DS10 - Défi de tous les savoirs

Quantum Phase Slips in NanoWires – QPSNanoWires

Submission summary

The celebrated Josephson junction is so far the only known non-linear non-dissipative electronic component. These key properties place it at the heart of essentially all superconducting electronic devices: SQUIDS magnetometers, Josephson Volt standards but also the recently developed quantum information processing circuits or quantum-limited amplifier circuits.

The present project aims at testing the practical feasibility and actual properties of a second non-linear non-dissipative superconducting component which was proposed by Mooij and Nazarov [1] nearly a decade ago. This new component is called a Quantum Phase Slip Junction (QPSJ). It consists of a very thin superconducting wire which is predicted to behave as the exact quantum dual of the Josephson junction. Such duality means that the equations describing the QPSJ and the Josephson junction are formally identical save for charge and phase exchanging roles. In other words, where a Josephson junction coherently superposes many states differing by the number of Cooper pairs having tunneled through the barrier, a QPSJ coherently superposes many states differing by the number of 2pi phase windings along the wire, which can be seen as a superposition of various number of flux quanta having tunneled across the wire. Would such a QPSJ component become actually available, it would be a genuine breakthrough. In particular, it should enable the realization of an experiment dual to the celebrated AC Josephson effect, that would be emblematic of QPSJ physics: Instead of establishing a metrological link between the Volt and the second, this dual experiment would link the Ampere to the second. Likewise, a whole new range of high impedance superconducting circuits (which are presently downright antinomic) would become feasible. This would unquestionably open up a new era for the whole field of superconducting circuits.

Since the proposal of QPSJ came to light, a handful of experiments in different laboratories have attempted investigating the physics of QPSJ. So far they have only partially confirmed the expected characteristics of the component and they have essentially raised more questions than they could answer. More specifically, not only (i) there has been no convincing demonstration of the emblematic dual AC Josephson effect, but (ii) when coherent QPS have been evidenced [2,3], their coherence time was disappointingly low, and (iii) even the very basic prediction of a periodic charge modulation in QPSJs is lacking a clear-cut confirmation [4]. As a result, the present situation is confused: the existence of QPSJ in its full dual glory, is neither established nor ruled out.

We think it is time to address this issue using a more systematic approach than the one-shot experiments that have been performed here and there up to now, and applying the more powerful methods that have been recently developed in the field of circuit QED. The consortium we have gathered has substantial expertise and know-how in all the fields that are relevant for investigating QPSJ. We believe that by combining these expertises and working out systematically the issues starting right form the material properties and the fundamental issues associated with disorder, we should be able to deliver fully working QPSJ devices.

[1] Mooij and Nazarov, Nat. Phys. 2, 169 (2006).
[2] Astafiev et al., Nature 484, 355 (2012),
[3] Peltonen et al. Phys. Rev. B 88, 220506(R) (2013)
[4] Hongisto and Zorin, Phys. Rev. Lett. 108, 097001 (2012)

Project coordination

Philippe Joyez (Service de Physique de l'Etat Condensé)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CEA SACLAY Service de Physique de l'Etat Condensé
Institut Néel CNRS Institut Néel
LPMMC Laboratoire de Physique et Modélisation des Milieux Condensés
SIMaP Laboratoire de Science et Ingénierie des Matériaux et Procédés
Université Paris Sud/CNRS Service de Physique de l'Etat Condensé

Help of the ANR 518,521 euros
Beginning and duration of the scientific project: September 2015 - 48 Months

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