SuperfluidHe4interferometer operating near2K

Abstract

Matter-wave interferometers reveal some of the most fascinating phenomena of the quantum world 1 . Phase shifts due to rotation (the Sagnac effect) for neutrons 2 , free atoms 3 and 4, 5 superfluid 3 He reveal the connection of matter waves to a non-rotating inertial frame. In addition, phase shifts in electron waves due to magnetic vector potentials (the Aharonov-Bohm effect 6 ) show that physical states can be modified in the absence of classical forces. We report here the observation of interference induced by the Earth's rotation in superfluid 4 He at 2 K, a temperature 2000 times higher than previously achieved with 3 He. This interferometer, an analog of a dc-SQUID, employs a recently reported phenomenon wherein superfluid 4 He exhibits quantum oscillations in an array of sub-micron apertures 7,8 . We find that the interference pattern persists not only when the aperture array current-phase relation is a sinusoidal function characteristic of the Josephson effect, but also at lower temperatures where it is linear and oscillations occur by phase slips 9,10 . The modest requirements for the interferometer (2 K cryogenics and fabrication of apertures at the level of 100nm) and its potential resolution suggest that, when engineering challenges such as vibration isolation are met, superfluid 4 He interferometers could become important scientific probes. Superfluid4 He is described by a macroscopic wave function which includes a phase φ that can vary in time and space. Our new interferometer is based on a recently reported phenomenon wherein an array of 4225 (65 2 ) small apertures coupling together two reservoirs of superfluid 4 He exhibits fluid oscillations at the Josephson frequency.The superfluid current I through an aperture array is a function of the fluid phase difference φ Δ between one side of the array and the other. This

Coupling and proximity effects in the superfluid transition in 4He dots

“…Furthermore, weak links and coupling between two regions of 4 He cannot be achieved through any material other than 4 He. We can, however, take advantage of the growth of the correlation length with temperature T and critical exponent ν, ξ = ξ 0 |1 − T /T λ | −ν ≡ ξ 0 t −ν near the transition temperature T λ and construct apertures whereby analogous Josephson effects can be realized 10,11 .…”

“…Furthermore, weak links and coupling between two regions of 4 He cannot be achieved through any material other than 4 He. We can, however, take advantage of the growth of the correlation length with temperature T and critical exponent ν, ξ = ξ 0 |1 − T /T λ | −ν ≡ ξ 0 t −ν near the transition temperature T λ and construct apertures whereby analogous Josephson effects can be realized 10,11 .We are unaware of any theory that describes the effects on thermodynamic properties of a 'grain' or dot of helium due to a coupling to another dot through a weak link, or, for that matter, how this coupling is affected by the geometry or 'strength' of this link. This question arose while attempting to verify finite-size scaling for zero-dimensional crossover 12 .…”

Comparative analysis of optical-physical schemes of gyroscopes based on macroscopic quantum effects of superfluid helium isotopes (3He &4He)

“…The critical velocity measurement is a rotation sensing method in this configuration. This experiment was carried out with superfluid 4 He at T ~ 12 mK. An experiment with better accuracy has been reported by the same authors [6], and independent corroboration has been provided by Schwab et al [7].…”

“…Rotation-induced velocity [5] was first measured with a 4 He superfluid rf-SQUID by O. Avenel and E. Varoquaux [1]. The basic structure has two superfluid reservoirs shunted by a larger tube and coupled to a diaphragm to form a hydrodynamic resonator.…”

Repulsive gravitational effect of a quantum wave packet and experimental scheme with superfluid helium

“…Thus, it is unlikely that we will find evidence to verify or falsify this anomalous acceleration without future experiments. Apart from atom interferometry, the measurement of acceleration due to gravity using Bloch oscillation [32][33][34][35] for cold atoms in optical lattices, superfluid helium interferometry [36], free-fall absolute gravimeters [37][38][39], and superconducting gravimeters [40][41][42][43] provides other methods to test the abnormal gravitational effect. In particular, the standard deviation of free-fall absolute gravimeters in the present technique is roughly 10 −8 m/s 2 ; superconducting gravimeters have achieved sensitivities of one thousandth of one billionth (10 −12 ) of the Earth's surface gravity.…”