Photocount statistics of the Josephson parametric amplifier: a question of detection

TL;DR

This paper investigates the photocount statistics of Josephson parametric amplifiers, confirming experimentally that detection processes influence observed statistics and clarifying discrepancies with theoretical predictions.

Contribution

The study experimentally verifies the photocount statistics of Josephson parametric amplifiers and explains how detection processes affect these statistics, resolving previous theoretical discrepancies.

Findings

Experimental confirmation of squeezed vacuum photocount statistics

Detection process influences photocount distribution

Theoretical explanation of discrepancies with prior predictions

Abstract

Parametric amplifiers are known to squeeze the vacuum state of the electromagnetic field, which results in predictable statistics of the photocounts at their output. However, recent theoretical work arXiv:1112.4159 predicts a very different statistical distribution for an amplifier based on a Josephson junction. We test the hypothesis experimentally and recover the expected squeezed vacuum statistics. We explain this discrepancy by showing theoretically how the photocount statistics is dictated by the detection process, from single mode (our experiment) to multimode, fully resolved in frequency (as in arXiv:1112.4159).