Seminar by Patrick Potts

We are happy to announce our next seminar.

Speaker: Patrick Potts (Lund University, SWE)
When: Thursday, 10th December 2020, 3PM (CET time)
Where: online (Zoom) zoom.us/my/aula.x

Title: Certifying nonclassical behavior for negative Keldysh
 quasiprobabilities


Abstract:
Quantum fluctuations behave fundamentally different from their classical counterparts. Due to the unavoidable measurement backaction in quantum mechanics, a measurement of multiple observables can in general not be described by a (positive) probability distribution that does not include the measurement apparatus explicitly. To describe fluctuations in the quantum regime without resorting to an explicit measurement apparatus, quasi-probability distributions which may become negative may be used. An example is provided by the Wigner function which generalizes the concept of phase space to quantum mechanics. Despite this difference between classical and quantum descriptions, it is a non-trivial task to decide if the fluctuations observed in an experiment arise from a classical or a quantum process. One reason for this is that measurement backaction, while avoidable in classical scenarios, may nevertheless be present. In this talk, I will show how one can rule out a classical description using an experimentally accessible inequality which is based on a few natural assumptions on the measurement apparatus. In quantum theory, this inequality can be violated if and only if a corresponding quasi-probabiliy distribution (called Keldysh quasi-probability distribution) becomes negative. Importantly, all assumptions on the detectors can be fulfilled in quantum theory, allowing for the conclusion that the measured data cannot be obtained from any classical process.


We are also glad to announce three more seminars
more details in the next weeks — SAVE THE DATE(S)

Speaker: Luca Razzoli (University of Modena & Reggio Emilia, ITA)
When: Thursday, 17th December 2020, 3PM (CET time)
Where: online (Zoom) zoom.us/my/aula.x
Title: Transport efficiency of continuous-time quantum walks on graphs

Speaker: Jan Chwedenczuk (Warsaw University, POL)
When: Thursday, 7th January 2020, 3PM (CET time)
Where: online (Zoom) zoom.us/my/aula.x
Title: Many-body nonlocality as a resource for quantum-enhanced
metrology

Speaker: Abolfazl Bayat (University of Electronic Science and Technology of China Chengdu, CHN)
When: Thursday, 14th January 2020, 3PM (CET time)
Where: online (Zoom) zoom.us/my/aula.x
Title: TBA