Counting near infrared photons with microwave kinetic inductance detectors

Abstract

We demonstrate photon counting at 1550 nm wavelength using microwave kinetic inductance detectors (MKIDs) made from TiN/Ti/TiN trilayer films with superconducting transition temperature Tc ≈ 1.4 K. The detectors have a lumped-element design with a large interdigitated capacitor covered by aluminum and inductive photon absorbers whose volume ranges from 0.4 µm 3 to 20 µm 3 . The energy resolution improves as the absorber volume is reduced. We achieved an energy resolution of 0.22 eV and resolved up to 7 photons per optical pulse, both greatly improved from previously reported results at 1550 nm wavelength using MKIDs. Further improvements are possible by optimizing the optical coupling to maximize photon absorption into the inductive absorber.Photon-number-resolving (PNR) detectors at near infrared wavelengths have important applications in a number of frontier fields, such as quantum secure communications [1], linear optical quantum computing [2] and optical quantum metrology [3]. Compared to more conventional detectors at this wavelength, such as siliconbased detectors [4], superconducting detectors have lower dark-count rate, higher sensitivity, and broadband response. They show great promise in serving as the basic building blocks for efficient PNR devices. For example, by spatial or temporal multiplexing of superconducting nanowire single-photon detectors (SNSPDs) [5][6][7][8], photons can be counted at high speed. But the singleelement nanowire has no intrinsic PNR and energyresolving capabilities. Alternatively, single-element transition edge sensors (TESs) [9] have demonstrated high quantum efficiency and multi-photon discrimination at telecommunication wavelengths [10][11][12]. Recently, counting up to 29 photons and intrinsic energy resolution ≈ 0.11 eV at 1550 nm wavelength have been achieved in Ti/Au TESs [13][14][15].Another type of superconducting detector possessing intrinsic photon-number-resolving and energy-resolving power is the microwave kinetic inductance detector (MKID) [16]. MKIDs are cooper pair breaking detectors based on high-quality factor (high-Q) superconducting resonators [17,18]. The absorption of a photon with energy higher than twice the gap energy (hν > 2∆) can break Cooper pairs into quasiparticles, changing the surface impedance of the resonator and resulting in a lower resonance frequency f r and higher internal dissipation (or lower quality factor Q i ). When applying a short optical pulse to the detector and probing the resonator with a * Electronic mail: qubit@home.swjtu.edu.cn † Electronic mail: weilianfu@gmail.com ‡ Contribution of the U.S. government, not subject to copyright microwave tone near the resonance frequency, one can obtain a pulse response in the complex forward transmission S 21 , as shown in Fig. 1(a). This photon response can be measured using a homodyne detection scheme ( Fig. 1(d)) and the signal can be decomposed into frequency and dissipation responses ( Fig. 1(a),(b)) for pulse analysis. Compared to TESs, MKIDs are easy to fabricate and multiplex into...

Modelling the Performance of Single-Photon Counting Kinetic Inductance Detectors

“…As such the true peak value is not easily discerned and the Gaussian width used to calculate energy resolution is likely skewed by the apparent~240-Hz peak. We also note it is likely the distribution includes responses from photons absorbed in the capacitor section of the device where reduced response is observed, as has been seen in similar devices [2].…”

“…However, this is~10 times worse than the theoretical limit imposed by Poisson statistics. Similar experiments working at 1550 nm show the same deviation from theoretical limits achieving energy resolutions of order 220 meV [2]. Still, this is just a factor of~2 worse than transition edge detectors in the same regime [3,4].…”

Development of Microwave Kinetic Inductance Detectors for IR Single-Photon Counting

“…In this paper we describe our preliminary results and we show that the detector can resolve single photon number. The resolution obtained is within a factor two from the best value published in literature [6]. Compared to the latter work the main difference of our design is a larger detector sensitive volume.…”

“…A considerable effort has been devoted to prove theoretically and experimentally that MKIDs can compete with the most sensitive low temperature sensors detecting electromagnetic radiation ranging from the mm waves to the X ray [2]. At 1550 nm single photon number resolving capability has been proved but the energy resolution experimentally demonstrated is still one order of magnitude far from the theoretical limits [5,6]. Therefore, it is reasonable to push for further improvements.…”

Detector-Agnostic Phase-Space Distributions

“…Furthermore, recent advancements in detector technology (see, e.g., Refs. [83][84][85][86]) offer new photon counters to which our detector-agnostic framework is also readily applicable.…”