December 2021
Abstracts of the QSIT/Quantum Center, ETH Zurich Lunch Seminar, Thursday, December 2, 2021
Parity measurement in the strong dispersive regime of circuit quantum acoustodynamics
Yu Yang – Hybrid Quantum Systems (Chu group), ETH Zurich
Mechanical resonators are emerging as an important new platform for quantum science and technologies. Proposals for using them to store, process, and transduce quantum information motivate the development of increasingly sophisticated techniques for controlling mechanical motion in the quantum regime. By interfacing mechanical resonators with superconducting circuits, circuit quantum acoustodynamics (cQAD) can make a variety of important tools available for manipulating and measuring motional quantum states. In this talk, I will show direct measurements of the phonon number distributions, parities, and Wigner functions of nonclassical mechanical states. We do this by operating our system in the strong dispersive regime, where a superconducting qubit can be used to spectroscopically resolve phonon Fock states. These measurements are some of the basic building blocks for constructing more complex devices such as acoustic quantum memories and processors.
Challenges for Practical Device-Independent Quantum Key Distribution
Ramona Wolf - Quantum Information Theory (Renner group), ETH Zurich
Quantum key distribution (QKD) promises unconditional security in data communication based on the principles of quantum mechanics. Device-independent QKD, in addition, allows for this level of security while relaxing the assumptions that are made; it does not rely on any assumptions on the quantum devices used in the protocol. In this way, an attacker cannot exploit deviations of the real devices from their theoretic idealization to obtain information about the messages sent.
The improved security guarantee naturally comes at a cost: The fact that we make (almost) no assumptions about the devices brings new challenges for both the theoretical analysis and the experimental realization. In this talk, I will discuss problems that arise when making the transition from theoretical ideas to experimental implementations of device-independent QKD protocols and comment on recent experimental progress.