Joint Seminar on Quantum Information and Technologies
2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | YouTube channel
until 2023/2024 Quantum Information Seminar | YouTube channel
2015-12-03 (Thursday)
room 1.02, Pasteura 5 at 10:30 
Frederic Grosshans (Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud)A Tight Lower Bound for the BB84-states Quantum-Position-Verification Protocol
We use the entanglement sampling techniques developed by Dupuis, Fawziand Wehner to find a lower bound on the entanglement needed by acoalition of cheater attacking the quantum position verificationprotocol using the four BB84 states in the scenario where the cheatershave no access to a quantum channel but share a (possibly mixed)entangled state Φ. For a protocol using n qubits, a necessary conditionfor cheating is that the max- relative entropy of entanglementEmax(Φ)≥n−O(logn). This improves previously known best lower boundby a factor ∼4, and it is essentially tight, since this protocol isvulnerable to a teleportation based attack using n−O(1) ebits ofentanglement.
2015-11-26 (Thursday)
room 1.02, Pasteura 5 at 10:30
Marcin Zwierz (IFT UW)Restoring quantum enhancement in the presence of realistic Gaussian dissipative environments
2015-11-19 (Thursday)
room 1.02, Pasteura 5 at 10:30
Mikołaj Lasota (Palacky University, Olomouc)Channel noise in discrete-variable quantum key distribution
2015-11-12 (Thursday)
room 1.02, Pasteura 5 at 10:30
Jan Chwedeńczuk (IFT UW)Squeezed states and beyond - production and properties
2015-11-05 (Thursday)
room 1.02, Pasteura 5 at 10:30
Rafał Demkowicz-Dobrzański (IFT UW)Convex optimization methods in quantum information - the magic of duality
2015-10-29 (Thursday)
room 1.02, Pasteura 5 at 10:30
Filip Kiałka (IFT UW)Spatial entanglement of nonvacuum states
2015-10-22 (Thursday)
room 1.02, Pasteura 5 at 10:30
Dardo Goyeneche (Uniwersytet Gdański)Five Measurement Bases Determine Pure Quantum States on Any Dimension
A long-standing problem in quantum mechanics is the minimum number of observables required for the characterization of unknown pure quantum states. The solution to this problem is especially important for the developing field of high-dimensional quantum information processing. We demonstrate that any pure d-dimensional state is unambiguously reconstructed by measuring five observables, that is, via projective measurements onto the states of five orthonormal bases. Thus, in our method the total number of different measurement outcomes (5d) scales linearly with d. The state reconstruction is robust against experimental errors and requires simple postprocessing, regardless of d. We experimentally demonstrate the feasibility of our scheme through the reconstruction of eight-dimensional quantum states, encoded in the momentum of single photons.
2015-10-15 (Thursday)
room 1.02, Pasteura 5 at 10:30
Konrad Banaszek (IFT UW)Restoring quantum enhancement in two-photon interferometry
2015-10-08 (Thursday)
room 1.02, Pasteura 5 at 10:30
Simon Benjamin (University of Oxford)Towards useful first generation quantum computers: a robust quantum 3-SAT solver
Various research teams, including the Martinis group in California and the Oxford-led UK Hub, have publicly set targets of creating quantum computers with hundreds of well-controlled qubits within a few years. Are such systems just demos of future, bigger systems, or are they big enough to be interesting as useful machines in their own right? I will argue that a key challenge for theorists is to understand how to perform useful tasks using imperfect operations on such '1st generation' hardware. I will describe a project that I'm working on to assess whether one can build a small quantum computer to solve 3-SAT, the famous and widely applicable problem in computer science. (This project is described in arXiv:1509.00667.)
2015-10-01 (Thursday)