Variational Quantum Integrated Sensing and Communication Enables Superdense Coding and Parameter Estimation with Adaptable Classical Machine Learning

The demand for increasingly sophisticated wireless networks drives innovation in how information is transmitted and received, and researchers are now exploring the potential of quantum technologies to meet these challenges. Ivana Nikoloska from Eindhoven University of Technology and Osvaldo Simeone from King’s College London, along with their colleagues, present a new approach to integrated sensing and communication that harnesses the power of quantum entanglement. Their work introduces a protocol which simultaneously enables superdense coding and parameter estimation, offering a flexible balance between communication speed and sensing accuracy. This integrated system represents a significant step towards realising the potential of quantum networks, paving the way for more efficient and powerful communication technologies.

Entanglement Enables Joint Sensing and Communication

This research pioneers a novel integrated sensing and communication (ISAC) protocol, termed QISAC, which harnesses entanglement to simultaneously transmit information and estimate unknown channel parameters. The study establishes a system where a third party generates maximally entangled states of two qudits and distributes them to Alice and Bob, forming the foundation for joint sensing and communication. Alice encodes a message, represented as a pair of integers, onto her qudit using a carefully designed transformation, preparing the state for transmission. This encoding process allows for a controlled trade-off between communication rate and sensing accuracy.

Following message encoding, Alice transmits her qudit through a channel dependent on an unknown parameter to Bob. This channel imbues the transmitted qudit with a dual role as both a carrier of information and a probe of the channel. Upon receiving Alice’s qudit, Bob possesses two qudits, enabling a joint measurement strategy designed to simultaneously decode the message and estimate the channel parameter. The research details the mathematical formulation of these transformations and channel operations, establishing a precise framework for analyzing the performance of the QISAC protocol. The study explores qudit-based transmission strategies, allowing for a tunable communication rate reduction, and provides numerical results illustrating this trade-off between communication and sensing performance. This approach allows for a flexible balance between reliable message transmission and precise channel characterization, demonstrating the versatility of the proposed QISAC protocol.

Entangled Qudits Enable Sensing and Coding

Scientists have developed a novel quantum integrated sensing and communication (QISAC) protocol that simultaneously enables both superdense coding and quantum sensing, representing a significant advancement in next-generation network technologies. The research centers on leveraging entanglement between quantum particles to achieve a flexible trade-off between communication rate and the accuracy of parameter estimation. Experiments utilize qudit systems, quantum units generalizing the qubit, to transmit information and perform sensing tasks. The team prepared maximally entangled two-qudit states and distributed them between a transmitter (Alice) and a receiver (Bob).

Alice encodes classical information using a variant of superdense coding, while Bob employs a variational quantum circuit to optimize the measurement strategy, coupled with neural network-based decoders and estimators for classical post-processing. This hybrid quantum-classical system is trained end-to-end to optimize a weighted sum of communication and sensing performance. The protocol allows for a communication rate reduction to enhance the precision of quantum sensing. Specifically, the research demonstrates the transmission of messages encoded as pairs of integers. The results illustrate the inherent trade-off between maximizing communication rate and achieving higher accuracy in parameter estimation. This work establishes a foundation for future development of integrated quantum networks capable of simultaneously sensing and communicating information with enhanced efficiency and precision.

Simultaneous Quantum Communication and Sensing Protocol

This research presents a novel protocol for integrated quantum communication and sensing, demonstrating how a quantum receiver can be trained to simultaneously decode classical messages and estimate unknown parameters. By leveraging entangled probe states and a hybrid quantum-classical optimization approach, the team successfully adapted the receiver’s measurement strategy to balance these dual tasks. Simulations characterized the trade-off between communication throughput and sensing accuracy, revealing that the developed design operates effectively with both non-zero communication rates and high sensing precision. The work establishes a flexible framework with potential for expansion, as the researchers focused on discrete parameter estimation but acknowledge the possibility of extending the protocol to continuous parameters or multi-parameter sensing scenarios. Further improvements could be achieved through the use of more expressive parameterized circuits, although this would increase circuit complexity. Addressing performance reliability under noisy conditions and model uncertainty represents another key area for future investigatio08