QMath > Events > Quantum Lunch > Past Quantum Lunches
Past Quantum Lunches

14 December 2016, 12:0013:00
Quantum Lunch: Selftesting of quantum states: how to identify which state Alice and Bob share by letting them play a (nonlocal) game

7 December 2016, 12:0013:00
Quantum Lunch: Universality in interacting topological insulators

30 November 2016, 12:0013:00
Quantum Lunch: Instantaneous nonlocal quantum computation using the gardenhose model
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23 November 2016, 12:0013:00
Quantum Lunch: Semideviceindependent quantum randomness generation

16 November 2016, 12:0013:00
Quantum Lunch: MarchenkoPastur distributions and hypergeometric Hurwitz numbers

2 November 2016, 12:0013:00
Quantum Lunch: Nonabelian braiding by topological solitons

26 October 2016, 12:0013:00
Quantum Lunch: Quantum optics meets superconducting qubits

19 October 2016, 12:0013:00
Quantum Lunch: Informationtheoretic nonmalleability and authentication

12 October 2016, 12:0013:00
Quantum Lunch: Picking holes and cutting corners to achieve Clifford gates with the surface code

28 September 2016, 12:0013:00
Quantum Lunch: Periodically driven impurity in the XX quantum spin chain

21 September 2016, 12:0013:00
Quantum Lunch: Random tensor networks and multipartite entanglement

14 September 2016, 12:0013:00
Quantum Lunch: The martingale method meets the detectability lemma

7 September 2016, 12:0013:00
Quantum Lunch: Schrödinger Operators in Some Curvature Problems

31 August 2016, 12:0013:00
Quantum Lunch: Disentangling entangled quantum states

24 August 2016, 12:0013:00
Quantum Lunch: Autonomous feedback for superconducting qubits
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17 August 2016, 12:0013:00
Quantum Lunch:Tensor surgery and tensor rank
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10 August 2016, 12:0013:00
Quantum Lunch: An outsider's view on the mathematical foundations of machine learning

3 August 2016, 12:0013:00
Quantum Lunch: Analytic and (nearly) optimal selftesting bounds for the ClauserHoltShimonyHorne and Mermin inequalities

6 July 2016, 12:0013:00
Summer Quantum Lunch: Sandwiches and Sandwiched Renyi Divergences

29 June 2016, 12:0013:00
Quantum Lunch: Reality of TemperleyLieb Hamiltonian spectra

22 June 2016, 12:0013:00
Quantum Lunch: Quantum entropy derived from first principles

15 June 2016, 12:0013:00
Quantum Lunch: Quantum homomorphic encryption

8 June 2016, 12:0013:00
Quantum Lunch: Vote Talk

1 June 2016, 12:0013:00
Quantum Lunch: Introduction to fermionic observables

25 May 2016, 12:0013:00
Quantum Lunch: Scalar Field Theories with Polynomial Shift Symmetries

18 May 2016, 12:0013:00
Quantum Lunch: Landauer's principle and the energy cost of measurement

11 May 2016, 14:0015:00
After Quantum Lunch: Entropy power inequalities for qudits

11 May 2016, 12:0013:00
Quantum Lunch: Stahl's Theorem

4 May 2016, 12:0013:00
Quantum Lunch: Quantum gate learning in engineered qubit networks: Toffoli gate with alwayson interactions

27 April 2016, 12:0013:00
Quantum Lunch: Topological edge states are monogamous

20 April 2016, 12:0013:00
Quantum Lunch: Geometry of random planar maps with high degrees

13 April 2016, 12:0013:00
Quantum Lunch: Color Codes are cool

6 April 2016, 12:0013:00
Quantum Lunch: Describing nonMarkovian open quantum systems

30 March 2016, 12:0013:00
Quantum Lunch: Key Distillation

23 March 2016, 12:0013:00
Quantum Lunch: Dirac operators with magnetic link

16 March 2016, 12:0013:00
Quantum Lunch: Quantum manybody fluctuations around nonlinear Schrödinger dynamics

9 March 2016, 12:0013:00
Quantum Lunch: Towards experimentally feasible unbounded violation of quantum steering inequality

2 March 2016, 12:0013:00
Quantum Lunch: Tradeoff bounds for local error correction

24 February 2016, 12:0013:00
Quantum Lunch: Pattern formation in biological systems & Electroweak baryogenesis in 2HDMs

17 February 2016, 12:0013:00
Quantum Lunch: Deviceindependent twoparty cryptography secure against sequential attacks.

10 February 2016, 12:0013:00
Quantum Lunch: Trace inequalities for arbitrary many matrices via pinching

3 February 2016, 12:0013:00
Quantum Lunch: Tandem Talk

27 January 2016, 12:0013:00
Quantum Lunch: Gaussian optimizers in quantum information

20 January 2016, 12:0013:00
Quantum Lunch: Topological States in Graphene

13 January 2016, 12:0013:00
Quantum Lunch: A Pfaffian formula for monomerdimer partition functions

6 January 2016, 12:0013:00
Quantum Lunch: Determinism and causality. Which aspects are shared between classical physics and quantum physics?

