Platform for Measurements of the Casimir Force between Two Superconductors

Abstract

Several experimental demonstrations of the Casimir force between two closely spaced bodies have been realized over the past two decades. Extending the theory to incorporate the behavior of the force between two superconducting films close to their transition temperature has resulted in competing predictions. To date, no experiment exists that can test these theories, partly due to the difficulty in aligning two superconductors in close proximity, while still allowing for a temperature-independent readout of the arising force between them. Here we present an on-chip platform based on an optomechanical cavity in combination with a grounded superconducting capacitor, which overcomes these challenges and opens up the possibility to probe modifications to the Casimir effect between two closely spaced, freestanding superconductors as they transition into a superconducting state. We also perform preliminary force measurements that demonstrate the capability of these devices to probe the interplay between two widely measured quantum effects: Casimir forces and superconductivity.

Coupling microwave photons to a mechanical resonator using quantum interference

“…The mechanical oscillator is a large aluminum beam and is suspended as result of releasing part of the superconducting loop forming the SQUID by removing the underlying silicon substrate in an isotropic reactive ion etching process 31 . The beam has a total mass pg and its fundamental out-of-plane mode oscillates at a frequency MHz with an intrinsic mechanical damping rate of Hz or quality factor , which is exceptionally high for a mechanical oscillator made from a sputter-deposited metal film.…”

Quanten‐mechanisch im Wortsinne

“…In Delft haben wir ein optomechanisches System verwendet, um die Quantenkräfte zu bestimmen, die aufgrund der Vakuumfluktuationen zwischen zwei Oberflächen über sehr kurze Distanzen von etwa hundert Nanometer entstehen – der berühmte Casimir‐Effekt (s. Physik in unserer Zeit 2005 , 36 (2), 85). Dabei war es erstmals möglich, eine solche Messung an einem supraleitenden Material über‐ und unterhalb der kritischen Temperatur durchzuführen [15].…”

Fabrication of on-chip probes for double-tip scanning tunneling microscopy

“…Reactive ion etching is often a combination of chemical reactions, where F − ions react with Si, and ion bombardment, where the ions are accelerated by a bias into the sample, which removes material. Here, however, to prevent any anisotropy in the etch, we apply a bias except for during a short ignition pulse <1 s to ignite the plasma, resulting in a predominantly isotropic Si etch 33 b The pattern is then transferred into the SiN. c The resist is cleaned thoroughly, and a fresh layer of photoresist is applied to protect against debris from dicing (not displayed for clarity).…”