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arXiv:2508.18077 · IEEE International Conference on Quantum Computing and Engineering (QCE)

Quantum Paths: A Quantum Walk Approach

Claudio Pellitteri, Marcello Caleffi, Angela Sara Cacciapuoti

Published Aug 30, 2025• 1 citation
arXivHTMLPDF

Abstract

The quantum switch, a process enabling a coherent superposition of different orders of quantum channels, has garnered significant attention due to its ability to enable noiseless communications through noisy channels, such as entanglementbreaking channels. However, its practical implementation and scalability remain challenging. In contrast, the spatial superposition of quantum channels is more accessible experimentally and has been shown to enhance channel capacity, although it does not match the performance of the quantum switch. In this work, we present preliminary theoretical results demonstrating that, by applying tools of the quantum random walk framework to the spatial superposition of channels, it is possible to replicate the output of a quantum switch. These findings suggest a promising and more feasible route to emulate the quantum switch, offering both practical advantages and interpretative clarity.

DOI
10.1109/qce65121.2025.00139

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In a Quantum Walk (QW) the "walker" follows all possible paths at once through the principle of quantum superposition, differentiating itself from classical random walks where one random path is taken at a time. This facilitates the searching of problem solution spaces faster than with classical random walks, and holds promise for advances in dynamical quantum simulation, biological process modelling and quantum computation. Here we employ a versatile and scalable resonator configuration to realise quantum walks with bright classical light. We experimentally demonstrate the versatility of our approach by implementing a variety of QWs, all with the same experimental platform, while the use of a resonator allows for an arbitrary number of steps without scaling the number of optics. This paves the way for future QW implementations with spatial modes of light in free-space that are both versatile and scalable.
Abstract Applications of the quantum switch on quantum channels have recently become a topic of intense discussion. In the present work, we show that some useless (for communication) channels may provide useful communication under the action of quantum switch for several information-theoretic tasks: quantum random access codes, quantum steering, etc. We demonstrate that the quantum switch can also be useful in preventing the loss of coherence in a system when only coherence-breaking channels are the available channels for communication. We also show that if a useless quantum channel does not provide useful communication even after using a quantum switch, concatenating the channel with another suitable quantum channel, and subsequently using the switch, one may achieve useful communication. Finally, we discuss how the introduction of noise in the quantum switch can reduce the advantage that the switch provides.