16 December 2015, 12:0013:00
Quantum Lunch
Title: TBA
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9 December 2015, 12:0013:00
Quantum Lunch: Variational Expressions for Quantum Relative Entropies
Abstract: Distance measures between quantum states like the trace distance and the fidelity can naturally be defined by optimizing a classical distance measure over all measurement statistics that can be obtained from the respective quantum states. In contrast, Petz showed that...
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2 December 2015, 12:0013:00
Quantum Lunch
Title: Ktheory and topological insulators
Abstract: This will be an introductory seminar aimed at showing some basic facts in index theory and Ktheory in the context of topological insulators.
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25 November 2015, 12:0013:00
Quantum Lunch
Title: TBA
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18 November 2015, 12:0013:00
Quantum Lunch
Title: Errorcorrection in nonabelian anyon models
Abstract:
Scalable anyonic topological quantum computation requires the errorcorrection of nonabelian anyon systems. In contrast to abelian topological codes ...
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11 November 2015, 12:0013:00
Quantum Lunch
Title: On the Fermi Polaron in Two Dimensions
Abstract: We investigate the quantum system of a Fermi gas interacting
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attractively with a single impurity by contact interaction in a
twodimensional box. The contact interaction is implemented by a
limiting procedure ... 
4 November 2015, 12:0013:00
Quantum Lunch: Extensions of the entanglement entropy for symmetry protected topological order
Speaker: Shunji Matsuura
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28 October 2015, 12:0013:00
Quantum Lunch: Interaction Effects in SpinWave Theory
Speaker: Niels Benedikter
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21 October 2015, 12:0013:00
Quantum Lunch: Random permutations and the meanfield Heisenberg model
Speaker: Jakob Björnberg
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14 October 2015, 12:0013:00
Quantum Lunch: Renormalising entanglement distillation
Title: Renormalising entanglement distillation
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7 October 2015, 12:0013:00
Quantum Lunch: Entanglement Measures
Speaker: Roberto Ferrara
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30 September 2015, 12:0013:00
Quantum Lunch: Accurate atomic radii from ThomasFermi Theory
Speaker: Jan Philip Solovej
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23 September 2015, 12:0013:00
Quantum Lunch: Bogoliubov correction to the meanfield dynamics of interacting bosons
Speaker: Marcin Napiórkowski
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16 September 2015, 12:0013:00
Quantum Lunch: Quantum Circuits for Isometries
Speaker: Raban Iten
Abstract: Every quantum operation can be decomposed into a sequence of singlequbit and ControlledNot (CNOT) gates. In many experimental architectures, singlequbit gates are relatively ‘cheap’ to perform compared to CNOTs (for instance, being less susceptible to noise), and hence it is desirable to minimize the number of CNOT gates required to implement a circuit. I will consider the task of constructing an arbitrary isometry from m qubits to n qubits, while trying to minimize the number of CNOT gates required. I will show a lower bound and then give an explicit gate decomposition that gets within a factor of about two of this bound. Through Stinespring’s theorem this points to a CNOTefficient way to perform an arbitrary quantum operation.
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9 September 2015, 12:0013:00
Quantum Lunch
Title: Anyons in the averagefield approximation
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2 September 2015, 12:0013:00
Quantum Lunch: Nonbinding of strongly coupled manypolarons in dimensions two and three
Speaker: Anton Samojlow
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19 August 2015, 12:0013:00
Quantum Lunch: Estimates for the lowest eigenvalue of magnetic Laplacians.
Speaker: Fabian Portmann
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1 July 2015, 12:0013:00
Quantum Lunch: Localization from superselection rules in translation invariant systems
Abstract: We study a translation invariant spin model in a threedimensional regular lattice, called the cubic code model, in the presence of arbitrary extensive perturbations. Below a critical perturbation strength, we show that most states with finite energy are localized; the overwhelming majority of such states have energy concentrated around a finite number of defects, and remain so for a time that is nearexponential in the distance between the defects. This phenomenon is due to an emergent superselection rule and does not require any disorder. This is joint a joint work with Jeongwan haah.(1505.01480)
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24 June 2015, 12:0013:00
Quantum Lunch: Bogoliubov theory at positive temperature
Abstract: I will discuss Bogoliubov theory in the translation invariant case of a Bose gas. The theory arises by restriction to translation invariant quasifree states. I will introduce the positive temperature pressure functional and the corresponding ground state energy functional...
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17 June 2015, 12:0013:00
Quantum Lunch: Quantuminformation processing with solidstate singlephoton sources

