Dr. Boon Kok Tan

Abstract:

In 2021 the Quantum Sensors for the Hidden Sector (QSHS) collaboration was founded in the UK and received funding to develop and demonstrate quantum devices with the potential to detect hidden sector particles in the μeV to 100 μeV mass window. The collaboration has been developing a range of devices. It is building a high-field, low-temperature facility at the University of Sheffield to characterise and test the devices in a haloscope geometry. This paper introduces the collaboration's motivation, aims, and progress.

Abstract:

We report the design of a compact dual-polarization on-chip superconductor–insulator–superconductor receiver for array applications. The planar-circuit receiver chip is comprised of the entire radio frequency (RF) signal processing chain with three main circuit components alongside some auxiliary circuits: (1) a polarization splitting 4-probe orthomode transducer (OMT) that couples the RF and local oscillator signal from free space to the chip via a drilled feedhorn; (2) two hybrids that recombine the power of each polarization from the two sets of orthogonal OMT probes; and (3) twin-junction Nb/AlOx/Nb mixers that downconvert the recombined signals to the intermediate frequency. We ensure that the four side walls of each pixel are free from obscuration, using only the top and bottom of the pixel for various connections. Consequently, the design is extendable to a large format array. In this paper, we present the detailed design of the on-chip receiver, including extensive heterodyne simulations and its potential extension into a large format array.

Abstract:

We present the design of a superconductor-insulator-superconductor (SIS) mixer fed with a 2-probe antenna mounted in a circular waveguide, hence avoiding the need for a rectangular waveguide that is often difficult to machine at high millimetre and sub-millimetre frequencies. The mixer is designed to operate from 275–375 GHz, covering a similar frequency range to the HARP-B receiver of the James Clerk Maxwell Telescope. Each antenna probe is connected to a separate but identical mixer circuit comprising three SIS junctions connected in series to reduce the parasitic capacitance, and the relevant tuning circuits and RF chokes. The down-converted IF power at the output of each mixer branch is expected to be combined using either a microwave Wilkinson power combiner or a 180◦ hybrid, to recover the full signal strength. In this paper, we present in the detail the electromagnetic simulations of each RF component making up the mixer chip, as well as the performance of the entire 2-probe mixer including the RF and IF performance predicted using SuperMix, a software package developed based on Tucker’s theory of quantum mixing. Finally, we show how such circular waveguide SIS mixers can be easily populated onto a simple split-block to form a 16-pixel array. © 2022 32nd International Symposium of Space Terahertz Technology, ISSTT 2022 All rights reserved.

Abstract:

Travelling wave parametric amplifiers (TWPAs) made from highly nonlinear reactive superconducting thin films have been demonstrated to be a potentially viable quantum-noiselimited amplifier technology for various fundamental physics platforms, including microwave/millimetre (mm)/sub-mm astronomy, dark matter search experiments, absolute neutrino mass determinations, and qubit readout platforms. To date, only a limited number of successful kinetic inductance (KI-)TWPA devices have been reported, with the majority of them fabricated from niobium titanium nitride (NbTiN) thin films; although in principle, any highly nonlinear low loss superconducting film can be used to construct a KITWPA. In this proceeding, we explore the suitability of using a different type of superconducting film, titanium nitride (TiN) for such application. We report on the detailed analysis of the nonlinear behaviour of TiN films to ascertain the film’s suitability for application as KITWPA. We experimentally characterised TiN transmission lines at cryogenic temperatures to compare the results predicted with electromagnetic simulations. This characterisation and analysis allows us to understand the fundamental physics governing the behaviour of the TiN films, their merits and limitations, and whether they are well suited for applications as KITWPAs.