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arXiv:2607.20195

Mesoscopic mechanical superpositions by gluing individual quantum systems

Thiago Guerreiro

quant-phSubmitted Jul 22, 2026• Announced Jul 23, 2026• 0 citations
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Abstract

We propose a protocol for preparing mechanical Schrödinger kittens -- mesoscopic quantum superpositions of coherent motional states of an optically levitated nanoparticle -- by adhering single electron time-bin states to its surface. Over short protocol timescales, coherence of the mesoscopic superposition survives the dominant decoherence mechanisms afflicting levitated systems, and can be observed by varying the phase of the time-bin electrons. Interference fringes can be detected with real-time, near-Heisenberg limited interferometry of photons scattered from the particle. This approach eliminates the need for coherent state expansion, dark potentials, and particle release-and-recapture mechanisms, providing a new route to test quantum mechanics in unprecedented scales.

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We propose a protocol for preparing mechanical Schrödinger kittens -- mesoscopic quantum superpositions of coherent motional states of an optically levitated nanoparticle -- by adhering single electron time-bin states to its surface. Over short protocol timescales, coherence of the mesoscopic superposition survives the dominant decoherence mechanisms afflicting levitated systems, and can be observed by varying the phase of the time-bin electrons. Interference fringes can be detected with real-time, near-Heisenberg limited interferometry of photons scattered from the particle. This approach eliminates the need for coherent state expansion, dark potentials, and particle release-and-recapture mechanisms, providing a new route to test quantum mechanics in unprecedented scales.
We propose a scheme for generating high-mass quantum superposition states of an optically precooled, levitated nanoparticle through electron diffraction at its subnanometer crystal lattice. When a single electron undergoes Bragg diffraction at a free-falling nanoparticle, momentum conservation implies that the superposition of Bragg momenta is imprinted onto the relative coordinate between electron and nanoparticle, which entangles their wave functions. By imaging the electron interferogram, one maps the nanoparticle state onto a superposition of Bragg momenta, as if it was diffracted by its own lattice. This results in a coherent momentum splitting approximately 1000 times greater than what is achievable with two-photon recoils in conventional standing-wave gratings. Self-interference of the nanoparticle can thus be observed within drastically shorter free-fall times in a time-domain Talbot interferometer configuration, significantly relaxing source requirements and alleviating decoherence from environmental factors such as residual gas and thermal radiation. Shorter interference times also allow for a recapture of the nanoparticle within its initial trapping volume, facilitating its reuse in many rapid experimental duty cycles. This opens new possibilities for experimental tests of macroscopic quantum effects within a transmission electron microscope.
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ABSTRACT Levitodynamics, i.e., the levitation of objects of mesoscopic size has made huge progress in the last decade allowing to address some questions of fundamental physics for the first time. It has become possible to cool a levitated particle of mesoscopic size down to its motional ground state and to observe its motion driven by quantum fluctuations. This defines a quantum system that is ideally suited for an analysis within Nelson's stochastic mechanics approach to quantum mechanics, which allows for a dynamic description of individual particle paths. In good approximation, a levitated nanoparticle is a quantum harmonic oscillator. The coherent states of such an oscillator are superpositions of classical paths and the stochastic ground state process. They are exact solutions not only of the Schrödinger equation but also of the quantum Hamilton equations of Nelson's stochastic mechanics, and they are amenable to path simulations. All model parameters are typically available from experiment. Analyzing the quantum motion of the levitated nanoparticle in terms of the coherent states of a quantum harmonic oscillator allows for a quantitative prediction of the experimentally measured power spectral density of its position fluctuations and predicts new experimentally accessible measures for the mean number of phonons present in the center of mass motion. It also explains the observed phase space trajectory of the nano‐particle during cooling.
We introduce and theoretically analyze a scheme to prepare and detect non-Gaussian quantum states of an optically levitated particle via the interaction with light pulses that generate cubic and inverted potentials. We show that this approach allows to operate on sufficiently short time- and length scales to beat decoherence in a regime accessible in state-of-the-art experiments. Specifically, we predict the observation of single-particle interference of a nanoparticle with a mass above 10 8 atomic mass units delocalized by several nanometers, on timescales of milliseconds. The proposed experiment uses only optical and electrostatic control, and can be performed at about 10 −10 mbar and at room temperature. We discuss the prospect of this method for coherently splitting the wavepacket of massive dielectric objects without using either projective measurements or an internal level structure.