10 June 2015, 12:0013:00
Quantum Lunch: The fractional Laplacian on bounded domains

3 June 2015, 12:0013:00
Quantum Lunch: Learning and testing of mixed state spectra
Abstract:An experiment produces an unknown mixed state, and you would like to learn some property of this state. How do you do this? The standard approach is to rerun the experiment multiple times and perform some measurement on the copies produced. The goal is then to learn or test the property using the smallest number of copies possible. In some cases, such as performing tomography on rank one pure states, researchers have designed algorithms which are optimal in their copy complexity. However, for many basic properties, including things as basic as estimating a mixed state's spectrum, this remains an open problem.In this talk, we consider learning and testing properties which depend only on the mixed state's spectrum. Natural problems in this space include learning its spectrum, estimating its von Neumann entropy, or testing whether it is low rank. Our results include (i) a new upper bound for learning a mixed state's spectrum and (ii) an optimal algorithm for testing whether a mixed state is equal to the maximally mixed state. We use techniques from the asymptotic theory of the symmetric group; in particular, we rely on Kerov's algebra of observables to help us study the moments of random Young diagrams.
Joint work with Ryan O'Donnell.» Read more 
20 May 2015, 12:0013:00
Quantum Lunch: Defining work from operational principles

13 May 2015, 12:0013:00
Quantum Lunch: An adaptive attack on Wiesner's quantum money
Abstract:
Unlike classical money, which is hard to forge for practical reasons (e.g. producing paper with a certain property), quantum money is attractive because its security might be based on the nocloning theorem. The first quantum money scheme was introduced by Wiesner circa 1970. Although more sophisticated quantum money schemes were proposed, Wiesner's scheme remained appealing because it is both conceptually clean and relatively easy to implement.We show efficient adaptive attacks on Wiesner's quantum money scheme (and its variant by Bennett et al.), when valid money is accepted and passed on, while invalid money is destroyed. We propose two attacks, the first is inspired by the ElitzurVaidman bomb testing problem, while the second is based on the idea of protective measurements. It allows us to break Wiesner's scheme with 4 possible states per qubit, and generalizations which use more than 4 states per qubit.» Read more 
6 May 2015, 12:0013:00
Quantum Lunch: an introduction to Hypercontractivity and LogSobolev inequalities, and their applications in Mathematical Physics and Quantum Information

29 April 2015, 12:0013:00
Quantum Lunch: Factorizable completely positive maps and Quantum Information Theory
Title: Factorizable completely positive maps and Quantum Information Theory
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22 April 2015, 12:0013:00
Quantum Lunch: Energy Levels of Dipoles in Graphene
Speaker: Simone Rademacher
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15 April 2015, 12:0013:00
Quantum Lunch
Title: TBA
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8 April 2015, 12:0013:00
Quantum Lunch
Title: A Classical Analog to Entanglement ReversibilityAbstract:In this letter we introduce the problem of secrecy reversibility. This asks when two honest parties can distill secret bits from some tripartite distribution pXYZ and transform secret bits back into pXYZ at equal rates using local operation and public communication (LOPC). This is the classical analog to the wellstudied problem of reversibly concentrating and diluting entanglement in a quantum state. We identify the structure of distributions possessing reversible secrecy when one of the honest parties holds a binary distribution, and it is possible that all reversible distributions have this form. These distributions are more general than what is obtained by simply constructing a classical analog to the family of quantum states known to have reversible entanglement. An indispensable tool used in our analysis is a conditional form of the G\'{a}csK\"{o}rner Common Information. 
25 March 2015, 12:0013:00
Quantum Lunch: Two results in topology, motivated by quantum computation
Speaker: Gorjan Alagic
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18 March 2015, 12:0013:00
Quantum Lunch
Title: TBA
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11 March 2015, 12:0013:00
Quantum Lunch: Heralded quantum gate with integrated error detection

4 March 2015, 12:0013:00
Quantum Lunch: Error distributions on large entangled states with nonMarkovian dynamics

25 February 2015, 12:0013:00
Quantum Lunch: A flea on Schrödinger's cat

18 February 2015, 12:0013:00
Quantum Lunch: Cryptography

11 February 2015, 12:0013:00
Quantum Lunch: Ground state entanglement constrains low energy excitations

4 February 2015, 12:0013:00
Quantum Lunch
Speaker: Niels Benedikter
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28 January 2015, 12:0013:00
Quantum Lunch
Speaker: Alexander MuellerHermes
Abstract: Quantum memories can be regarded as quantum channels that transmit information through time without moving it through space. Aiming at a reliable storage of information we may thus not only encode at the beginning and decode at the end, but also intervene during the transmission  a possibility not captured by the ordinary capacities....
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21 January 2015, 12:0013:00
Quantum Lunch
Speaker: Jeremy Sok
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14 January 2015, 12:0013:00
Quantum Lunch: Finding large gaps between tensor rank and border rank via algebras
Abstract: In quantum information theory, it is wellknown that the GHZstate 000+111 cannot be (SLOCC)transformed into the Wstate 000+101+011, but the Wstate can be approximated with states from the GHZorbit. The Wstate is thus an example of a tensor of tensor rank 3 that can be approximated by tensors of tensor rank 2....
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