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arXiv:2607.27181

Reconfigurable Optical Platform for One-way Quantum Communication Complexity

Francesco Mazzoncini, Hugo Defienne, Romain Alléaume, Sylvain Gigan

quant-phSubmitted Jul 29, 2026• Announced Jul 30, 2026• 0 citations
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Abstract

Demonstrating a practical quantum advantage remains a central goal in quantum information science. While quantum computational supremacy is still technologically demanding, communication complexity offers a promising route to showcase quantum advantage with current photonic platforms. Here we introduce a reconfigurable optical platform for one-way quantum communication complexity based on multimode fibers and wavefront shaping. We experimentally validate it by implementing a genuine one-way quantum communication complexity problem for which an exponential quantum--classical communication separation is known. Complementary numerical simulations show that the same reconfigurable decoding architecture can support more general one-way communication tasks with comparable performance, while also offering a route to higher-dimensional implementations without increasing hardware complexity. Together, these results establish multimode-fiber wavefront shaping as a versatile hardware platform for one-way quantum communication complexity and provide a concrete roadmap toward more demanding protocols, where stronger quantum--classical separations could enable practical demonstrations of quantum advantage.

Comments
25 pages, 9 figures, 3 tables; includes Supplementary Material

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Demonstrating a practical quantum advantage remains a central goal in quantum information science. While quantum computational supremacy is still technologically demanding, communication complexity offers a promising route to showcase quantum advantage with current photonic platforms. Here we introduce a reconfigurable optical platform for one-way quantum communication complexity based on multimode fibers and wavefront shaping. We experimentally validate it by implementing a genuine one-way quantum communication complexity problem for which an exponential quantum--classical communication separation is known. Complementary numerical simulations show that the same reconfigurable decoding architecture can support more general one-way communication tasks with comparable performance, while also offering a route to higher-dimensional implementations without increasing hardware complexity. Together, these results establish multimode-fiber wavefront shaping as a versatile hardware platform for one-way quantum communication complexity and provide a concrete roadmap toward more demanding protocols, where stronger quantum--classical separations could enable practical demonstrations of quantum advantage.
The ability to implement reconfigurable linear optical circuits is a fundamental building block for the implementation of scalable quantum technologies. Here, we implement such circuits in a multimode fiber by harnessing its complex mixing using wavefront shaping techniques. We program linear transformations involving spatial and polarization modes of the fiber and experimentally demonstrate their accuracy and robustness using two-photon quantum states. In particular, we illustrate the reconfigurability of our platform by emulating a tunable coherent absorption experiment, where output probabilities of single- and two-photon survivals can be controlled. By demonstrating complex, reprogrammable, reliable, linear transformations, with the potential to scale, our results highlight the potential of complex media driven by wavefront shaping for quantum information processing.
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Demonstrating a quantum advantage with currently available experimental systems is of utmost importance in quantum information science. While this remains elusive for quantum computation, the field of communication complexity offers the possibility to already explore and showcase this advantage for useful tasks. Here, we define such a task, the Sampling Matching problem, which is inspired by the Hidden Matching problem and features an exponential gap between quantum and classical protocols in the one-way communication model. Our problem allows by its conception a photonic implementation based on encoding in the phase of coherent states of light, the use of a fixed size linear optic circuit, and single-photon detection. This enables us to demonstrate in a proof-of-principle experiment an advantage in the transmitted information resource over the best known classical protocol, something impossible to reach for the original Hidden Matching problem. Our demonstration has implications in quantum verification and cryptographic settings.
We introduce a general mapping for encoding quantum communication protocols involving pure states of multiple qubits, unitary transformations, and projective measurements into another set of protocols that employ coherent states of light in a superposition of optical modes, linear optics transformations and measurements with single-photon threshold detectors. This provides a general framework for transforming a wide class of protocols in quantum communication into a form in which they can be implemented with current technology. In particular, we apply the mapping to quantum communication complexity, providing general conditions under which quantum protocols can be implemented with coherent states and linear optics while retaining exponential separations in communication complexity compared to the classical case. Finally, we make use of our results to construct a protocol for the Hidden Matching problem that retains the known exponential gap between quantum and classical one-way communication complexity.
Quantum communication aims to provide absolutely secure transmission of secret information. Existing methods encode symbols into single photons or coherent light with much less than one photon on average. Here we propose and demonstrate an original method that is fundamentally secure with weak coherent light even when several photons per symbol are used. Our method does not require a change of measurement basis and works with a high-dimensional alphabet in a simple practical setup. Moreover, it sends information in a deterministic way, allowing direct decoding at the receiver end. This feature makes the method suitable for both quantum key distribution (QKD) as well as quantum secure direct communication (QSDC). The key element of our method is the combination of wavefront shaping with a multimode fiber channel. Since it is based on an optical fiber, our method allows to naturally extend secure communication to larger distances.