Laser loop for engineering long-distance interactions in hybrid quantum systems

Light is a powerful carrier of quantum information and an established tool to manipulate matter at the quantum level.

In this action, we explore a novel technique of using light in quantum physics and technology: As a means to generate for the first time strong, quantum coherent interactions between different systems over macroscopic distances.

Our approach relies on a laser loop that connects the systems and mediates coherent bidirectional interactions between them.

This is possible due to a destructive interference of the quantum noise introduced by the light, otherwise responsible for decoherence. At the same time, information is erased from the output field, making the loop effectively closed to the environment.

This makes it possible to achieve quantum coherent coupling between the two systems.We will use this technique to couple a nanomechanical oscillator and an atomic spin ensemble in the quantum regime and we will engineer a variety of different interactions between them.

This enables the generation of state-swaps and two-mode squeezing, offering new possibilities for the quantum control of the motion of macroscopic objects.

Another particular focus will be understanding the role of the environment in quantum physics, which requires to induce dissipation in a controlled manner.

The laser loop scheme proposed in this action allows to engineer such an environment, and to profit from the large parameter tunability of atomic and nanomechanical devices to study the physics of non-Hermitian systems.

These feature degeneracies known as exceptional points, showing remarkable properties such as enhanced sensitivity to external parameters.

Exceptional points have mainly been investigated so far in a classical context and will be studied in this project in a hybrid quantum system.The research in this action will extend the toolbox for engineering long-distance interactions in quantum networks, also with relevance for quantum sensing and simulation.