Signal Amplification Induced by Multiple Photon Interference in Waveguide QED Systems

Kuan-Ting Lin^1*, Yu-Chen Lin¹, Ting Hsu^1,3, Io-Chun Hoi⁴, Guin-Dar Lin^1,2,3

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Centre for Quantum Science and Engineering, National Taiwan University, Taipei, Taiwan
³Trapped-Ion Quantum Computing Laboratory, Hon Hai Research Institute, Taipei, Taiwan
⁴Department of Physics, City University of Hong Kong, Hong Kong, China

* Presenter:Kuan-Ting Lin, email:alex968.tw@gmail.com

One of the most important ingredients for precision measurement is to amplify the measurement signal as well as increasing its signal-to-noise ratio. However, the high gain amplifier comprising of a single atom interacting to a three dimensional (3D) free space is hard to be achieved due to the spatial modes mismatching, leading to the weak coupling between this atom and the continuum modes of the electromagnetic waves. This weak coupling problem can be solved by confining the radiation fields into a one dimensional (1D) space, whereby the coupling strength can be enhanced. In this study, we theoretically investigate the signal amplification of a quantum amplifier implemented by a single superconducting atom driven by a strong coherent field through the continuum modes of a semi-infinite waveguide. In our setup, the atom can be excited from the ground state to a particular excited state by absorbing multiple photons. We study the underlying mechanism of the gain by analyzing the multiple photon interference originating from the several dressed states. The influence of dephasing on the gain of the amplifier is also included and has been studied. Furthermore, our method also paves a way to realize a multi-atom amplifier, where the resonant dipole-dipole interaction must be taken into account.

Keywords: waveguide QED systems, amplification, multiple photon interference