Abstract
We demonstrate quantum detector tomography of a commercial 2×2 array of superconducting nanowire single photon detectors. We show that detector-specific figures of merit including efficiency, dark-count and cross-talk probabilities can be directly extracted, without recourse to the underlying detector physics. These figures of merit are directly identified from just four elements of the reconstructed positive operator valued measure (POVM) of the device. We show that the values for efficiency and dark-count probability extracted by detector tomography show excellent agreement with independent measurements of these quantities, and we provide an intuitive operational definition for cross-talk probability. Finally, we show that parameters required for the reconstruction must be carefully chosen to avoid oversmoothing the data.
Highlights
Due to their low noise, high timing resolution and excellent efficiency across a broad wavelength range, superconducting nanowire single photon detectors (SNSPDs) have become increasingly prevalent in low-photon-flux optical sensing [1,2,3,4,5]
On the other hand, ”top-down” techniques such as quantum detector tomography can provide an operational description of the device, including many of the figures of merit such as efficiency, dark-count and cross-talk probabilities, without recourse to an underlying model of the detector’s working principle, geometry or readout scheme
As introduced by Lundeen et al [34], the aim of quantum detector tomography is to reconstruct the set of positive operator valued measure (POVM) elements {πn}
Summary
Due to their low noise, high timing resolution and excellent efficiency across a broad wavelength range, superconducting nanowire single photon detectors (SNSPDs) have become increasingly prevalent in low-photon-flux optical sensing [1,2,3,4,5]. Advances in fabrication yield and read-out techniques [6,7,8,9,10,11,12] have enabled arrays of such detectors to be developed [13,14,15,16,17,18,19,20,21,22,23,24], which have lead to applications in imaging [20, 25, 26] and deep space communication [27] Such devices are ideal for multiplexed photon counting in quantum optics experiments. We address the first of these issues, by presenting a tomographic reconstruction of the response of a 2×2 array of SNSPD pixels Using this technique, we can directly quantify the effects of cross-talk, as well as distinguish this from dark noise and determine the detector efficiency. Whilst the salient physics is present in the 2×2-array, this method can be readily generalised to much larger arrays, where characterising pixel-by-pixel becomes highly challenging (and characterising the interpixel correlations prohibitive) with increasing array size
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