Physics Colloquium
 Speaker Dr Saleh Rahimi-Keshari Affiliation School of Physics, IPM Title of talk Nonclassical Resources for Quantum-Computational Supremacy ??????: ????? ????????? ???? ????? ??????? ??????? Date and time Wednesday, 6 Mehr 1401 (28th of Sept. 2022), 6-7:30 pm Link for online seminar Abstract It is believed that quantum computers can perform certain computational tasks much more quickly than their classical counterparts, a milestone known as quantum-computaional supremacy. A universal fault-tolerant quantum computer, however, is still not available, so there is keen interest in intermediate models of quantum computation, which can demonstrate quantum-computational supremacy with simpler physical systems and algorithms. A class of these intermediate models consists of sampling problems, i.e., generating samples from the output probability distribution of a quantum circuit that is believed to be hard to simulate efficiently classically. In this talk, I will show that the negativity in phase-space quasiprobability distributions is an essential nonclassical resource for quantum-sampling problems not to be efficiently simulatable by using classical computers. Then by considering boson-sampling experiments, which use single-photon or squeezed-light sources and on-off detectors, I will discuss that errors and imperfections can have deleterious effects on the negativity, and above some threshold of errors, these experiments become classically simulatable. In addition, I will briefly talk about the role of the negativity as a nonclassical resource in nonequilibrium quantum thermometry and device-independent quantum cryptography.  
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