Proceedings Article | 4 May 2012
KEYWORDS: Photons, Sensors, Superconductors, Resistors, Absorption, Resistance, Single photon detectors, Cryogenics, Quantum efficiency, Nanowires
Standard linear optical detectors have a maximum sensitivity in the few hundreds of photons range, limited by amplifier
noise. On the other hand, single photon detectors, which are the most sensitive detectors, are strongly nonlinear: One or
more photons result in the same output signal. Photon number resolving (PNR) detectors, which have the ability to
discriminate the number of photons in a weak optical pulse, are of great importance in the field of quantum information
processing and quantum cryptography. Moreover, a PNR detector with large dynamic range can cover the gap between
these two detection modes. Such detectors are greatly desirable not only in quantum information science and technology,
but also in any application dealing with low light levels. In this work, we propose a novel approach to photon number
resolving detectors based on spatial multiplexing of nanowire superconducting single-photon detectors. In the proposed
approach, N superconducting nanowires, each connected in parallel to an integrated resistor, are connected in series.
Photon absorption in a nanowire switches its bias current to the parallel resistor, forming a voltage pulse across it. The
sum of these voltages, proportional to the number of absorbed photons, is measured at the output. The use of a cryogenic
preamplifier with high input impedance for the read-out increases the linearity, the signal to noise ratio, and the speed.
With this combination, we expect to be able to count up to few tens of photons with high fidelity, excellent timing
resolution, and very high sensitivity in the telecommunication wavelength range.
