Multi-Scale Cluster Interference (MUSCLE)

The wave-particle duality of matter belongs to the most fundamental features of quantum physics. It illustrates the conceptual contradiction between a continuous, wave-like evolution of probability amplitudes and the particle-like reduction to well-defined positions during a measurement.

The quantum wave nature of matter has been visualized in many experiments before for electrons, neutrons, atoms and even molecules. It has, however, remained an open question how non-local quantum superpositions merge into the local phenomena that we are used to see around us, every day. An unbiased way of approaching this question is to systematically increase the mass and size of objects in advanced quantum experiments.

The Vienna QNP group holds the current mass world record in matter-wave interferometry and here proposes to increase this by another order of magnitude. While previous high-mass interference experiments were performed with organic materials with limited abundance and thermal stability, we here propose to establish experiments with large metal clusters that may even have a mass-velocity product of 2 10^7 amu × m/s. This allows for 60 m/s fast objects with a mass of around 300 kDa.

Metal clusters have never been employed in de Broglie studies before and their low work function will enable the use of three continuous photodepletion gratings. A scalable cold cluster source shall fulfill the demanding requirements for high-mass experiments in the \(10^4 -10^6\) amu range.

An intense beam of cluster anions will be generated by collisional aggregation in a cold noble gas vapor. The ions will be mass selected in a quadrupole mass filter, internally and translationally cooled in a cryogenic ion guide and then neutralized by ultraviolet electron detachment in ultra-high vacuum.

The low work function of metals is the key to realizing three continuous photodepletion gratings with a standing wave period of 133 nm and it will facilitate single-photon ionization mass spectrometry detection. 

The MUlti-Scale CLuster Interference Experiment (MUSCLE) will provide charged and neutral clusters with a wide atom number distribution from a few to beyond 10’000 atoms per particle. The cryogenic setting will allow to prepare structurally simple cold nanoparticles and effectively suppress thermal quantum decoherence.

MUSCLE will push the experimental limits in the search for nonstandard quantum phenomena that are all predicted to scale with the square of the particle mass.

MUSCLE will also define a new mile stone in matter wave physics because it opens a door to quantum experiments with a new material class, effectively comprising third of the entire periodic table, from alkaline over alkaline earth clusters, rare earth and coinage metals but also decorated and mixed nanoparticles. MUSCLE will render their size and conformation-dependent electronic and magnetic properties accessible to quantum-assisted measurements.