Saeedeh Jahanmirinejad

Waveguide superconducting single-photon detectors for integrated quantum photonic circuits

The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (∼20%) at telecom wavelengths, high timing accuracy (∼60 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators.

Photon-number resolving detector based on a series array of superconducting nanowires

We present the experimental demonstration of a superconducting photon number resolving detector. It is based on the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. The device provides a single voltage readout, proportional to the number of photons detected in distinct nanowires. Clearly separated output levels corresponding to the detection of n = 1−4 photons are observed in a 4-element detector fabricated from an NbN film on GaAs substrate, with a single-photon system quantum efficiency of 2.6% at λ = 1.3 μm. The series-nanowire structure is promising in view of its scalability to large photon numbers and high efficiencies.

Physics and application of photon number resolving detectors based on superconducting parallel nanowires

The parallel nanowire detector (PND) is a photon number resolving (PNR) detector that uses spatial multiplexing on a subwavelength scale to provide a single electrical output proportional to the photon number. The basic structure of the PND is the parallel connection of several NbN superconducting nanowires (?100?nm wide, a few nm thick), folded in a meander pattern. PNDs were fabricated on 3?4?nm thick NbN films grown on MgO?(TS = 400??C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture. The device performance was characterized in terms of speed and sensitivity. PNDs showed a counting rate of 80?MHz and a pulse duration as low as 660?ps full-width at half-maximum (FWHM). Building the histograms of the photoresponse peak, no multiplication noise buildup is observable. Electrical and optical equivalent models of the device were developed in order to study its working principle, define design guidelines and develop an algorithm to estimate the photon number statistics of an unknown light. In particular, the modeling provides novel insight into the physical limit to the detection efficiency and to the reset time of these detectors. The PND significantly outperforms existing PNR detectors in terms of simplicity, sensitivity, speed and multiplication noise.

Waveguide photon-number-resolving detectors for quantum photonic integrated circuits

Quantum photonic integration circuits are a promising approach to scalable quantum processing with photons. Waveguide single-photon-detectors (WSPDs) based on superconducting nanowires have been recently shown to be compatible with single-photon sources for a monolithic integration. While standard WSPDs offer single-photon sensitivity, more complex superconducting nanowire structures can be configured to have photon-number-resolving capability. In this work, we present waveguide photon-number-resolving detectors (WPNRDs) on GaAs/Al0.75Ga0.25As ridge waveguides based on a series connection of nanowires. The detection of 0–4 photons has been demonstrated with a four-wire WPNRD, having a single electrical read-out. A device quantum efficiency of ∼24% is reported at 1310 nm for the transverse electric polarization.

Proposal for a superconducting photon number resolving detector with large dynamic range

We propose a novel photon number resolving detector structure with large dynamic range. It consists of the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. Photon absorption in a wire switches its current to the parallel resistor producing a voltage pulse and the sum of these voltages is measured at the output. The combination of this structure and a high input impedance preamplifier result in linear, high fidelity, and fast photon detection in the range from one to several tens of photons.

Superconducting series nanowire detector counting up to twelve photons

We demonstrate a superconducting photon-number-resolving detector capable of resolving up to twelve photons at telecommunication wavelengths. It is based on a series array of twelve superconducting NbN nanowire elements, each connected in parallel with an integrated resistor. The photon-induced voltage signals from the twelve elements are summed up into a single readout pulse with a height proportional to the detected photon number. Thirteen distinct output levels corresponding to the detection of n = 0-12 photons are observed experimentally. A detailed analysis of the linearity and of the excess noise shows the potential of scaling to an even larger dynamic range.

Photon-number-resolving superconducting nanowire detectors

In recent years, photon-number-resolving (PNR) detectors have attracted great interest, mainly because they can play a key role in diverse application fields. A PNR detector with a large dynamic range would represent an ideal photon detector, bringing the linear response of conventional analogue detectors down to the single-photon level. Several technologies, such as InGaAs single photon avalanche detectors (SPADs), arrays of silicon photomultipliers, InGaAs SPADs with self-differencing circuits and transition edge sensors have shown photon number resolving capability. Superconducting nanowires provide free-running single-photon sensitivity from visible to mid-infrared frequencies, low dark counts, excellent timing resolution (<60 ps) and short dead time (~10 ns), at an easily accessible temperature (2–3 K), but they do not inherently resolve the photon number. In this framework, PNR detectors based on arrays of superconducting nanowires have been proposed. In this article we describe a number of methods and device configurations that have been pursued to obtain PNR capability using superconducting nanowire detectors.

Waveguide superconducting single-photon autocorrelators for quantum photonic applications

We report a novel component for integrated quantum photonic applications, a waveguide single-photon autocorrelator. It is based on two superconducting nanowire detectors patterned onto the same GaAs ridge waveguide. Combining the electrical output of the two detectors in a correlation card enables the measurement of the second-order correlation function g(2) (τ), which realizes the functionality of a Hanbury-Brown and Twiss experiment in a very compact integrated device. Each detector shows a polarization-independent quantum efficiency of ~0.5-1% at 1300 nm. This autocorrelator represents a key building block for quantum photonic integrated circuits including single-photon sources and linear optics.

Superconducting nanowires connected in series for photon number resolving functionality

The experimental demonstration of a superconducting photon-number-resolving detector, based on the series connection of N superconducting nanowires, is presented. An integrated resistor is connected in parallel to each section of the device that provides in this way a single voltage-readout, proportional to the number of photons detected in distinct nanowires. As a proof of principle a four element detector has been fabricated from an NbN film on a GaAs substrate and fully characterized. Clearly separated output levels corresponding to the detection of n = 1 – 4 photons are observed achieving a single-photon system quantum efficiency of 2.6% at λ=1.3 μm. In order to demonstrate the potential scalability of the series-nanowire detector to a larger number of photons, we report our preliminary results in the characterization of detectors fabricated with 8 and 12 pixels. Clear evidence of n= 1-8 photon absorption in the 8-pixel detector has been achieved.

Quantum integrated photonics on GaAs

We present a quantum integrated photonics platform on GaAs including waveguide single-photon sources and detectors on the same chip.