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Single-qubit lasing in the strong-coupling regime

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • Stephan André
  • Pei Qing Jin
  • Valentina Brosco
  • Jared H. Cole
  • Alessandro Romito
  • Alexander Shnirman
  • Gerd Schön
Article number053802
<mark>Journal publication date</mark>6/12/2010
<mark>Journal</mark>Physical Review A - Atomic, Molecular, and Optical Physics
Issue number5
Publication StatusPublished
<mark>Original language</mark>English


Motivated by recent "circuit QED" experiments we study the lasing transition and spectral properties of single-qubit lasers. In the strong coupling, low-temperature regime, quantum fluctuations dominate over thermal noise and strongly influence the linewidth of the laser. When the qubit and the resonator are detuned, amplitude and phase fluctuations of the radiation field are coupled and the phase diffusion model, commonly used to describe conventional lasers, fails. We predict pronounced effects near the lasing transition, with an enhanced linewidth and nonexponential decay of the correlation functions. We cover a wide range of parameters by using two complementary approaches, one based on the Liouville equation in a Fock-state basis, covering arbitrarily strong coupling but limited to low photon numbers, the other based on the coherent-state representation, covering large photon numbers but restricted to weak or intermediate coupling.