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1. Circuit and lasing mechanism

Single-artificial-atom lasing and its suppression by strong pumping. S. Ashhab 1,2 , J. R. Johansson 1 , A.M. Zagoskin 1,3 , and Franco Nori 1,2 1 Advanced Science Institute, The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan

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1. Circuit and lasing mechanism

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  1. Single-artificial-atom lasing and its suppression by strong pumping S. Ashhab1,2, J. R. Johansson1 , A.M. Zagoskin1,3, and Franco Nori1,2 1Advanced Science Institute, The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan 2Center for Theoretical Physics, CSCS, Department of Physics, University of Michigan, Ann Arbor, Michigan, USA 3Department of Physics, Loughborough University, Loughborough, UK Summary We consider a system composed of a single artificial atom coupled to a cavity mode. The artificial atom is biased such that the most dominant relaxation process in the system takes the atom from its ground state to its excited state, thus ensuring population inversion. Even under this condition, lasing action can be suppressed if the `relaxation' rate, i.e. the pumping rate, is larger than a certain threshold value. Using simple transition-rate arguments, we derive analytic expressions for the lasing suppression condition and the photon-number state of the cavity in both the lasing and suppressed-lasing regimes. 3. Competition between emission and loss rates 1. Circuit and lasing mechanism Emission from atom to cavity Loss from cavity to environment Maximum value For small n In the steady state If the occupation probability has a peak in n, the location of the peak is approximately given by the equation Going from (a) to (d) G is increased. The red circle marks the most probable number of photons in the cavity Figure (c) corresponds to the “threshold” that separates the lasing and suppressed-lasing states. The atom is biased such that it experiences inverted relaxation from the ground to the excited state. 2. Simplified Hamiltonian and dissipative processes Jaynes-Cummings Hamiltonian: Atom Cavity Coupling Thermal regime Effective temperature can be defined: Master equation: Lasing regime • = cavity decay rate • G = atom excitation rate Supported in part by the NSA, LPS, ARO, NSF and JSPS. arXiv:0803.1209 Corresponding author: Sahel Ashhab, ashhab@riken.jp

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