The research interests of the group of Jörg Schmiedmayer (JS) concentrate on understanding quantum science and developing from there a robust quantum technology. Experimental investigations span a wide range from fundamental questions of many body quantum physics to the development of components for a quantum repeater or applications of quantum systems for sensing and metrology.
Many of the components of a quantum toolbox were developed in atomic physics and quantum optics, where the advantage of atomic systems stems from their extreme precision, reproducibility (each atom is identical), and the high degree of quantum coherence that can be achieved. It is interesting to note, that only a few specific properties (like spin) are needed to execute a quantum function. By special engineering a molecular scale device and its host it should be possible to protect these properties and achieve high fidelity quantum functions.
The research projects connected to Solids4Fun centre around the questions: (1) Can one design and implement systems in a solid-state environment that can perform the quantum functions usually associated with atoms? (2) Can one transfer the powerful techniques emerging from Quantum Information Science and Atomic Physics/Quantum Optics to such solid-state based systems, how to connect, interface and integrate them? Research in Solids4Fun will concentrate on developing such molecular scale systems and to quantum interconnect them to photons. Detailed protocols exist for linking photonic quantum states with atoms. The JS group starts from its experience with implementing a quantum link between photons and quantum states stored in ensembles of atoms and extend it towards solid state embedded or surface mounted quantum devices.
One of the most promising solid state embedded quantum system, and one that operates as a quantum system at ambient temperatures, are optically active defect centers in diamond, the best investigated is the nitrogen-vacancy (NV) centre, and there are many others. It is planned to research and exploit their quantum properties. Placing them in an optical micro-cavity will drastically enhance the coupling to selected photon modes. This will allow us to implement a robust and applicable quantum toolbox that can be used in many applications ranging from ultra precise sensing to quantum communication and simulation. One interesting example of a quantum function is magnetic field sensing: Models of a quantum limited NV sensor predict a sensitivity of < 3 nT/Hz1/2. This would allow build a nano-scale magnetometer (for recent progress see, that can detect a single nuclear spin at a distance of 10 nm, and function in a biological setting.
A new direction that will be opened up by collaboration within Solids4Fun is the possibility to design molecular scale devices especially for function and for the environment they are put in. Ideally these designed molecular scale devices should be able to ‘live’ in a magnetically quiet environment, the nuclear spin content of the environment needs to be controlled and well defined. Diamond, which can be 13C depleted, is a good candidate, similarly 28Si or a superfluid 4He film. If these molecular scale systems have a large electric dipole moment (dipolar molecule) or have a large magnetic moment (molecular magnet) they would be ideal candidates for designed functionalized quantum matter for connecting to the superconducting circuits as envisioned by Johannes Majer, or to build novel quantum simulators for strongly correlated dipolar systems.
A different issue to consider when designing embedded molecular scale devices is inhomogeneous broadening. In any realistic setting the local environment on a surface or in a solid is different at each location, and leads to significant shifts of the energy of the quantum states. This can be either a resource, or a nuisance. If the coupling to the molecular scale device is very strong, then it allows addressing each ‘system’ individually. If one works with ensembles, then selecting homogeneous subensembles with designed spectra will be essential.