Abstract
We analyse the full counting statistics (FCS) of photons flowing in and out of a microwave cavity coupled to a voltage-biased Josephson junction. Tunnelling of Cooper pairs generates a coherent flow of photons into the cavity whilst at the same time photons can also leak out incoherently. We use a very general unitary transformation method to demonstrate that there is a simple connection between the FCS of the charges and the photons in the long time limit, revealing that all the cumulants of the coherent and the incoherent processes match in that limit. We also explore some of the interesting features in the counting statistics of the charges and photons which arise from the strongly nonlinear dynamics of the system. These include very narrow distributions associated with the emergence of coherent transport and regimes where counting of either an odd or an even number of photons leaving the cavity can result in strongly non-classical cat states within the cavity.
Highlights
The radiation produced by the flow of charges through mesoscopic conductors [1,2,3,4] can be very different to that produced by a classical current [5,6,7], allowing them to be used to produce sources for non-classical light from the microwave up to the low terahertz regime [8,9,10,11,12,13,14]
For systems consisting of a mesoscopic conductor coupled to a cavity mode, illustrated schematically in figure 1(a), charge flow generates a coherent photon flux entering the mode that is balanced by a leakage of radiation out into the wider electromagnetic environment and the mode itself can be thought of as a conductor, albeit a photonic one rather than an electrical one
From this perspective it is natural to ask how the counting statistics of the photons flowing in and out of the mode are related to the statistics of the charge current [20,21,22] and how they respond to the nonlinear quantum dynamics of the system
Summary
Electronic and photonic counting statistics as probes of nonequilibrium quantum dynamics Björn Kubala, Joachim Ankerhold and Andrew D Armour. Tunnelling of Cooper pairs generates a coherent flow this work must maintain attribution to the of photons into the cavity whilst at the same time photons can leak out incoherently. We explore some of the interesting features in the counting statistics of the charges and photons which arise from the strongly nonlinear dynamics of the system. These include very narrow distributions associated with the emergence of coherent transport and regimes where counting of either an odd or an even number of photons leaving the cavity can result in strongly non-classical cat states within the cavity
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