Displacemon Electromechanics: How to Detect Quantum Interference in a Nanomechanical Resonator

Abstract

We introduce the "displacemon" electromechanical architecture that comprises a vibrating nanobeam, e.g., a carbon nanotube, flux coupled to a superconducting qubit. This platform can achieve strong and even ultrastrong coupling, enabling a variety of quantum protocols. We use this system to describe a protocol for generating and measuring quantum interference between trajectories of a nanomechanical resonator. The scheme uses a sequence of qubit manipulations and measurements to cool the resonator, to apply two effective diffraction gratings, and then to measure the resulting interference pattern. We demonstrate the feasibility of generating a spatially distinct quantum superposition state of motion containing more than 10 6 nucleons using a vibrating nanotube acting as a junction in this new superconducting qubit configuration.

Creation, storage, and retrieval of an optomechanical cat state

“…These quantities can then be used to give a measure of the effectiveness of the cat-state storage and retrieval. The signatures we examine are the fringe patterns in quadrature probability distributions [41,42], the Wigner function [16,26,27,53] and its negativity [41,45], the off-diagonal terms of the density operator [16], and a variance signature [54][55][56][57][58][59][60][61][62].…”

High-precision gravimeter based on a nano-mechanical resonator hybrid with an electron spin

“…High quality nano(micro)-mechanical resonator is one of the best testbed for fundamental physics [1], such as the macroscopic quantum superpositions [2,3], the gravity induce wavefunction collapse [4], the boundary between quantum and classical regimes [5,6], and etc. It is found that the large quantum superpositions of the nano-mechanical resonator could be realized with the help of cavity modes [7], superconducting circuits [8,9], nitrogen-vacancy centers [10][11][12][13], and etc. The quantum-classical boundaries can be tested in these systems through matter-wave interferometry [8,14,15].…”

Gravity as a classical information channel: consequences and proposals towards detecting wave function collapse

“…A similar time dependent coupling was considered in Ref. [4] by using an external magnetic field. From Fig.…”

“…Ignoring the oscillating terms is the rotating wave approximation [59] and is valid for time scales longer than the mechanical period t ω −1 m as the second two terms average out and (almost) vanish 4 . This interaction generates a two mode squeezed state between the optical field and mechanical oscillator and can be used to entangle the light and the mechanical motion [67,68,69,70].…”

“…The model system consists of a qubit with bare frequency ω q coupled to a mechanical resonator of frequency ω m , where the frequency of the qubit depends on the displacement of the resonator [133,183,184,185,4]. The free Hamiltonian for the system is H/ = ω m b † b + 1 2 ω q (X M )σ z , but we will approximate this by linearizing the ω q (X M ) dependence.…”