Coplanar Antenna Design for Microwave Entangled Signals Propagating in Open Air

Abstract

Open-air microwave quantum communication and metrology protocols must be able to transfer quantum resources from a cryostat, where they are created, to an environment dominated by thermal noise. Indeed, the states carrying such quantum resources are generated in a cryostat characterized by a temperature $T_{\text{in}}\simeq 50$~mK and an intrinsic impedance $Z_{\text{in}}=50\Omega$. Then, an antenna-like device is required to transfer them with minimal losses into open air, characterized by an intrinsic impedance of $Z_{\text{out}}=377\Omega$ and a temperature $T_{\text{out}}\simeq 300$~K. This device accomplishes a smooth impedance matching between the cryostat and the open air. Here, we study the transmission of two-mode squeezed thermal states, developing a technique to design the optimal shape of a coplanar antenna to preserve the entanglement. Based on a numerical optimization procedure, we find the optimal shape of the impedance, and we propose a functional ansatz to qualitatively describe this shape. Additionally, this study reveals that the reflectivity of the antenna is very sensitive to this shape, so that small changes dramatically affect the outcoming entanglement, which could have been a limitation in previous experiments employing commercial antennae. This work is relevant in the fields of microwave quantum sensing and quantum metrology with special application to the development of the quantum radar, as well as any open-air microwave quantum communication protocol.

References in corpus (26)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Charge insensitive qubit design derived from the Cooper pair box
• Entanglement by a beam splitter: nonclassicality as a prerequisite for entanglement
• Coplanar Waveguide Resonators for Circuit Quantum Electrodynamics
• Photon State Tomography for Two-Mode Correlated Itinerant Microwave Fields
• Towards a Distributed Quantum Computing Ecosystem
• Gaussian measures of entanglement versus negativities: the ordering of two-mode Gaussian states
• Microwave quantum illumination using a digital receiver
• Path Entanglement of Continuous-Variable Quantum Microwaves
• Quantum non-demolition detection of an itinerant microwave photon
• Quantum-Enhanced Noise Radar
• Entanglement and purity of two-mode Gaussian states in noisy channels
• Receiver Operating Characteristics for a Prototype Quantum Two-Mode Squeezing Radar
• Quantum Estimation Methods for Quantum Illumination
• Secure quantum remote state preparation of squeezed microwave states
• Planck Spectroscopy and the Quantum Noise of Microwave Beam Splitters
• Displacement of propagating squeezed microwave states
• Experimental quantum teleportation of propagating microwaves
• Quantum illumination reveals phase-shift inducing cloaking
• Flux-driven Josephson parametric amplifiers: Hysteretic flux response and nondegenerate gain measurements
• Finite-time quantum entanglement in propagating squeezed microwaves
• Number-resolved photocounter for propagating microwave mode
• Quantum teleportation of propagating quantum microwaves
• Detecting itinerant single microwave photons
• Inductances and attenuation constant for a thin-film superconducting coplanar waveguide resonator
• Challenges in Open-air Microwave Quantum Communication and Sensing

Cited by in corpus (5)

• Quantum-enhanced pattern recognition
• Perspectives of microwave quantum key distribution in open-air
• Open-Air Microwave Entanglement Distribution for Quantum Teleportation
• Bi-frequency illumination: a quantum-enhanced protocol
• Analytical performance evaluation of quantum radar architectures: From single-photon to entangled-noise radars