Presentation Information
[ED2-03]A novel TES Readout Circuit Combining SQUID and RF-LNAs for Photon-Number-Resolution with sub-ns timing jitter
*Ryutaro Matsumoto1, Yuki Mitsuya2, Hiroyuki Takahashi2 (1. Nuclear Engineering and Management, School of Engineering, UTokyo (Japan), 2. Institute of Engineering Innovation, School of Engineering, UTokyo (Japan))
Keywords:
TES,RF-LNA,SQUID,OQC,photon subtraction
[Purpose]Transition Edge Sensor (TES) is a key technology in Optical Quantum Computing (OQC) forparticularly photon subtraction, i.e., generation of non-classical states of light1,2. One of the majorissues of photon subtraction using TESs is the relatively large timing jitter of TES and its readout(around tens of nanoseconds), compared with the typical wave-packet width of light in OQC(tens ofnanoseconds), which degrades the purity of the generated states3. To address this issue, we propose anovel TES readout scheme that enables sub-nanoseconds timing jitter while maintaining photon-number-resolving (PNR) capability, by combining RF Low-Noise-Amplifiers (RF-LNAs) with aSQUID.[Method]Since the intrinsic resistance rise time of TESs can be sub-nanosecond, the dominant source oftiming jitter is the readout, conventionally based on SQUIDs. We therefore propose a hybrid readoutscheme employing cryogenic RF-LNAs in parallel with SQUIDs. The RF-LNA line, separated fromthe SQUID, preserves the fast rise time of the TES resistance change, while the SQUID ensuresstable photon-number resolution. We employed cryogenic RF-LNAs, and a DC-SQUID fromMagnicon. For optical input, we used 1547 nm and 1310 nm light via SMF28 fiber. To improveimpedance matching between the TES and the RF-LNAs, we fabricated in-house 10 µm square, 12nm thick Ir-TES devices, with a normal resistance of ~20 Ω and intrinsically fast rise times.[Results]We confirmed PNR capability with an average photon number of 2.5 and an energy resolution of0.73 eV (FWHM) at 1310 nm using the SQUID readout. In parallel, the RF-LNA channel achieved asignal rise time of 484 ps (10–90%) when measured with ~200 photons at 1310 nm. For rise-timeestimation, 3000 averaged waveforms were used, since the SNR was not yet sufficient for single-shot analysis at this photon level.[Consideration]We attribute the insufficient energy resolution of the TES to fabrication variation, since betterresolution had been previously achieved with the same design. Regarding the limited SNR of theRF-LNA signal, additional noise sources beyond TES Johnson noise and the intrinsic amplifier noiseare assumed to contribute.
[Conclusion]In this work, we demonstrated, for the first time, a hybrid TES readout achieving sub-nanosecondresponse (484 ps rise time) by employing RF-LNAs in parallel with SQUIDs. This approach enablessimultaneous PNR and sub-nanosecond timing, offering a new path toward stabilizing the generationof non-classical states in optical quantum computing.Future work will aim to employ TES devices with energy resolution below 0.37 eV to increase PNRfidelity at 1547 nm to 99%. In addition, improvements to the electrical system—includingsuppression of reflections and interference, and multi-stage RF-LNA configurations with enhancedperformance—will be pursued. The ultimate goal is to secure sufficient gain without ensembleaveraging and to realize PNR solely from the RF-LNA output.
[Conclusion]In this work, we demonstrated, for the first time, a hybrid TES readout achieving sub-nanosecondresponse (484 ps rise time) by employing RF-LNAs in parallel with SQUIDs. This approach enablessimultaneous PNR and sub-nanosecond timing, offering a new path toward stabilizing the generationof non-classical states in optical quantum computing.Future work will aim to employ TES devices with energy resolution below 0.37 eV to increase PNRfidelity at 1547 nm to 99%. In addition, improvements to the electrical system—includingsuppression of reflections and interference, and multi-stage RF-LNA configurations with enhancedperformance—will be pursued. The ultimate goal is to secure sufficient gain without ensembleaveraging and to realize PNR solely from the RF-LNA output.