Encoding quantum optical states with digitally modulated classical wireless microwave electric-field is shown for the first time. This paves the way for seamless integration of classical digital wireless links and quantum optical communication links in future.
This paper establishes the theoretical framework to enable the seamless transfer of digital information from the classical microwave domain to the quantum optical domain in wireless-to-optical converters. It introduces a quantum mechanical network model to characterize digital information mapping from microwave to optical domains in seamless wireless-to-optical converters based on antenna-coupled electro-optic modulators. Key design principles are outlined to optimize information mapping strength, supported by analytical and physical reasoning. The model is further extended to demonstrate phase-space encoding of optical coherent states using classical microwave constellations. In addition, the framework addresses the challenge of inter-symbol overlap in the quantum optical phase-space due to quadrature fluctuations and proposes a potential mitigation technique. The foundational framework established in this paper can also enable the encoding of other nonclassical states of light, such as squeezed states, thereby paving the way for integrating classical microwave and quantum optical links in the near future.
This paper develops a theoretical framework for enabling seamless transfer of digital information from classical microwave domain to the quantum optical domain in wireless-to-optical converters. A quantum mechanical network model is introduced to characterize microwave-to-optical digital information mapping in antenna-coupled electro-optic modulator-based converters. Design guidelines are discussed to maximize the information mapping strength. The derived model is then extended to show phase-space encoding of optical coherent-states with classical wireless microwave constellation. Further, the challenge of inter-symbol overlap in the encoded quantum optical phase-space due to quadrature fluctuations is highlighted. The possibility of erroneous phase-space encoding due to quadrature fluctuations is pointed out, followed by a potential mitigation technique. The presented framework also lays the groundwork for encoding other non-classical states of light such as squeezed states, and hence forms the basis for bridging classical microwave and quantum optical links in the near future.
Linking classical microwave electrical circuits to the optical telecommunication band is at the core of modern communication. Future quantum information networks will require coherent microwave-to-optical conversion to link electronic quantum processors and memories via low-loss optical telecommunication networks. Efficient conversion can be achieved with electro-optical modulators operating at the single microwave photon level. In the standard electro-optic modulation scheme this is impossible because both, up- and downconverted, sidebands are necessarily present. Here we demonstrate true single sideband up- or downconversion in a triply resonant whispering gallery mode resonator by explicitly addressing modes with asymmetric free spectral range. Compared to previous experiments, we show a three orders of magnitude improvement of the electro-optical conversion efficiency reaching 0.1% photon number conversion for a 10GHz microwave tone at 0.42mW of optical pump power. The presented scheme is fully compatible with existing superconducting 3D circuit quantum electrodynamics technology and can be used for non-classical state conversion and communication. Our conversion bandwidth is larger than 1MHz and not fundamentally limited.
A critical aspect of next-generation wireless networks is the integration of quantum communications to guard against quantum computing threats to classical networks. Despite successful experimental demonstrations, integrating quantum communications into the classical infrastructure faces substantial challenges, including high costs, compatibility issues, and extra hardware deployment to accommodate both classical and quantum communication equipment. To mitigate these challenges, we explore novel protocols that enable simultaneous classical and quantum communications, relying on a single set of transceivers to jointly modulate and decode classical and quantum information onto the same signal. Additionally, we emphasize extending quantum communication capabilities beyond traditional optical bands into the terahertz, even possibly to millimeter-wave and microwave frequencies, thereby broadening the potential horizon of quantum-secure applications. Finally, we identify open problems that must be addressed to facilitate practical implementation.
This paper establishes the Heisenberg's picture framework for seamless mmWave-to-photonic data transduction. Based on this framework, contactless modulation of continuous-variable (CV) quantum optical states with digitally modulated classical mmWave beams is shown for the first time. Our analysis reveals the direct influence of mmWave phase variation on the Wigner-space evolution of modulated optical coherent and squeezed states. Furthermore, the analysis indicates that classical mmWave phase not only governs the displacement but also modulates the quadrature uncertainty of squeezed states, revealing a novel technique for embedding information onto multiple quantum-optical degrees of freedom. This work builds the theoretical and analytical foundation for wireless conditioning of quantum light without conventional on-chip metallic interconnects and complex electronic control circuitry, thereby opening a key pathway toward seamless bridging of integrated quantum photonics with emerging mmWave or THz communication technology.