Strongly Correlated Quantum Walks in Optical Lattices (1409.3100v2)

Abstract: Full control over the dynamics of interacting, indistinguishable quantum particles is an important prerequisite for the experimental study of strongly correlated quantum matter and the implementation of high-fidelity quantum information processing. Here we demonstrate such control over the quantum walk - the quantum mechanical analogue of the classical random walk - in the strong interaction regime. Using interacting bosonic atoms in an optical lattice, we directly observe fundamental effects such as the emergence of correlations in two-particle quantum walks, as well as strongly correlated Bloch oscillations in tilted optical lattices. Our approach can be scaled to larger systems, greatly extending the class of problems accessible via quantum walks

• The paper demonstrates experimental control over ultracold bosonic atoms to initiate quantum walks that reveal distinct quantum correlations.
• It employs a digital micromirror device to prepare initial atomic states, enabling precise measurement of Hanbury Brown–Twiss interference effects.
• Key findings include the observation of fermionization and Bloch oscillations under strong interactions, underscoring advances in quantum simulation.

Strongly Correlated Quantum Walks in Optical Lattices

The paper "Strongly Correlated Quantum Walks in Optical Lattices" presents experimental advancements in the quantum simulation arena, focusing on the quantum walks of interacting bosonic atoms confined to optical lattices. The work demonstrates control over the dynamics of indistinguishable quantum particles in such a lattice, exploring the emergence of quantum correlations in two-particle systems and exploring strongly correlated phenomena like Bloch oscillations in tilted optical lattices.

The researchers implemented their paper using ultracold bosonic $^{87}$Rb atoms in optical lattice configurations, which allow detailed control over interaction strengths and tunneling rates. The cornerstone of their methodology is the precise control of initial atomic states via a digital micromirror device, allowing them to prepare distinct regions of atoms and initiate controlled quantum walks.

The haLLMark of this investigation is the measurement of quantum correlations stemming from Hanbury Brown-Twiss (HBT) interference during quantum walks of multiple indistinguishable particles. The paper elucidates how these walks differ from classical random walks due to quantum interference, which facilitates faster propagation and complex correlation structures.

The findings reveal that with weakly interacting bosons, there is clear evidence of quantum bunching attributed to HBT effects. As interaction strength increases, the bosonic system transitions into a strongly interacting regime akin to a Tonks-Girardeau gas, showcasing fermionization in one-dimensional setups. This fermionization is evidenced by anti-bunching behavior of bosons, observable as anti-diagonal peaks in the correlator maps, closely mimicking non-interacting fermionic behavior.

In addition to quantum walks of fermionized bosons, the paper explores the dynamics of repulsively bound pairs. These pairs emerge when bosons face strong on-site repulsive interactions; they effectively behave as single composite particles, showcasing coherent motion and executing Bloch oscillations with notable frequency doubling. This phenomenon was theoretically predicted but here empirically demonstrated under controlled experimental conditions.

The paper extends implications on both practical and theoretical levels. Practically, the methodologies and outcomes may enhance techniques in quantum information processing, particularly in utilizing quantum walks for solving complex computational problems. Theoretically, the paper adds depth to our understanding of strongly correlated quantum systems, laying groundwork for future investigations into many-body dynamics and disorder in quantum systems.

Looking forward, the scalability of these quantum walks in optical lattices presents significant potential. Further exploration might encompass the transition from few-body quantum dynamics to many-body scenarios, eventually leading to the realization and paper of more complex quantum phenomena such as quantum phase transitions and localization in disordered systems. These advancements could serve as a blueprint for developing robust quantum simulators capable of addressing numerous open questions in condensed matter physics and beyond.