Colloquium: Quantum interference of clusters and molecules

Abstract

We review recent progress and future prospects of matter wave interferometry with complex organic molecules and inorganic clusters. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. We discuss the theoretical concepts underlying these experiments and the experimental challenges. This includes optimizing interferometer designs as well as understanding the role of decoherence. The high sensitivity of matter wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles. We conclude by investigating the prospects for probing the quantum superposition principle in the limit of high particle mass and complexity.

Quantum-limited estimation of continuous spontaneous localization

“…The inspection of Eq. (8) shows that the latter is only coupled to the position of the mechanical oscillator, which would not be sufficient to infer its energy directly. We thus proceed to a full-fledged analysis of the results achievable through the use of quantum estimation theory in the context set by this paper.…”

“…The strength of this effect should increase with the size (mass) of the system, leaving microscopic (macroscopic) systems fully within the quantum (classical) realm. The key difference between CMs and standard quantum mechanics is that in the framework entailed by the former, perfectly isolated macroscopic objects would continue to act classically.Among the proposals put forward so far to test (or rule out) some of the currently formulated CMs [8][9][10], those based on the experimental platform of cavity optomechanics offer features of undemanding scalability of the mass of the system to be probed and high-sensitivity of measurement. Most remarkably, at variance with standardly pursued approaches [11], they bypass the need for the construction and quantum-limited management of large interferometers [12,13].…”

“…Among the proposals put forward so far to test (or rule out) some of the currently formulated CMs [8][9][10], those based on the experimental platform of cavity optomechanics offer features of undemanding scalability of the mass of the system to be probed and high-sensitivity of measurement. Most remarkably, at variance with standardly pursued approaches [11], they bypass the need for the construction and quantum-limited management of large interferometers [12,13].…”

Double-Slit Interference Pattern for a Macroscopic Quantum System

“…Hornberger et al investigated the effect of environment on interference pattern of fullerenes as a macro-molecule [6]. Also, Hornberger and others studied quantum interferenece of the clusters in experiment [7]. Gerlich and others showed the quantum diffraction of large organic molecules [8].…”

Generating the Schrödinger cat state in a nanomechanical resonator coupled to a charge qubit

“…Generating large quantum superposition of the macroscopic objects is an essential task in the field of the macroscopic quantum mechanics [3][4][5][6], which provides a good platform to understand the mechanism of decoherence in macroscopic objects [7,8], to check the scope of application of quantum theory [9] and to observe the transition between quantum and classical physics [10]. To this end, the large quantum superposition, like the Schrödinger cat state (simply called 'cat state' in the following), has been realized in various systems, such as trapped ions [11], photons [12], superconducting qubits [13], macroscopic current [14], and NAMR [15].…”