Quantum technologies

Meeting ID: 517-538-4272
Passwort: 374880

Link: https://zoom.us/j/5175384272?pwd=RHVQckpRNjJ6T0JJd0M5SC9jSDRJQT09

Handouts and Slides

• fan_handout.pdf
• hess_handout.pdf
• fan_slides.pdf
• neureither_handout.pdf
• neureither_slides.pdf
• hess_slides.pdf
• arrufat_handout.pdf
• arrufat_slides.pdf
• derewjanko_handout.pdf
• gomez_handout.pdf
• derewjanko_slides.pdf
• gomez_slides
• weber_handout.pdf
• weber_slides.pdf
• barth_handout.pdf
• barth_slides.pptx
• lopez_handout.pdf
• lopez_slides.pdf

Presentation topics

1) Gate based quantum computing and the quantum circuit model (05.05.2020, Speaker: Daniel Fan, Supervisor: Martin Gärttner)

The standard model on which gate-based quantum computing is built is the quantum circuit model. This talk will give an introduction into the concepts of qubits and quantum gates and discuss the basics of quantum error correction.

Literature:

Nielsen and Chuang, Quantum Computation and Quantum Information, Cambridge University Press, in particular Chapters 4 and 10 (available at http://www-reynal.ensea.fr/docs/iq/QC10th.pdf)

IBM Quantum Experience user guide, https://quantum-computing.ibm.com/support/guides/user-guide?section=5dcb2b45330e880045abccb0

The Physical Implementation of Quantum Computation, DiVincenzo, David P. (2000-04-13)., Fortschritte der Physik. 48 (9–11): 771–783 (200), https://arxiv.org/abs/quant-ph/0002077

2) Quantum computing hardware (12.05.2020, Speaker: Konstantin Neureither, Supervisor: Philipp Preiss)

The most promising hardware implementations of qubits are superconducting circuits and trapped ions. But also many other physical systems such as quantum dots, topologically protected states, photons, nuclear spins, and ultracold atoms, in particular Rydberg atoms, are competing to become the first robust and scalable universal quantum computer. This presentation will introduce the working principles of some of these platforms and compare their strengths and weaknesses.

Literature:

Wikipedia: Quantum computing

The quantum technologies roadmap: a European community view, https://iopscience.iop.org/article/10.1088/1367-2630/aad1ea

Benchmarking an 11-qubit quantum computer, Wright, K., Beck, K.M., Debnath, S. et al., Nat Commun 10, 5464 (2019), https://arxiv.org/abs/1903.08181

High-Fidelity Control and Entanglement of Rydberg-Atom Qubits, Harry Levine, Alexander Keesling, Ahmed Omran, Hannes Bernien, Sylvain Schwartz, Alexander S. Zibrov, Manuel Endres, Markus Greiner, Vladan Vuletic, and Mikhail D. Lukin, Phys. Rev. Lett. 121, 123603 (2018), https://arxiv.org/abs/1908.06101

Superconducting qubits, IBM Q benchmark, https://www.ibm.com/blogs/research/2019/03/power-quantum-device/

3) Quantum supremacy: What does it actually mean? (19.05.2020, Speaker: Florian Hess, Supervisor: Martin Gärttner)

In October 2019 Google announced an experiment in which a quantum computer has solved a task in just a few minutes for which a classical computer would need years. We want to understand what their quantum computer actually did and how this is relevant in the context of complexity classes of problems that are hard to solve for classical computers and quantum computers, respectively.

Literature:

Quantum supremacy using a programmable superconducting processor, https://www.nature.com/articles/s41586-019-1666-5

Scott Aaronson’s Quantum supremacy FAQ: https://www.scottaaronson.com/blog/?p=4317

4) Adiabatic quantum computing (26.05.2020, , Speaker: Daniel Arrufat, Supervisor: Martin Gärttner)

A large class of optimization problems can be encoded as the ground state of a classical Ising model, or spin glass. Finding these ground states is a hard task for classical computer. Quantum annealers may solve this task efficiently by preparing the ground state adiabatically or by a process called annealing. In this session we want to understand the working principle and limitations of adiabatic quantum computation.

