We currently have four research projects in our group. In two experiments we explore quantum metrology with ensembles of ultracold atoms and atomic vapor cells. The other two experiments investigate quantum interfaces between atoms and solid-state nanosystems such as semiconductor quantum dots and nanomechanical oscillators. We closely collaborate with other research groups in Basel, at other Swiss universities and abroad. Our activities are integrated in the NCCR Quantum Science and Technology (QSIT) and the Swiss Nanoscience Institute (SNI) and receive funding from the European Research Council (ERC) and the Quantum Flagship.
Entanglement and quantum metrology on atom chips
Entanglement is a fundamental concept of quantum physics that still presents many conceptual challenges, in particular when applied to many-body systems of indistinguishable particles. At the same time, it is an essential resource for quantum technologies such as quantum metrology with atomic clocks and interferometers. In this project we use small atomic Bose-Einstein condensates on an atom chip – an exceptionally well-controlled quantum many-body system – to study many-particle entanglement and harness it for quantum metrology with chip-based interferometers.
Key results obtained so far include the creation of spin-squeezed states, a chip-based atom interferometer operating beyond the standard quantum limit, the observation of Bell correlations and Einstein-Podolsky-Rosen steering in a Bose-Einstein condensate.
Quantum memories for single photons
Semiconductor quantum dots are excellent single-photon sources, providing triggered single-photon emission at a high rate and with high spectral purity. Independently, atomic ensembles have emerged as one of the best quantum memories for single photons, providing high efficiency storage and long memory lifetimes. In this project, we aim at combining these systems for the first time, using a new type of quantum dot that emits photons at a wavelength compatible with Rubidium atoms, and a Rubidium quantum memory that is sufficiently broadband to accept these photons. The memory will be used to store and retrieve quantum dot single photons, realizing a quantum interface between these disparate physical systems. This will form the basis for experiments on hybrid entanglement and quantum networks.