Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 58: Transport: Poster Session
TT 58.1: Poster
Mittwoch, 9. März 2016, 15:00–18:30, Poster D
Second-order coherence of microwave photons emitted by a quantum point contact — •Daniel Otten and Fabian Hassler — JARA-Institute for Quantum Information, RWTH Aachen University, D-52056 Aachen, Germany
Shot-noise of electrons that are transmitted with probability T through a quantum point contact (biased at a voltage V0) leads to a fluctuating current that in turn emits radiation in the microwave regime. By calculating the Fano factor F for the case where only a single channel contributes to the transport, it has been shown that the radiation produced at finite frequency ω0 close to e V0/ℏ and at low temperatures is nonclassical with sub-Poissonian statistics (F<1). It is the fermionic nature of the electrons producing the radiation, which reduces the probability of simultaneous emission of two or more photons. However, the Fano factor, being a time-averaged quantity, offers only limited information about the system. Here, we calculate the second-order coherence g(2)(τ) for this source of radiation. We show that due to the interference of two contributions, two photon processes (leading to bunching) are completely absent at zero temperature for T=50 %. At low temperatures, we find a competition of the contribution due to Gaussian current-current fluctuations (leading to bunching) with the one due to non-Gaussian fluctuations (leading to antibunching). We show that the competition of the two contributions leads to a nonmonotonic behavior of the second-order coherence as a function of time so that there are times for which the second-order coherence remains below 1 at temperatures where the Fano factor is already above 1.