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  • Event
    Modular Hamiltonians and relative entropy
    25.03.2025
    To obtain finite results, one needs to consider measures such as relative entropy, which can be computed from the modular Hamiltonian using Tomita--Takesaki theory. In this talk, I will explain the connection between the quantum-mechanical expressions for (relative) entropy, the modular Hamiltonian and Tomita--Takesaki theory. I then present two examples of modular Hamiltonians that were recently derived: one for conformal fields in diamond regions of conformally flat ...
  • News
    "Quantentechnologie: Sind wir erst am Anfang?"
    13.06.2019
    "Quantentechnologie: Sind wir erst am Anfang?". The event is part of the series "Nachgefragt" organised by the University of Vienna, that brings together science, journalism and the public to discuss topics that are relevant for society. How do quantum computers and quantum communication work? And how will they change our daily lives in the future? Markus Aspelmeyer answers the questions of the audience and of the science journalist Thomas Kramar (Die Presse) on the future ...
  • News
    Invitation to talks by: Pepijn W.H. Pinkse, Claudio Conti and Giulia Marucci, Tuesday Feb. 20th 2018, 2:00 PM at the IQOQI Seminar Room
    20.02.2018
    (CRAB). Optical quantum solitons are the quantum counterpart of the self-localized propagation-invariant optical classical solitons. Surprisingly, the evolution in the quantum regime is characterized by spreading. We control quantum solitons by computing an optimal time-dependent perturbation to the Hamiltonian, achievable by dispersion or nonlinearity management in an optical fiber. By combining stochastic partial differential equations and CRAB, we look for the optimal ...
  • Event
    Entangling microwaves and optics
    20.01.2025
    Moreover, hybrid entanglement between localized systems and itinerant photons has extended these applications to distributed quantum computing and sensing. Thus far, such hybrid entanglement has remained divided into two paradigms - microwave photons entangled with microwave-based quantum devices such as superconducting qubits, and optical photons entangled with optically-addressable systems such as atoms. Uniting these two paradigms will enable new capabilities in hybrid ...
  • News
    Invitation to a talk: Barbara Lopes Amaral, Monday, May 14th 2018, 14:00 at the IQOQI Seminar Room
    14.05.2018
    Contextuality is a fundamental feature of quantum theory necessary for certain models of quantum computation and communication. Serious steps have therefore been taken towards a formal framework for contextuality as an operational resource. However, the main ingredient of a resource theory - a concrete, explicit form of free operations of contextuality– was still missing. Here we provide such a component by introducing noncontextual wirings: a class of contextuality-free ...
  • Event
    Solving Quantum Max Cut via Swap Operators
    23.10.2024
    generated by the swap operators. We find that level-2 of this new hierarchy is exact (up to tolerance 10^−7) on all QMC instances with uniform edge weights on small graphs. The second contribution of this talk is a polynomial-time algorithm that exactly computes the maximum eigenvalue of the QMC Hamiltonian for certain graphs, including graphs that can be ``decomposed'' as a signed combination of cliques. A special case of the latter are complete bipartite graphs with ...
  • News
    Model for optimizing quantum key distribution with continuous-wave pumped entangled-photon sources
    19.08.2021
    Quantum key distribution (QKD) allows unconditionally secure communication based on the laws of quantum mechanics rather than assumptions about computational hardness. Optimizing the operation parameters of a given QKD implementation is indispensable in order to achieve high secure key rates. So far, there exists no model that accurately describes entanglement-based QKD with continuous-wave pump lasers. We analyze the underlying mechanisms for QKD with temporally uniform ...
  • Event
    Suppressing Noise due to Dissipation in a Variational Quantum Eigensolver
    16.01.2024
    The accuracy of VQEs reduces in the presence of quantum noise, thus affecting the quantum state preparation. A dominant type of noise, that superconducting quantum computers have, is amplitude damping. In this thesis, we investigate a penalized VQE and a symmetry-based method to mitigate the effects of amplitude damping noise in VQEs. We consider the cluster-Ising model and the surface-code model as the problem Hamiltonians. We determine optimal hyper-parameters of the ...
  • News
    Job Announcements of our Strategic Partner - International Center for Theory of Quantum Technologies
    19.09.2018
    https://euraxess.ec.europa.eu/jobs/336975 [2] 3. Call for applications for Group Leader for the research group Quantum Open Systems - https://euraxess.ec.europa.eu/jobs/336981 [3] 4. Call for applications for Group Leader for the research group Quantum Computation, Quantum Error Correction and Many-body Systems - https://euraxess.ec.europa.eu/jobs/336990 [4] 5. Call for applications for Post-doctoral Researchers for the research group Multiphoton Quantum Optics for Quantum ...
  • News
    Towards complete control of multi-level quantum systems
    07.11.2017
    so-called quarter and half wave plates. The latest research on quantum gates in higher-dimensions is an analogue of these two elements for the OAM of light and in higher dimensions. The idea how to construct such basic elements was originally found by a computer algorithm called Melvin, which has been developed by the Viennese group two years ago. Based on this idea, the scientists were able to show the experimental implementation of all basic elements, necessary for a ...