Ultranarrow-linewidth levitated nano-oscillator for testing dissipative wave-function collapse

Abstract

Levitated nano-oscillators are promising platforms for testing fundamental physics and quantum mechanics in a new high mass regime. Levitation allows extreme isolation from the environment, reducing the decoherence processes that are crucial for these sensitive experiments. A fundamental property of any oscillator is its linewidth and mechanical quality factor Q. Narrow linewidths in the microhertz regime and mechanical Q's as high as 10 12 have been predicted for levitated systems. The insufficient long-term stability of these oscillators has prevented direct measurement in high vacuum. Here we report on the measurement of an ultranarrow linewidth levitated nano-oscillator, whose width of 81 ± 23 μHz is only limited by residual gas pressure at high vacuum despite residual variations of the trapping potential. This narrow linewidth allows us to put new experimental bounds on dissipative models of wave-function collapse including continuous spontaneous localization and Diósi-Penrose and illustrates its utility for future precision experiments that aim to test the macroscopic limits of quantum mechanics.

Ultralow Mechanical Damping with Meissner-Levitated Ferromagnetic Microparticles

“…The damping time τ is comparable with recent results obtained with optical [26], diamagnetic [32] and electrical [29] levitation, with the advantage of lower temperature. In terms of the thermal noise factor, our magnetically levitated particles achieve T /τ ≈ 10 −4 K/s, which is already at the state of the art for micro/nanosystems.…”

“…By assuming a thermal noise limited operation, the microparticle described in this work would feature a force noise spectral density S f ≈ 1 aN/ √ Hz for the z mode. This noise level has been achieved so far only with much smaller masses [23,26,29]. Therefore, our micromagnet would be suitable to detect forces which scale with the size or with the mass of the particle.…”

“…Due to the simultaneous combination of ultralow damping and low temperature, this system features very low thermal noise, opening the way to a number of extreme sensing applications, to detect weak forces, acceleration, torque and magnetic fields. For instance, this technology can be exploited in the search for exotic effects arising from new physics [11,22,26,54], measurements of the gravitational constant G with small test masses [55] and tests of collapse models [12,18,29]. In the context of quantum technologies, ultraisolated micromagnets can be strongly coupled to single spins [31], superconducting circuits [27] or acoustomagnonic modes [37], enabling unconventional quantum protocols and, on more fundamental level, tests of quantum mechanics at mesoscopic scale [4].…”

“…This suggests that different levitation methods, such as Paul traps [28][29][30][31], or magnetic traps [32][33][34][35] could outperform optical levitation in applications requiring the lowest possible noise level. In particular, magnetic levitation appears very promising because of the unique combination of two properties: a completely passive trapping by static magnetic fields, and the possibility of using SQUIDs to detect the motion with ultralow power dissipation.…”

Trends in Quantum Nanophotonics

“…[ 154 ] Not surprisingly, the detection requirements are very demanding; a careful analysis of a variety of electrical and optical detection techniques has recently been undertaken. [ 155 ] Noninterferometric tests of collapse models have recently been undertaken with nanocantilevers [ 156 ] and levitated nanoparticles, [ 157 ] resulting in more stringent bounds on parameters associated with these proposed collapse models. There also exist proposals for searching for signatures of semiclassical gravity, for example, as described by the Schrodinger–Newton equation, in the modification of the noise spectrum of an optomechanical system.…”