Abstract
Abstract Following the first demonstration of a levitated nanosphere cooled to the quantum ground state in 2020 (U. Delić, et al. Science, vol. 367, p. 892, 2020), macroscopic quantum sensors are seemingly on the horizon. The nanosphere’s large mass as compared to other quantum systems enhances the susceptibility of the nanoparticle to gravitational and inertial forces. In this viewpoint, we describe the features of experiments with optically levitated nanoparticles (J. Millen, T. S. Monteiro, R. Pettit, and A. N. Vamivakas, “Optomechanics with levitated particles,” Rep. Prog. Phys., vol. 83, 2020, Art no. 026401) and their proposed utility for acceleration sensing. Unique to the levitated nanoparticle platform is the ability to implement not only quantum noise limited transduction, predicted by quantum metrology to reach sensitivities on the order of 10−15 ms−2 (S. Qvarfort, A. Serafini, P. F. Barker, and S. Bose, “Gravimetry through non-linear optomechanics,” Nat. Commun., vol. 9, 2018, Art no. 3690) but also long-lived quantum spatial superpositions for enhanced gravimetry. This follows a global trend in developing sensors, such as cold-atom interferometers, that exploit superposition or entanglement. Thanks to significant commercial development of these existing quantum technologies, we discuss the feasibility of translating levitated nanoparticle research into applications.
Highlights
Quantum mechanics is a cornerstone of modern physics, and quantum behaviours, such as superposition and entanglement, have been extensively observed using subatomic particles, photons, and atoms since the early 1900s [4]
Before explaining the benefits of such a sensing scheme, we first describe the main components of an optomechanical system, and the variety of mechanical modes and optical resonances employed by researchers
A macroscopic quantum state can be created by cooling the c.o.m. motion of a nanoparticle levitated within a harmonic potential, with a mechanical frequency Ωm
Summary
Quantum mechanics is a cornerstone of modern physics, and quantum behaviours, such as superposition and entanglement, have been extensively observed using subatomic particles, photons, and atoms since the early 1900s [4]. The gravitational interaction has so far presented itself as classical [22] It is unknown whether gravity acts as a quantum interaction, for example, via virtual graviton exchange [23], or if gravity is responsible for wave function collapse. Modifications to the Schrödinger equation are studied in the continuous spontaneous localisation (CSL) model [26] This aims to justify quantum wave function collapse by introducing a stochastic diffusion process driven by an unknown noise field that continuously counteracts the spread of the quantum wave function. Through experiment, these collapse models can be falsified to rule out a mass-limit on quantum superpositions due to gravitational or noise induced localization [27,28,29].
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