Duality and the charge quantum interference device

The duality between phase and charge in superconducting devices holds the promise of new electronic devices and of the realisation of a robust quantum current standard, capable of disseminating the new definition of the... [ view full abstract ]

The duality between phase and charge in superconducting devices holds the promise of new electronic devices and of the realisation of a robust quantum current standard, capable of disseminating the new definition of the ampere, based on effects exactly dual to those that enable the Josephson voltage standard [1]. We present the experimental realisation of a Charge Quantum Interference Device (CQUID, right figure) [2], a quantum sensor dual to the Superconducting Quantum Interference Device (SQUID, left figure). The CQUID is made out of 3.3 nm thin atomic layer deposited (ALD) highly disordered superconducting niobium nitride film close to the superconductor-insulator transition. Two narrow constrictions in a wire made from this film are connected in series via a small superconducting island and act as barriers for flux tunnelling across the superconductor, carried by coherent quantum phase slips (CQPS) of the superconducting order parameter [3]. The CQUID becomes a charge sensitive quantum interferometer based on the Aharonov-Casher effect: We demonstrate control of flux tunnelling (phase slip) interference across multiple CQPS junctions in a continuous superconductor by an induced charge on the island. This is the exact duality to the SQUID, which is a specific realisation of the Aharonov-Bohm effect, where the high sensitivity to magnetic flux stems from the interference of Cooper-pair tunnelling across a continuous insulator in the Josephson junction.

[1] J. E. Mooij and Y. V. Nazarov, Superconducting nanowires as quantum-phase slip junctions, Nature Physics 2, 169 (2006).
[2] S. E. de Graaf et al. Charge quantum interference device, accepted in Nature Physics (2018). 
[3] O. V. Astafiev et al., Coherent quantum phase slip, Nature 484, 355 (2012).