Characterisation of a photon pair source using photon-number resolving SNSPDs

Integrated photon-pair sources are primed to play a fundamental role in scaling photonic quantum technologies. Such sources sometimes emit more than one pair of photons due to the probabilistic nature of the emission process. The quality of these sources in terms of their purity and efficiency, is assessed using photon-correlation measurements.

In this paper published in Phys. Rev. Applied 20, 044033, Zhaohui Ma et al. from the Stevens Institute of Technology in NJ USA present the characterisation a highly efficient and integrated source of photon pairs using IDQ’s unique Photon-Number-Resolving detectors. The direct access to photon number statistics allowed the team to verify the single-mode (thermal) nature of their source using a single PNR detector, a feature that is fundamental to later realise entanglement swapping using such sources.

One very interesting aspect is that the authors were measuring pulses of 300-picosecond duration. This duration of a few hundreds of ps is commonly obtained with sources that use a cavity around the downconversion medium, which is the case here. The pulse duration is a factor that can prevent other PNR approaches to work well (see our explanation here). This is especially true with a PNR measurement based on the rising-edge of a single-pixel SNSPD. IDQ’s parallel-SNSPD (P-SNSPD) approach however mitigates this problem, and the value of 300 ps is not hindering the performance of the PNR detection. This also applies well to sources based on quantum dots, which commonly have decay times in the range of a few hundreds of ps.

Moreover, the authors measured photon pairs at a rate of 650 kHz. Thanks to the ultrafast recovery time (few nanoseconds) of IDQ’s latest 28-pixels P-SNSPDs, this could have easily reached several tens of MHz of detection rate while retaining the PNR capability of the detectors. This promises interesting future work for such sources that need to work at very high detection rates. This is ultimately fundamental to allow scaling of photonic quantum technologies.

The same PNR and ultrafast features can apply to any type of sources that can emit more than one photon. In a future series of post we will cover three recent work that used IDQ’s SNSPD to characterise single emitters in silicon to create single-photon sources.

Stay tuned, and we are looking forward to chatting with you regarding your quantum detection needs.

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