Abstract
We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor $F$) for a Josephson-junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e. noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state ($F<1$), as has been established previously [A. D. Armour, et al., Phys. Rev. Lett. 111, 247001 (2013)], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.
Highlights
INTRODUCTIONWhen a Josephson junction (JJ) device is embedded within a superconducting microwave cavity, the energy supplied by a dc voltage bias can be converted into microwave photons.[1,2,3,4,5] The resulting radiation is predicted to display non-classical properties over a wide range of conditions,[6,7,8,9,10,11,12,13,14,15,16] some of which have been demonstrated in experiment.[5] the state of the microwave cavity in such systems is strongly dependent on its quality factor Q: for low Q the photons leak out as fast as they are generated, while for high Q a large nonequilibrium photon population can build up
We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor F ) for a Josephson-junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating bias voltage with finite dc average
Since it is not possible to entirely eliminate bias noise in real devices, it is important to determine its effect on the quantum dynamics and in particular on the predicted amplitude squeezing of the microwave steady states which are expected to be sensitive to various sources of noise
Summary
When a Josephson junction (JJ) device is embedded within a superconducting microwave cavity, the energy supplied by a dc voltage bias can be converted into microwave photons.[1,2,3,4,5] The resulting radiation is predicted to display non-classical properties over a wide range of conditions,[6,7,8,9,10,11,12,13,14,15,16] some of which have been demonstrated in experiment.[5] the state of the microwave cavity in such systems is strongly dependent on its quality factor Q: for low Q the photons leak out as fast as they are generated, while for high Q a large nonequilibrium photon population can build up.
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