Michael G. Tanner

On-chip quantum interference between silicon photon-pair sources

A silicon-on-insulator device combining two four-wave-mixing photon-pair sources in an interferometer with a reconfigurable phase shifter is used to create and manipulate non-degenerate or degenerate, path-entangled or path-unentangled photon pairs. A quantum interference visibility of nearly 100% is observed on-chip. This device is a first step towards fully integrated quantum technologies.

Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon

Superconducting nanowire single-photon detectors (SNSPDs) have emerged as a highly promising infrared single-photon detector technology. Next-generation devices are being developed with enhanced detection efficiency (DE) at key technological wavelengths via the use of optical cavities. Furthermore, new materials and substrates are being explored for improved fabrication versatility, higher DE, and lower dark counts. We report on the practical performance of packaged NbTiN SNSPDs fabricated on oxidized silicon substrates in the wavelength range from 830 to 1700 nm. We exploit constructive interference from the SiO2/Si interface in order to achieve enhanced front-side fiber-coupled DE of 23.2 % at 1310 nm, at 1 kHz dark count rate, with 60 ps full width half maximum timing jitter.

Kilometre-range, high resolution depth imaging using 1560 nm wavelength single-photon detection

This paper highlights a significant advance in time-of-flight depth imaging: by using a scanning transceiver which incorporated a free-running, low noise superconducting nanowire single-photon detector, we were able to obtain centimeter resolution depth images of low-signature objects in daylight at stand-off distances of the order of one kilometer at the relatively eye-safe wavelength of 1560 nm. The detector used had an efficiency of 18% at 1 kHz dark count rate, and the overall system jitter was ~100 ps. The depth images were acquired by illuminating the scene with an optical output power level of less than 250 µW average, and using per-pixel dwell times in the millisecond regime.

Singlet oxygen luminescence detection with a fiber-coupled superconducting nanowire single-photon detector

We report on the direct monitoring of singlet oxygen luminescence at 1270 nm wavelength using a fiber coupled superconducting nanowire single-photon detector. These results open the pathway to practical dose monitoring in photodynamic therapy.

Quantum interference and manipulation of entanglement in silicon wire waveguide quantum circuits

Integrated quantum photonic waveguide circuits are a promising approach to realizing future photonic quantum technologies. Here, we present an integrated photonic quantum technology platform utilizing the silicon-on- insulator material system, where quantum interference and the manipulation of quantum states of light are demonstrated in components orders of magnitude smaller than previous implementations. Two-photon quantum interference is presented in a multi-mode interference coupler, and the manipulation of entanglement is demonstrated in a Mach-Zehnder interferometer, opening the way to an all-silicon photonic quantum technology platform.

Generation of correlated photon pairs in a chalcogenide As2S3 waveguide

We demonstrate a 1550 nm correlated photon-pair source in an integrated glass platform—a chalcogenide As2S3 waveguide. A measured pair coincidence rate of 80 s−1 was achieved using 57 mW of continuous-wave pump. The coincidence to accidental ratio was shown to be limited by spontaneous Raman scattering effects that are expected to be mitigated by using a pulsed pump source.

High-resolution single-mode fiber-optic distributed Raman sensor for absolute temperature measurement using superconducting nanowire single-photon detectors

We demonstrate a distributed fiber Raman sensor for absolute temperature measurement with spatial resolution on the order of 1 cm at 1550 nm wavelength in a single-mode fiber using superconducting nanowire single-photon detectors. Rapid measurements are shown, with less than 60 s integration period, allowing the demonstration of temperature evolution in an optical fiber recorded at over 100 resolvable, 1.2 cm spaced positions along the fiber simultaneously. This distributed sensor has potential application as a primary reference standard, in which high-accuracy, high-spatial-resolution temperature measurements can be obtained without the need for a separate temperature calibration standard.

Gallium arsenide (GaAs) quantum photonic waveguide circuits

Integrated quantum photonics is a promising approach for future practical and large-scale quantum information processing technologies, with the prospect of on-chip generation, manipulation and measurement of complex quantum states of light. The gallium arsenide (GaAs) material system is a promising technology platform, and has already successfully demonstrated key components including waveguide integrated single-photon sources and integrated single-photon detectors. However, quantum circuits capable of manipulating quantum states of light have so far not been investigated in this material system. Here, we report GaAs photonic circuits for the manipulation of single-photon and two-photon states. Two-photon quantum interference with a visibility of 94.9±1.3% was observed in GaAs directional couplers. Classical and quantum interference fringes with visibilities of 98.6±1.3% and 84.4±1.5% respectively were demonstrated in Mach–Zehnder interferometers exploiting the electro-optic Pockels effect. This work paves the way for a fully integrated quantum technology platform based on the GaAs material system.

Spatial dependence of output pulse delay in a niobium nitride nanowire superconducting single-photon detector

We report on the position-dependent variation in output pulse timing across a superconducting single-photon detector. Our device consists of a single niobium nitride nanowire meander (100 nm width, 4 nm film thickness, 2 mm length). We use a confocal microscope configuration (full width at half maximum-spot size 1.3 μm at 1550 nm wavelength) and a femtosecond laser to study local variations in detection efficiency and output pulse timing. Pulse delays of up to 50 ps across the device correlate to local detection efficiency and resistance variations. This study indicates an underlying mechanism for timing jitter in superconducting nanowire devices.

Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide

We demonstrate photon-pair generation in a reverse proton exchanged waveguide fabricated on a periodically poled magnesium doped stoichiometric lithium tantalate substrate. Detected pairs are generated via a cascaded second order nonlinear process where a pump laser at wavelength of 1.55 μm is first doubled in frequency by second harmonic generation and subsequently downconverted around the same spectral region. Pairs are detected at a rate of 42/s with a coincidence to accidental ratio of 0.7. This cascaded pair generation process is similar to four-wave-mixing where two pump photons annihilate and create a correlated photon pair.