On-chip coherent detection with quantum limited sensitivity

Abstract

While single photon detectors provide superior intensity sensitivity, spectral resolution is usually lost after the detection event. Yet for applications in low signal infrared spectroscopy recovering information about the photon’s frequency contributions is essential. Here we use highly efficient waveguide integrated superconducting single-photon detectors for on-chip coherent detection. In a single nanophotonic device, we demonstrate both single-photon counting with up to 86% on-chip detection efficiency, as well as heterodyne coherent detection with spectral resolution f/∆f exceeding 1011. By mixing a local oscillator with the single photon signal field, we observe frequency modulation at the intermediate frequency with ultra-low local oscillator power in the femto-Watt range. By optimizing the nanowire geometry and the working parameters of the detection scheme, we reach quantum-limited sensitivity. Our approach enables to realize matrix integrated heterodyne nanophotonic devices in the C-band wavelength range, for classical and quantum optics applications where single-photon counting as well as high spectral resolution are required simultaneously.

Heterodyne spectrometer sensitivity limit for quantum networking

“…This notional configuration yields 4 × 10 −8 noise counts per mode. Interestingly, there was a demonstration with SNSPDs integrated into a heterodyne spectrometer [4]. This device showed detection at low light levels (about 1000 photons/sec) for a very narrowband light source (about 1 kHz), which agrees with the shot-noise detection limit discussed here.…”

“…Heterodyne spectrometers have the benefit of the frequency resolution being primarily limited only by the local oscillator bandwidth and stability, assuming the post-processing electronics have the required precision. Because of this, heterodyne spectrometers have been demonstrated with resolution < 125 MHz (< 1 pm at 1550 nm) [3][4][5][6][7]. The sensitivity of these heterodyne spectrometers on the other hand has not been as impressive, often not much below -60 dBm [8,9] when using photodiodes.…”

“…The sensitivity of these heterodyne spectrometers on the other hand has not been as impressive, often not much below -60 dBm [8,9] when using photodiodes. Using superconducting-nanowire single-photon detectors, -126 dBm has been shown for narrowband signals [4]. Others have shown that there are practical and theoretical limits to the sensitivity of heterodyne spectrometer and discussed them in the context of astronomical observation [10,11] and laser side-band characterization [12].…”

Thin‐Film‐Based Integrated High‐Transition‐Temperature Superconductor Devices

“…Detectors in the telecommunication wavelength range are traditionally of interest for long‐range quantum key distribution applications . Many other quantum applications also require on‐chip photodetection and counting such as those with integrated optical waveguide platforms and photon correlation measurements 1 shows a list of reported single‐photon detector technologies with spectral operating range, efficiency, and other important factors.…”