One of the cornerstones of quantum communication is the unconditionally secure distribution of classical keys between remote parties by making use of the quantum properties of propagating electromagnetic waves. Now WMI researches demonstrate that continuous-variable quantum key distribution with propagating microwaves can be unconditionally secure with communication at room temperature up to distances of around 200 m. Most remarkable, they show that microwaves can potentially outperform conventional quantum key distribution at telecom wavelengths and imperfect weather conditions.
In an international collaboration with Japanese colleagues, WMI researchers developed a nonlinear Quantum Microwave Parametric Interferometer (QuMPI) based on superconducting quantum circuits. Interferometers are powerful tools for precision measurements in a plethora of research fields and applications. The accuracy of classical devices is bound by the standard quantum limit. However, this limit can be overcome by using quantum states or nonlinear quantum elements. WMI now succeeded to realize a nonlinear QuMPI. The fascinating properties of this device range from a signal-to-noise ratio exceeding the shot-noise limit to sub-Poissonian intensity fluctuations between its outputs. QuMPIs will promote applications ranging from quantum illumination to the search for axionic dark matter.
On 1 August 2023, Rudolf Gross becomes Scientific Director of the Munich Quantum Valley (MQV) and Managing Director of the Munich Quantum Valley e.V. association. He takes over the tasks from Rainer Blatt, who hands over the baton to him after about two years. Rudolf Gross has been closely associated with MQV from the very beginning: Together with Immanuel Bloch, Ignacio Cirac, Klaus Blaum and Raoul Klingner, he authored the strategy paper that led to the foundation of MQV. Since 2021, he is member of MQV and coordinates the Quantum Technology Park & Entrepreneurship (QTPE) consortium. He is also PI within the two MQV lighthouse projects NeQuS and IQ-Sense.
In an international collaboration, WMI researchers succeeded in the levitation of a superconducting lead-tin sphere with 100 μm diameter (corresponding to a mass of 5.6 μg) in a static magnetic trap with a resonance frequency of 240 Hz and quality facor above 107. The combination of low temperature, large mass, and high quality factor provides a promising platform for testing quantum physics in previously unexplored regimes with high mass and long coherence times.
In a panel discussion on "Quantum Technologies: Politics & Governance" moderated by Ulrich Mans (Quantum Delta NL) within the World of QUANTUM 2023, Petra Wolff (BMBF, Referat 514, QComputing/QTechnologies), Heike Riehl (IBM Research), Marianne Schoerling (GESDA, Open Quantum Institute), and Rudolf Gross (WMI, MCQST, MQV) discussed strategies and measures to promote quantum sciences and technologies in Europe. In particular, they addressed the questions what the EU’s position can be in the global quantum race and what type of European cooperation in QST is needed to achieve longterm technology leadership in Europe.
The extended 3rd edition of the textbook "Festkörperphysik: Aufgaben und Lösungen" by Gross, Marx, Einzel and Geprägs appeared at De Gruyter Oldenbourg. By providing full solutions, the exercise book with over 100 tasks and complete sample solutions allows students to both consolidate and expand their knowledge and to test what they have learned. The extended 3rd edition with many new exercises on topolgical quantum matter is ideally suited for exam preparation.
