The photonic content of a transmission-line pulse

• 成果类型: Article
• 署名作者: Varvelis, Evangelos; Biswas, Debjyoti; DiVincenzo, David P.
• 署名单位: Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Madras; Helmholtz Association; Research Center Julich
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11909
• DOI: 10.1073/pnas.2314846121
• 发表日期: 2024-01-23
• 关键词: quantum; amplification; coherent

摘要

We develop a photonic description of short, one-dimensional electromagnetic pulses, specifically in the language of electrical transmission lines. Current practice in quantum technology, using arbitrary waveform generators, can readily produce very short, fewcycle pulses in a very -low -noise, low -temperature setting. We argue that these systems attain the limit of producing pure coherent quantum states, in which the vacuum has been displaced for a short time, and therefore over a short spatial extent. When the pulse is bipolar, that is, the integrated voltage of the pulse is zero, then the state can be described by the finite displacement of a single mode. Therefore there is a definite mean number of photons, but which have neither a well-defined frequency nor position. Due to the Paley-Wiener theorem, the two -component photon wavefunction of this mode, while somewhat localized, is not strictly bounded in space even if the vacuum displacement that defines it is bounded. When the pulse is unipolar, no photonic description is possible-the photon number can be considered to be divergent. We consider properties that photon counters and quantum non -demolition detectors must have to optimally convert and detect the photons in several example pulses. We develop a conceptual test system for implementing short -pulse quantum key distribution, building on the design of a recently achieved Bell's theorem test in a cryogenic microwave setup.