Bragg Diffraction of Large Organic Molecules

Fast quantum interference of a nanoparticle via optical potential control

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 108 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.

Interferometric Mass Spectrometry

Accelerator mass spectrometry (AMS) is a widely used technique with multiple applications, including geology, molecular biology, and archeology. In order to achieve a high dynamic range, AMS requires tandem accelerators and large magnets, which thus confines it to big laboratories. Here we propose interferometric mass spectrometry (Interf-MS), a novel method of mass separation which uses quantum interference. Interf-MS employs the wave-like properties of the samples and as such is complementary to AMS, in which samples are particle-like. This complementarity has two significant consequences: (i) in Interf-MS separation is performed according to the absolute mass m, and not to the mass-to-charge ratio m/q, as in AMS; (ii) in Interf-MS the samples are in the low-velocity regime, in contrast to the high-velocity regime used in AMS. Potential applications of Interf-MS are compact devices for mobile applications, sensitive molecules that break at the acceleration stage and neutral samples which are difficult to ionize.

Polarization-spatial Gaussian entanglement in partially coherent light fields

The problem of bipartite entanglement in partially coherent paraxial vector light fields is addressed. A generalized uncertainty principle suited for the polarization-spatial degrees of freedom is introduced. Partial transpose is implemented through the obtained generalized uncertainty principle. Partial transpose is shown to be necessary and sufficient in detecting entanglement for a class of partially coherent vector light fields which have a spatial part to be Gaussian. An experimental realization of the studied entangled states using classical optical interferometry is outlined.

Kapitza-Dirac Blockade: A Universal Tool for the Deterministic Preparation of Non-Gaussian Oscillator States

Harmonic oscillators count among the most fundamental quantum systems with important applications in molecular physics, nanoparticle trapping, and quantum information processing. Their equidistant energy level spacing is often a desired feature, but at the same time a challenge if the goal is to deterministically populate specific eigenstates. Here, we show how interference in the transition amplitudes in a bichromatic laser field can suppress the sequential climbing of harmonic oscillator states (Kapitza-Dirac blockade) and achieve selective excitation of energy eigenstates, cat states, and other non-Gaussian states. This technique can transform the harmonic oscillator into a coherent two-level system or be used to build a large-momentum-transfer beam splitter for matter waves. To illustrate the universality of the concept, we discuss feasible experiments that cover many orders of magnitude in mass, from single electrons over large molecules to dielectric nanoparticles.