High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared

Abstract

We report on high-efficiency superconducting nanowire single-photon detectors based on amorphous WSi and optimized at 1064 nm. At an operating temperature of 1.8 K, we demonstrated a 93% system detection efficiency at this wavelength with a dark noise of a few counts per second. Combined with cavity-enhanced spontaneous parametric down-conversion, this fiber-coupled detector enabled us to generate narrowband single photons with a heralding efficiency greater than 90% and a high spectral brightness of 0.6 × 10 4 photons/(s·mW·MHz). Beyond single-photon generation at large rate, such high-efficiency detectors open the path to efficient multiple-photon heralding and complex quantum state engineering.The near-infrared wavelength range has been an important playground for a large community in quantum optics, in particular at λ = 1064 nm. At this wavelength that corresponds to Nd:YAG lasers, narrow-linewidth and ultra-stable lasers are available, and also ultralowloss optical coatings and photodiodes with close-to-unity efficiency. Pioneering [1] and world-record [2] demonstrations of squeezed light [3] have been performed at this wavelength, as well as quantum teleportation [4] and enhanced quantum metrology, including for gravitational wave detection [5]. In contrast to these realizations, the preparation of single-photon states or more complex states involving larger photon-number components generally requires single-photon detections to herald their preparations [6][7][8]. The efficient detection of single photons is therefore a fundamental and demanding requisite for these investigations [9]. This is particularly true for multiple heraldings, a challenging trend for developing novel quantum state engineering capabilities and further scalability in quantum networks [10].However, detecting efficiently single photons at λ = 1064 nm has been a long-standing issue. Avalanche photodiodes (APDs) based on Silicon are limited to a few percent quantum efficiency. InGaAs/InP ones, even though large improvements have been obtained in the recent years with these devices, still exhibit limited efficiency for this specific wavelength and often suffer from large dark count rates if used in free-running mode. In this wavelength range, the first generation of NbN superconducting nanowire single-photon detectors [11] (SNSPDs) was typically limited to 20-30% efficiencies.Recently, the development of SNSPDs based on tungsten silicide (WSi) [12,13] enabled to outperform other * These authors contributed equally.† julien.laurat@upmc.fr infrared single-photon detectors, despite great progresses with NbN-based devices [14,15]. In addition to a better internal efficiency than other materials, the amorphous nature of WSi facilitates the fabrication of large sensitive area and the embedding of the material inside an optical stack to enhance absorption. System detection efficiency (SDE) greater than 90% has been achieved in the wavelength range λ = 1520−1610 nm [16]. Efficient operation above 2 K has also been demonstrated at 1310 nm [17].In...

Demonstration of Einstein-Podolsky-Rosen Steering Using Hybrid Continuous- and Discrete-Variable Entanglement of Light

“…It relies on two optical parametric oscillators (OPO), one located with each party, pumped below threshold by a continuous-wave frequency-doubled Nd:YAG laser. The first OPO, based on a type-II phasematched KTP crystal, is used as the DV source and enables on its own the generation of single photons, with a heralding efficiency above 90%, using high-efficiency superconducting nanowire single-photon detectors [35]. The second OPO is based on a PPKTP crystal and generates a 3-dB-squeezed vacuum state.…”

Hybrid Rabi interactions with traveling states of light

“…Alternatively as in figure 1(b), a single photon entangled state (or a dual-rail qubit) may be injected into the lower arm for the physically swapped entangled states from TMSV's case. A high-quality single photon state can be generated from weak two-mode parametric squeezing processes heralded by a SPD in one of the modes [87,88]. After a beam splitter D, this single photon is split into an entangled state…”

Loop-based subtraction of a single photon from a traveling beam of light

“…(1 − η) n |n 1 n| andΠ • 1 =1 −Π • 1 for a realistic detector with nonunit quantum efficiency η. We neglect the dark counts as they are negligibly small for high quality superconducting detectors [34]. When the beam splitter is strongly unbalanced and the amplitude transmissivity t = cos κ is close to one, the unitary operator can be replaced by its Taylor expansion up to the first order and the output state can be approximated tô…”