252 research outputs found
Rare earth spin ensemble magnetically coupled to a superconducting resonator
Interfacing superconducting quantum processors, working in the GHz frequency
range, with optical quantum networks and atomic qubits is a challenging task
for the implementation of distributed quantum information processing as well as
for quantum communication. Using spin ensembles of rare earth ions provide an
excellent opportunity to bridge microwave and optical domains at the quantum
level. In this letter, we demonstrate magnetic coupling of Er spins
doped in YSiO crystal to a high-Q coplanar superconducting
resonator.Comment: 5 pages, 3 figure
Random telegraph fluctuations in granular microwave resonators
Microwave circuit electrodynamics of disordered superconductors is a very active research topic spawning a wide range of experiments and applications. For compact superconducting circuit elements, the transition to an insulating state poses a limit to the maximum attainable kinetic inductance. It is, therefore, vital to study the fundamental noise properties of thin films close to this transition, particularly in situations where a good coherence and temporal stability is required. In this paper, we present measurements on superconducting granular aluminum microwave resonators with high normal state resistances, where the influence of the superconductor to insulator phase transition is visible. We trace fluctuations of the fundamental resonance frequency and observe, in addition to a 1/f noise pattern, a distinct excess noise, reminiscent of a random telegraph signal. The excess noise shows a strong dependency on the resistivity of the films as well as the sample temperature but not on the applied microwave power
Aluminium-oxide wires for superconducting high kinetic inductance circuits
We investigate thin films of conducting aluminium-oxide, also known as
granular aluminium, as a material for superconducting high quality, high
kinetic inductance circuits. The films are deposited by an optimised reactive
DC magnetron sputter process and characterised using microwave measurement
techniques at milli-Kelvin temperatures. We show that, by precise control of
the reactive sputter conditions, a high room temperature sheet resistance and
therefore high kinetic inductance at low temperatures can be obtained. For a
coplanar waveguide resonator with 1.5\,k sheet resistance and a kinetic
inductance fraction close to unity, we measure a quality factor in the order of
700\,000 at 20\,mK. Furthermore, we observe a sheet resistance reduction by
gentle heat treatment in air. This behaviour is exploited to study the kinetic
inductance change using the microwave response of a coplanar wave guide
resonator. We find the correlation between the kinetic inductance and the sheet
resistance to be in good agreement with theoretical expectations.Comment: 16 pages, 7 figure
- …