What is it about?

This work addresses the possibility of using the established knowledge of inertial sensors in optical and atom interferometry in the field of quantum circuits using superconductors. We theoretically show that owing to the ability of electrons bound as Cooper pairs to act as phase recorders, interference in a superconducting circuit can be caused by a transverse acceleration. More precisely, considering a superconducting quantum interference device (SQUID), the transverse acceleration to which it is subjected causes the modifications of the phases of the two superconducting order parameters in each arm of the system. This physical phenomenon allows to use a SQUID directly as an accelerometer.

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Why is it important?

The diversity of measurement methods using optics, matter waves, superconducting circuits, offers a rich field of play in quantum technology, which of great interest for advanced scientific research and industry. However, each particular method imposes constraints, which can be cumbersome like kilometers of optical fibers or ultra-low temperature setups. Our theoretical work opens up a promising path as we propose a way forward to addressing issues pertaining to inertial sensors, gravitometry or gravitationnal wave detection using SQUIDs not as magnetometers as part of more elaborate setups but directly as accelerometers. The advantages of using an already well-established superconducting technology on chips for high-precision inertial sensors could be numerous in comparison with current technologies based on optics or cold atoms. In particular, our game-changing results can have an impact in a highly competitive field because of the complexity and costs of the technologies required to reach ultra-high sensitivity levels.

Perspectives

From a more fundamental viewpoint, it is of great interest to study the effects of gravity on conduction electrons in metals and superconductors. Coulomb screening as well as the role played by the lattice ions which may distort the field acting on the electrons result in an effective force that can balance gravity. In fact, only a few works have been devoted to this issue in metals, like those of Tolman in 1913 and 1916, and those of Wittenborn and Fairbank in 1967 and in 1968; and the theoretical explanations do not yet rest on very firm grounds. No experimental gravity measurement effects on Cooper pairs in superconductors have been reported, so whether screening effects occur in a superconductor given that the Cooper pairs have some coherence and penetration lengths, remains an open question. Only adequate experiments could answer on this issues. In this respect, our work dusts off the past achievements and aims to foster new experimental activities in this field.

Henni Ouerdane

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This page is a summary of: SQUID-based interferometric accelerometer, Applied Physics Letters, October 2022, American Institute of Physics, DOI: 10.1063/5.0126680.
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