Literature:

Nature 473, 194–198 (12 May 2011), Quantum annealing with manufactured spins (more recent paper of the d-wave collaboration)

Science 294(5516), pp. 472-475 (2001) (https://arxiv.org/abs/quant-ph/0104129). (Original adiabatic quantum computing proposal)

American Journal of Physics 86, 360 (2018), Building an adiabatic quantum computer simulation in the classroom, Javier Rodríguez-Laguna, and Silvia N. Santalla

KITP lecture of Wolfgang Lechner: http://online.kitp.ucsb.edu/online/synquant-c16/lechner/ First ~15min are a very nice introduction to the topic.

5) Quantum simulation of the Fermi Hubbard model (02.06.2020, Speaker: Dennis Derewjanko, Supervisor: Philipp Preiss)

A major challenge in condensed matter physics is the understanding of high temperature superconductivity. The simplest model that is thought to reveal the relevant mechanisms is the Fermi-Hubbard model. Its experimental realization in a synthetic quantum system has been achieved using ultracold atoms trapped in optical lattices. We want to understand the working principle of this quantum simulation platform and the observed properties and their interpretation.

Literature:

Nature 545, 462-466 (2017), (https://arxiv.org/abs/1612.08436)

Revealing hidden antiferromagnetic correlations in doped Hubbard chains via string correlators Science 357, 484-487 (2017) (https://arxiv.org/abs/1702.00642)

6) Quantum simulation with Rydberg atoms (09.06.2020, Speaker: Jan Dreher, Supervisor: Philipp Preiss)

Trapped Rydberg atoms are a recently emerged promising platform for quantum simulation and computation. In such systems, individually controllable atoms are trapped optically and made to interact via laser-induced excitations to high-lying Rydberg states. Such interactions enable the simulation of spin models or the controlled creation of entangled states. Recent highlights in the field include the deterministic preparation of atomic arrays, observation of quantum dynamics, and generation of large-scale entangled states

Literature:

Probing many-body dynamics on a 51-atom quantum simulator, https://arxiv.org/abs/1707.04344

Generation and manipulation of Schrödinger cat states in Rydberg atom arrays, https://arxiv.org/abs/1905.05721

Many-body physics with individually controlled Rydberg atoms, Antoine Browaeys & Thierry Lahaye, Nature Physics 16, 132–142 (2020)

7) Digital quantum simulation of quantum electrodynamics (cancelled!, Speaker: Gioele Casagranda, Supervisor: Martin Gärttner)

The fundamental laws of physics are formulated as gauge theories. The equations governing the dynamics resulting from these models are notoriously hard to solve even numerically. Digital quantum simulators can be used to solve the discretized version of such models, as recently demonstrated in a trapped ion experiment. We want to understand the idea of digital quantum simulation and how the lattice Schwinger model can be simulated in this way.

Literature:

Nature 534, 516–519 (2016) (https://arxiv.org/abs/1605.04570) (Proof of principle experiment for using a digital quantum simulator to emulate lattice gauge theories.)

Science 334, 57 (2011) (https://arxiv.org/abs/1109.1512) (Demonstration of digital quantum simulation.)

8) Atomic Clocks: Boosting accuracy through entanglement (23.06.2020, Speaker: Santiago Gomez, Supervisor: Philipp Preiss)

Atomic clocks are amazingly sensitive time-keeping devices, reaching stabilities of 1:10¹⁹.  With today’s devices, it is possible to directly measure gravitational redshifts on the centimeter scale. Atomic clocks are the backbone of practical modern technology such as GPS, but also provide an experimental means to measure fundamental physics, such as possible time-dependence of fundamental constants.

This talk provides an introduction to the state of the art of atomic clocks and to possible future applications.  

