Frequency domain multiplexing readout for large arrays of transition-edge sensors

We report our most recent progress and demonstration of a frequency domain multiplexing (FDM) readout technology for transition-edge sensor (TES) arrays, both of which we have been developing in the framework of the X-IFU instrument on board the future Athena X-ray telescope. Using Ti/Au TES micro-calorimeters, high-Q LC filters and analog...

Bi-Directional Tuning of Josephson Junction Resistance

One of the main components used in superconducting quantum chips is the Josephson junction. Currently when fabricating Josephson junctions, the resistance uniformity at wafer-scale is not optimal. It is also known that an annealing process can alter the junction resistance and with it the qubit frequency. However, laser annealing has only shown...

Coupling Harmonic Oscillators to Superconducting Quantum Interference Cavities

This thesis explores the coupling of microwave cavities containing a Superconducting QUantum Interference Device (SQUID) to a mechanical resonator by means of a flux-mediated optomechanical coupling scheme, and to a Radio-Frequency (RF) circuit via a photon-pressure interaction. While flux-mediated optomechanical systems open the door for the...

Noise Measurements of a Low-Noise Amplifier in the FDM Readout System for SAFARI

The SPICA-SAFARI instrument requires extremely sensitive transition edge sensor (TES) arrays with a noise equivalent power of 2×10-19W/Hz and a readout system with an output noise that is dominated by the detector noise. It is essential to ensure the frequency domain multiplexing (FDM) readout system in SAFARI meets the noise requirement. The...

A Circuit Lagrangian Formulation of Opto-mechanical Coupling between two Electrical Resonators mediated by a SQUID

This thesis analyses a lumped element circuit proposed for an analogue quantum simulation of opto-mechanics. The circuit consists of two resonators, a simple LC-resonator, and a similar resonator in which the inductor is replaced by a SQUID as a flux tuneable inductance. The interaction between the two resonators is established by mutual...

Coherence and nonlinearity in mechanical and josephson superconducting devices

In this thesis, the microwave detection of mechanically compliant objects is investigated. This starts with a system of a suspended metal drum capacitively coupled to a high impedance microstrip resonator. The mechanical non-linear dissipation of the drums is studied. Next, a suspended nanowire coupled to a CPW resonator is studied. With an...

Nanoscale Electrostatic Control of Superconducting Oxide Interfaces

Electronic Transport in Helium Beam Modified Graphene and Ballistic Josephson Junctions

This thesis describes the capabilities of the helium ion microscope (HIM) and that of graphene to explore fundamental physics and novel applications. While graphene offers superior electronic properties, the helium ion microscope allows us to combine imaging and modification of materials at the nanoscale. We used the capabilities of HIM to grow...

Side Gate Tunable Josephson Junctions at the LaAlO₃/SrTiO₃ Interface

Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO₃/SrTiO₃ interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions...

Current-Phase Relation of Ballistic Graphene Josephson Junctions

The current-phase relation (CPR) of a Josephson junction (JJ) determines how the supercurrent evolves with the superconducting phase difference across the junction. Knowledge of the CPR is essential in order to understand the response of a JJ to various external parameters. Despite the rising interest in ultraclean encapsulated graphene JJs,...

Edge transport in the trivial phase of InAs/GaSb

We present transport and scanning SQUID measurements on InAs/GaSb double quantum wells, a system predicted to be a two-dimensional topological insulator. Top and back gates allow independent control of density and band offset, allowing tuning from the trivial to the topological regime. In the trivial regime, bulk conductivity is quenched but...

Suspended carbon nanotubes coupled to superconducting circuits

Carbon nanotubes are unique candidates to study quantum mechanical properties of a nanomechanical resonator. However to access this quantum regime, present detectors are not yet sensitive enough. In this thesis we couple a carbon nanotube CNT mechanical resonator to a superconducting circuit which is a root towards such sensitivity.

Superconducting Quantum Interference based Electromechanical Systems

Mechanical sensors are essential tools for the detection of small forces. This thesis presents the dc SQUID as a detector for the displacement of embedded micromechanical resonators. The device geometry and basic operating principle are described. The SQUID displacement detector reaches an excellent resolution, a factor of 1.5 below the standard...

AC bias characterization of low noise bolometers for SAFARI using an open-loop frequency domain SQUID-based multiplexer operating between 1 and 5 MHz

SRON is developing the Frequency Domain Multiplexing (FDM) read-out and the ultra low NEP TES bolometers array for the infra-red spectrometer SAFARI on board of the Japanese space mission SPICA. The FDM prototype of the instrument requires critical and complex optimizations. For single pixel characterization under AC bias we are developing a...

Low-crosstalk bifurcation detectors for coupled flux qubits

We present experimental results on the crosstalk between two ac-operated dispersive bifurcation detectors, implemented in a circuit for high-fidelity readout of two strongly coupled flux qubits. Both phase-dependent and phase-independent contributions to the crosstalk are analyzed. For proper tuning of the phase the measured crosstalk is 0.1%...

Mechanical systems at the nanoscale

This thesis describes experiments that were done with a wide range of nano(electro)mechanical systems (NEMS). These devices are promising candidates to study mechanics in the quantum regime. The experiments range from AFM measurements on few-layer graphene nanodrums, electrical detection of flexural modes of suspended carbon nanotubes both at...

Simple phase bias for superconducting circuits

A superconducting phase-bias tool, based on a trapped fluxoid in a ring, is proposed and demonstrated. It can provide arbitrary phase values and is simple to fabricate. The phase bias has been realized in two superconducting quantum interference devices, where the critical current versus magnetic flux is shown to be shifted by ?/2 and ?.