426 research outputs found
Lasing in circuit quantum electrodynamics with strong noise
We study a model which can describe a superconducting single electron
transistor (SSET) or a double quantum dot coupled to transmission-line
oscillator. In both cases the degree of freedom is given by a charged particle,
which couples strongly to the electromagnetic environment or phonons. We
consider the case where a lasing condition is established and study the
dependence of the average photon number in the resonator on the spectral
function of the electromagnetic environment. We focus on three important cases:
a strongly coupled environment with a small cut-off frequency, a structured
environment peaked at a specific frequency and 1/f-noise. We find that the
electromagnetic environment can have a substantial impact on the photon
creation. Resonance peaks are in general broadened and additional resonances
can appear
Photon-Number Squeezing in Circuit Quantum Electrodynamics
A superconducting single-electron transistor (SSET) coupled to an anharmonic
oscillator, e.g., a Josephson junction-L-C circuit, can drive the latter to a
nonequilibrium photon number state. By biasing the SSET in a regime where the
current is carried by a combination of inelastic quasiparticle tunneling and
coherent Cooper-pair tunneling (Josephson quasiparticle cycle), cooling of the
oscillator as well as a laser like enhancement of the photon number can be
achieved. Here we show, that the cut-off in the quasiparticle tunneling rate
due to the superconducting gap, in combination with the anharmonicity of the
oscillator, may create strongly squeezed photon number distributions. For low
dissipation in the oscillator nearly pure Fock states can be produced.Comment: 5 pages, 5 figure
Irreversibility on the Level of Single-Electron Tunneling
We present a low-temperature experimental test of the fluctuation theorem for
electron transport through a double quantum dot. The rare entropy-consuming
system trajectories are detected in the form of single charges flowing against
the source-drain bias by using time-resolved charge detection with a quantum
point contact. We find that these trajectories appear with a frequency that
agrees with the theoretical predictions even under strong nonequilibrium
conditions, when the finite bandwidth of the charge detection is taken into
account
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