A NISQ-friendly Coined Quantum Walk Algorithm for Chaos-based Cryptographic Applications
Natalie Gibson, Niklas Keckman, Andrea Marchesin, Matti Raasakka, Ilkka Tittonen

TL;DR
This paper introduces a depth-efficient LAQW quantum algorithm suitable for NISQ devices, demonstrating its application in chaos-based cryptography and key generation with reproducible 128-bit keys under simulated noise.
Contribution
The paper proposes a novel LAQW algorithm with significantly reduced circuit depth compared to existing models, enabling practical NISQ implementation for cryptographic purposes.
Findings
LAQW circuit depth scales as O(n^2 + nt), a reduction from O(n^2 t) in CAQW.
Reproducible 128-bit keys generated under simulated quantum noise.
LAQW demonstrates potential in cryptographic applications like key generation and image encryption.
Abstract
We present a novel lackadaisical alternating quantum walk (LAQW) algorithm whose circuit depth scales as for a lattice over time steps. We show that this is a significant depth reduction compared to the existing controlled alternating quantum walk (CAQW) model, which has a circuit depth that scales as (Li et al., 2017, arXiv:1707.07389). This makes the implementation of the LAQW viable for Noisy Intermediate-scale Quantum (NISQ) devices. We then showcase the applicability of the LAQW algorithm by proposing a chaos-based symmetric-key generation scheme. Our approach uses the LAQW as a quantum entropy source from which reproducible random bitstring sequences are generated using the underlying probability distribution and subsequent post-processing methods. We provide a comprehensive evaluation of the LAQW algorithm and demonstrate…
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