# Symmetric Bloch oscillations of matter waves

## TL;DR

This paper demonstrates symmetric Bloch oscillations of matter waves in two accelerated optical lattices, enabling large coherent momentum splittings and potential applications in fundamental physics tests.

## Contribution

It introduces a novel extension of Bloch oscillations to two superposed lattices, enabling coherent splitting and recombination of matter waves with large momentum transfer.

## Key findings

- Achieved up to 240ħk momentum splitting in cold Cesium atoms.
- Mapped the energy band structure using momentum parity-symmetry.
- Demonstrated coherent matter wave interferometry with symmetric Bloch oscillations.

## Abstract

Cold atoms in an optical lattice provide an ideal platform for studying Bloch oscillations. Here, we extend Bloch oscillations to two superposed optical lattices that are accelerated away from one another, and for the first time show that these symmetric Bloch oscillations can split, reflect and recombine matter waves coherently. Using the momentum parity-symmetry of the Hamiltonian, we map out the energy band structure of the process and show that superpositions of momentum states are created by adiabatically following the ground state of the Hamiltonian. The relative phase and velocity of the two lattices completely determines the trajectories of different branches of the matter wave. Experimentally, we demonstrate symmetric Bloch oscillations using cold Cesium atoms where we form interferometers with up to $240\hbar k$ momentum splitting, one of the largest coherent momentum splittings achieved to date. This work has applications in macroscopic tests of quantum mechanics, measurements of fundamental constants, and searches for new physics.