AC Josephson effect between two superfluid time crystals

Autti, S.; Heikkinen, P. J.; Mäkinen, J. T.; Volovik, G. E.; Zavjalov, V. V.; Eltsov, V. B.

doi:10.1038/s41563-020-0780-y

Cited by 63 publications

(37 citation statements)

References 37 publications

(53 reference statements)

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“…This state can be thought of as a quantum object that can be used for quantum calculations. Entanglement between two BEC states was suggested by 41 , and the Josephson effect between two BECs was demonstrated in a superfluid He-B recently 42 . The important point is that the mBEC qubit can be used even at room temperature.…”

Section: The Experimenal Resultsmentioning

confidence: 97%

Quantum paradigm of the foldover magnetic resonance

Bunkov

Kuzmichev

Safin

et al. 2021

Sci Rep

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The explosive development of quantum magnonics requires the consideration of several previously known effects from a new angle. In particular, taking into account the quantum behavior of magnons is essential at high excitations of the magnetic system, under the conditions of the so-called phenomenon of “foldover” (bi-stable) magnetic resonance. Previously, this effect was considered in the quasi-classical macrospin approximation. However, at large angles of magnetization precession, the magnon density exceeds the critical value for the formation of a magnon Bose condensate (mBEC). Naturally, this purely quantum phenomenon does not exist in the classical approximation. In addition, mBEC leads to superfluid transfer of magnetization, which suppresses the macroinhomogeneity of the samples. The experiments presented in the article show that quantum phenomena well describes the experimental results of nonlinear magnetic resonance in yttrium iron garnet. Thus, we remove the questions that arose earlier when considering this effect without taking into account quantum phenomena. This discovery paves the way for many quantum applications of supermagnonics, such as the magnetic Josephson effect, long-range spin transport, Q-bits, quantum logic, magnetic sensors, and others.

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Section: The Experimenal Resultsmentioning

confidence: 97%

Quantum paradigm of the foldover magnetic resonance

Bunkov

Kuzmichev

Safin

et al. 2021

Sci Rep

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show abstract

“…This state can be thought of as a quantum object that can be used for quantum calculations. Entanglement between two BEC states was suggested by [41], and the Josephson effect be-tween two BECs was demonstrated in a superfluid 3 He-B recently [42]. The important point is that the mBEC qubit can be used even at room temperature.…”

Section: Resultsmentioning

confidence: 98%

“…A topologically protected mBEC emitting minute-long signals were discovered and explained in [4,5]. This signal can be thought of as a time crystal [6]. It was found that mBEC can be maintained permanently when the relaxation (evaporation) of magnons is compensated by the creation of new magnons from a vacuum using high frequency pumping [7,8].…”

Section: Introductionmentioning

confidence: 99%

Quantum Paradigm of the Foldover Magnetic Resonance

Bunkov

Kuzmichev

Safin

et al. 2020

Preprint

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The explosive development of quantum magnonics requires considering several previously known effects from a new angle. In this article, we revise the phenomenon of "foldover" (bi-stable) magnetic resonance from the point of view of quantum magnonics. The density of magnons under strong excitation can exceed the critical value for the formation of a magnon Bose condensate. Under these conditions, the effect of quantum transport of magnons should be considered. In particular, the effect of spin superfluidity, discovered earlier in super fluid 3He should lead to spatial redistribution of the precessing magnetization. Our experimental results confirm a significant change in properties of the foldover magnetic resonance in yttrium iron garnet (YIG) due to superfluid magnetization transport. This discovery paves the way for many quantum applications of supermagnonics, such as magnetic Josephson effect, long-distance spin transport, Q-bit, quantum logics, magnetic sensors, and others.

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“…The transition from Minkowski spacetime to Euclidean space time, in which the signature of the metric changes, is also possible to probe in superfluids, using the collective modes of Bose-Einstein condensation (BEC) of magnons in the polar phase [113,114]. Let us also mention that the magnon BEC-the spontaneously formed coherent precession of spins-provides the experimental realization of time crystal and time quasicrystal [115,116] following the Wilczek idea [117].…”

Section: Routes To Antispacetime and To Euclidean Spacetimementioning

confidence: 99%