patterns, greyscale MNIST numbers and MNIST fashion images, as well as binary images of human blood vessel obtained from magnetic resonance imaging (MRI). We also present an experimental set up for applying destructive swap test using the nitrogen vacancy centre (NVs) in diamond. Our experimental data show high fidelity for single qubit states. Lastly, we propose a protocol inspired from quantum associative memory, which works in an analogous way to supervised learning for performing quantum pattern recognition using destructive swap test.