Quantum computing hardware: Trapped Ions
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 one of these platforms and compare their strengths and weaknesses.
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
Bruzewicz, C. D., Chiaverini, J., McConnell, R., & Sage, J. M. (2019). Trapped-ion quantum computing: Progress and challenges. Applied Physics Reviews, 6(2).
Quantum computing hardware: Rydberg-Atom Qubits
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 one of these platforms and compare their strengths and weaknesses.
The quantum technologies roadmap: a European community view, https://iopscience.iop.org/article/10.1088/1367-2630/aad1ea
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
https://arxiv.org/abs/1908.06101
Quantum computing hardware: Superconducting Qubits
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 one of these platforms and compare their strengths and weaknesses.
The quantum technologies roadmap: a European community view, https://iopscience.iop.org/article/10.1088/1367-2630/aad1ea
IBM Q benchmark
https://www.ibm.com/blogs/research/2019/03/power-quantum-device/
Krantz, P., Kjaergaard, M., Yan, F., Orlando, T. P., Gustavsson, S., & Oliver, W. D. (2019). A quantum engineer's guide to superconducting qubits. Applied physics reviews, 6(2).
Applications of near-term photonic quantum computers
Gaussian boson sampling (GBS) is a task that can be accomplished with near-term of photonic quantum systems. Recent advancements have resulted in the discovery of GBS algorithms that have applications in graph-based problems, point processes, and molecular vibronic spectra in chemistry. The development of dedicated quantum software and hardware plays a crucial role in enabling users to program devices and implement algorithms. This talk provides a review of the current state of the art in GBS algorithms and applications.
Bromley, T. R., Arrazola, J. M., Jahangiri, S., Izaac, J., Quesada, N., Gran, A. D., ... & Killoran, N. (2020). Applications of near-term photonic quantum computers: software and algorithms. Quantum Science and Technology, 5(3), 034010.
Demonstration of quantum supremacy on photonic processors
Gaussian boson sampling (GBS) is a task that can be accomplished with near-term of photonic quantum systems. Recent advancements have resulted in the discovery of GBS algorithms that have applications in graph-based problems, point processes, and molecular vibronic spectra in chemistry. This talk provides a review of the current state of the art in experimental demonstrations of the GBS task.
Madsen, L. S., Laudenbach, F., Askarani, M. F., Rortais, F., Vincent, T., Bulmer, J. F., ... & Lavoie, J. (2022). Quantum computational advantage with a programmable photonic processor. Nature, 606(7912), 75-81.
Quesada, N Conference presentation
https://www.youtube.com/watch?v=yfh8Y2zzPFA
Adiabatic quantum computing
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)
KITP lecture of Wolfgang Lechner: http://online.kitp.ucsb.edu/online/synquant-c16/lechner/ First ~15min are a very nice introduction to the topic.
Quantum supremacy: What does it actually mean?
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.
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
B Quantum Simulation
Classical computers quickly reach their limits when it comes to simulating complex quantum systems. Molecules or solids can only be simulated up to a size of around 50 atoms. This is due to the fact that the wave function of such a system contains countless components simultaneously, which a classical computer would have to process one after the other. In the 1980s, Richard Feynman proposed the idea of modeling the systems from individual atoms. This is because the particles naturally exhibit quantum parallelism. The first quantum simulators can be found in many laboratories and have already solved some problems faster than classical computers. The hope is to use more advanced quantum simulators to gain deeper insights into fundamental physics or to develop innovative materials, such as room-temperature superconductors and complex molecules.
Quantum simulation of the Fermi Hubbard model
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)
Quantum simulation with Rydberg atoms
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)
Digital quantum simulation of quantum electrodynamics
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.)
C Quantum Metrology and Sensing
Atomic Clocks: Boosting accuracy through entanglement
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.
Optical atomic clocks
Andrew D. Ludlow, Martin M. Boyd, Jun Ye, E. Peik, and P. O. Schmidt 87, 637 (https://arxiv.org/abs/1407.3493)
Optical Clocks and Relativity
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
Squeezed light for quantum enhanced sensing
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
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
Quantum sensing
https://arxiv.org/abs/1611.02427
Generation and application of NOON States
Quantum mechanics can be used to build measurement devices that are more sensitive than allowed by classical physics. To this end ”NOON” entangled states have been proposed. This technology is extremely useful wherever sensors are operated at their absolute minimum sensitivity. This talk will discuss how to generate NOON states and discuss their application potential.
High-NOON states by mixing quantum and classical light
Afek, I., Ambar, O., & Silberberg, Y. (2010).. Science, 328(5980), 879-881.
Quantum optical metrology–the lowdown on high-N00N states.Dowling, J. P. (2008).Contemporary physics, 49(2), 125-143.
Imaging and spectroscopy with undetected photons
Information plays a central role in quantum mechanics. Quantum interference, specifically, occurs when there is no available information to distinguish between superposed states. The presence of any information that could differentiate overlapping states prevents quantum interference. In this presentation, a quantum imaging concept will be discussed, which is based on induced coherence. This approach allows to obtain image information using photons to illuminate objects without the need for detection. Consequently, this application of quantum concepts allows the probe wavelength to be selected from a range where suitable detectors are not currently available, with potential applications in infrared spectroscopy.
Lemos, G. B., Borish, V., Cole, G. D., Ramelow, S., Lapkiewicz, R., & Zeilinger, A. (2014). Quantum imaging with undetected photons. Nature, 512(7515), 409-412.
Kviatkovsky, I., Chrzanowski, H. M., Avery, E. G., Bartolomaeus, H., & Ramelow, S. (2020). Microscopy with undetected photons in the mid-infrared. Science Advances, 6(42), eabd0264.
Gilaberte Basset, M., Setzpfandt, F., Steinlechner, F., Beckert, E., Pertsch, T., & Gräfe, M. (2019). Perspectives for applications of quantum imaging. Laser & Photonics Reviews, 13(10), 1900097.
Magnetometry with nitrogen-vacancy defects in diamond
Nitrogen-vacancy (NV) centers in diamond have received attention due to potential applications as nanoscale sensor for detecting weak magnetic fields. This naturally occurring defect has atomic-size and long spin-coherence times, making it ideal for NV magnetometry. This talk discusses the physical principles behind magnetic field detection with NV centres and key results towards applications.
Barry, J. F., Schloss, J. M., Bauch, E., Turner, M. J., Hart, C. A., Pham, L. M., & Walsworth, R. L. (2020). Sensitivity optimization for NV-diamond magnetometry. Reviews of Modern Physics, 92(1), 015004.
D Quantum Communication
Quantum-Secure Cryptography
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:
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) Post-quantum cryptography, Daniel J. Bernstein & Tanja Lange Nature 549, 188–194(2017)
Long-distance Quantum Communication with satellites
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.
Satellite-to-ground quantum key distribution, Nature 549, 43–47(2017) Satellite-based entanglement distribution over 1200 kilometers, Science 356, 1140-1144 (2017)
Long-distance Quantum communication: Quantum Repeaters
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.
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
