Coherence in the presence of absorption and heating in a molecule interferometer

Abstract

Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential.

Quantum‐Assisted Metrology of Neutral Vitamins in the Gas Phase

“…A molecule may also absorb a photon in transit through the diffracting laser field. This is an additional matter‐wave beam splitting mechanism, which also modulates the fringe visibility 10. A correct interpretation of the V ( P ) curve (Figure 3) thus hinges on good knowledge of the laser intensity in G2, which we have calibrated in situ by using C 60 molecules 16…”

Multiphoton absorption in optical gratings for matter waves

“…This difference was not observed in previous experiments [26,32] because it only shows up in interference patterns recorded with a sufficiently narrow velocity distribution. Recent experiments with improved velocity selection [9] reveal the model discrepancy and provide evidence for the present quantum model.…”

“…when a coherent plane matter wave hits the grating. The phase modulation (2)- (4) leads to diffraction peaks separated by the grating momentum 2 k L [9],…”

“…Specifically, the theory developed below is required to quantitatively describe a recent experiment with C 70 fullerenes which featured a high laser power and unprecedented velocity resolution [9]. It provides evidence that the momentum recoil upon photon absorption from a standing light field is coherent in the sense that it leads to a superposition of the momentum kicks associated with the two possible photon directions, rather than to a mixture.…”

“…Motivated by experiments [3][4][5][6][7][8][9] that use a standing light field as diffraction element, we focus on the interaction between a standing-wave laser grating and a delocalized and internally complex molecule. It has been seen earlier that spontaneous emission, light scattering, or thermal radiation induced by an optical grating can lead to decoherence [10][11][12].…”