Literature:

Optical atomic clocks, Andrew D. Ludlow, Martin M. Boyd, Jun Ye, E. Peik, and P. O. Schmidt, Rev. Mod. Phys. 87, 637 (https://arxiv.org/abs/1407.3493)

Optical Clocks and Relativity, C. W. Chou, D. B. Hume, T. Rosenband, D. J. Wineland, Science 329, 1630-1633 (2010) (https://arxiv.org/pdf/1803.01585.pdf)

Atomic Clocks for Geodesy, Tanja Mehlstäubler, Gesine Grosche, Christian Lisdat, Piet Schmidt, Heiner Denker, https://arxiv.org/abs/1803.01585

9) Squeezed light for quantum enhanced sensing (30.06.2020, Speaker: Sascha Weber, Supervisor: Philipp Preiss)

Quantum mechanics can be used to build measurement devices that are more sensitive than allowed by classical physics. To this end “squeezed” entangled states have to be engineered.  This technology is extremely useful wherever sensors are operated at their absolute minimum sensitivity, for example in atomic clocks or atomic fountains. We want to understand the general idea of using quantum states for sensing and discuss the use of squeezed light to enhance the sensitivity of the LIGO gravitational wave observatory

Literature:

Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of light, Ligo collaboration, Nature Photonics 7, 613–619(2013)

Quantum metrology with nonclassical states of atomic ensembles, Luca Pezzè, Augusto Smerzi, Markus K. Oberthaler, Roman Schmied, and Philipp Treutlein, Rev. Mod. Phys. 90, 035005 (2018).

Quantum sensing, C. L. Degen, F. Reinhard, and P. Cappellaro, Rev. Mod. Phys. 89, 035002  (2017), https://arxiv.org/abs/1611.02427

10) (Post) quantum cryptography. (07.07.2020, Speaker: Valentin Barth, Supervisor: Martin Gärttner)

Quantum technology will have a profound impact on the field of communication and cryptography. On the one hand, quantum key distribution (QKD) enables the sharing of encryption keys that are in principle completely secure against eavesdropping. An impressive example of this technology is the QKD distributions via satellite demonstrated in China. On the other hand, quantum computers have the potential to break current classical encryption schemes based on factorization (such as RSA), posing a serious threat for global data security. This calls for the development of “post-quantum” encryption protocols that are safe against attackers using a quantum computer.

This talk will review the principles of quantum key distribution (including BB84 protocol), discuss the current state of the art, and outline the rough ideas beyond post-quantum cryptography schemes.

Literature:

Satellite-to-ground quantum key distribution, Nature 549, 43–47(2017)

Post-quantum cryptography, Daniel J. Bernstein & Tanja Lange  Nature  549, 188–194(2017)

Practical challenges in quantum key distribution, Eleni Diamanti, Hoi-Kwong Lo, Bing Qi & Zhiliang Yuan npj Quantum Information 2, 16025 (2016)

Quantum cryptography, Nicolas Gisin, Grégoire Ribordy, Wolfgang Tittel, and Hugo Zbinden, Rev. Mod. Phys. 74, 145 (2002)

11) Quantum communication: The quantum internet (14.07.2020, Speaker: Álavaro Parra, Supervisor: Philipp Preiss)

One of the most advanced pillars of quantum technologies is the field of quantum communication. The working principles and challenges in building complex world-wide quantum communication networks are reviewed. Current efforts mainly focus on building a network of quantum repeaters for sharing entanglement. We want to understand the idea behind this protocol and review the state of the art in building large scale quantum networks.

Literature:

Quantum internet: A vision for the road ahead, https://pure.tudelft.nl/portal/files/47533107/qim_final_V7_FINAL.pdf

Quantum repeaters for communication, H.-J. Briegel, W. Dür, J. I. Cirac, P. Zoller, arXiv:quant-ph/9803056

The quantum internet, H. J. Kimble Nature 453, 1023–1030(2008) https://arxiv.org/abs/0806.4195

Übungsgruppen

• Gruppe A (Gärttner, Preiß)
  11 Teilnehmer/innen
  INF 227 / SR 2.404, Di 14:15 - 16:00