Self-Interference of a Matter Wave: Loss of Fringes Not Knowing Which Way

Uwe Becker

Sergei Studenikin, Yousef Karimi Yonjali, Alex Bogan +2 more

A single sound quantum emitted from two places interferes with itself, like a particle passing through two slits. The fringe position reveals whether the sources emit with the same sign (symmetric) or opposite signs (antisymmetric). Knowing this symmetry is important because qubits in solids lose energy by emitting such sound quanta, phonons. For a qubit shared between two sites, antisymmetric emission cancels at long wavelengths, suppressing energy loss, whereas symmetric emission does not. Lifetime measurements give only the total loss and cannot distinguish them. Such fringes appear in double quantum dots, but their position has not been analysed. Here we measure it for single phonons emitted as one hole tunnels between two gallium arsenide quantum dots. Using a quantitative model of sound focusing in the crystal, we find that the two dots emit antisymmetrically, as expected for a moving charge, with only a small symmetric part. Spin-flip transitions in a magnetic field weaken the fringes without shifting them. For double-dot charge qubits, antisymmetric emission is predicted to reduce phonon losses strongly at the frequencies where qubits operate, and phonon interferometry gives a direct way to measure how qubits release energy and to design longer-lived qubits.

Sourav Kesharee Sahoo, Ashutosh Dash, Radhika Vathsan +1 more

The Schr\"odinger-Newton equation has frequently been studied as a nonlinear modification of the Schr\"odinger equation incorporating gravitational self-interaction. However, there is no evidence yet as to whether nature actually behaves this way. This work investigates a possible way to experimentally test gravitational self-interaction. The effect of self-gravity on the interference of massive particles is studied by numerically solving the Schr\"odinger-Newton equation for a particle passing through a double-slit. The results show that the presence of gravitational self-interaction has an effect on the fringe width of the interference that can be tested in matter-wave interferometry experiments. Notably, this approach can distinguish between gravitational self-interaction and environment-induced decoherence, as the latter does not affect the fringe width. This result will also provide a way to test if gravity requires to be quantized on the scale of ordinary quantum mechanics.

Arbab I. Arbab

David O Hayward

Jonas Rodewald, Philipp Haslinger, Nadine Dörre +4 more

We present matter-wave interferometry as a tool to advance spectroscopy for a wide class of nanoparticles, clusters and molecules. The high sensitivity of de Broglie interference fringes to external perturbations enables measurements in the limit of an individual particle absorbing only a single photon on average, or even no photon at all. The method allows one to extract structural and electronic information from the loss of the interference contrast. It is minimally invasive and works even for dilute ensembles.