Overview of Lectures

     Quantum Computation and Quantum Error Correction                   

Hui-Khoon Ng    NUS, Singapore 3 hour class (2 lectures of 1.5 hours)

Lecture 1: Why quantum computation and where we are
I will give a broad overview of the subject of quantum computation, why people are excited about it, and the rapid push towards realising quantum computing devices.

Lecture 2: Quantum error correction - from the 3-qubit repetition code to surface codes
I will demonstrate the basic ideas of quantum error correction, the key approach to removing the effects of noise for accurate quantum computation, using the example of the 3-qubit repetition code. Even though the 3-qubit is very simple, it contains all the crucial features of quantum error correction that more powerful codes rely on. I will explain how one can go from the 3-qubit code to the very well-known surface codes, the current code of choice for quantum computing implementations and the basis of most of the recent experimental demonstrations of quantum error correction.

      Superconducting Quantum Circuits                                                   

Ioan Pop KIT, Karlsruhe, Germany   3 hour class (2 lectures of 1.5 hours)

Part 1: Introduction to Superconducting Quantum Circuits

• the Josephson junction
• superconducting qubits: Fluxonium and Transmon
• cQED and qubit readout
• Decoherence T1, T2

Part 2: The environment memory problem

• materials overview
• decoherence: Achille's heel
• Szilard quantum engine with superconducting qubits
• consequences for quantum error correction

Part 3: Lots of problems to solve, but are there roadblocks?

      Quantum Cryptography                                                                     

Ramona Wolf    University of Siegen, Germany 3 hour class (2 lectures of 1.5 hours)

Part I: Introduction to Quantum Key Distribution (QKD)

• Goal of QKD
• Quantum mechanical phenomena used in QKD
• General protocol structure

Part II: Security of Quantum Key Distribution

• Security definition
• Security proof structure
• Methods and challenges

Part III: Current topic: Composition of (quantum) communication protocols

• Example/Warning: How the composition of (quantum) communication protocols can compromise security
• What is needed to prevent these problems?
• Challenges for composing quantum with classical protocols

       Nanophotonics for quantum technologies                                      

Julien Claudon    UGA & CEA Grenoble (IRIG)   3 hour class (2 lectures of 1.5 hours)

Part I: Why and how to encode quantum information on light

• Light = an excellent carrier of information Classical (internet): light pulses, propagating over long distances in optical fibers
• Quantum technologies based on light
• Quantum description of light
• Two fundamentally distinct approaches: “Continuous variables” and “discrete variables” (reminiscent of wave-particle duality)
• Continuous variables:
• Discrete variables (main focus of the lecture)
• A single-photon as a qubit
• A key device: single-photon source. Requirements for an ideal single-photon source

Part II: Real-world single-photon sources

• Non-linear crystal (x^2)
• On-demand sources: Emission of a 2-level system; 1 electronic excitation (Pauli principle) -> 1 photon
• A gallery of solid-state artificial atoms
• A commercial single-photon source: Quandela
• Challenges
• Spontaneous emission in free-space
• The Purcell effect, cavity QED and waveguides

Part III: Open challenges: Single photons and beyond

• Long-haul Q-communications
• Photonic Q-computing
• Heterogeneous integration (III-V source, PIC: SiN platform, detectors: superconducting optical packaging is hard, but progresses)
• Communication between localized nodes: Spin-photon interfaces

    Quantum sensing: from discrete to continuous variables approaches     

Benjamin Pigeau   UGA & CNRS (Institut Néel, Grenoble) 3 hour class (2 lectures of 1.5 hours)

Introduction 

• Theory of measurement
• Signal to noise ratio
• Classical measurement backaction
• Quantum measurement backaction

Continuous variables 

• Probing with quantum fields
• The case of opto-mechanics
• The standard quantum limit
• How to beat SQL with Squeezing
• The case of Gravitational wave detectors

Discrete variables 

• Two level systems and qubits
• Coupling to external fields
• Qubits manipulation and readout
• The case of solid-state spin qubits

       Topological phases in atomic quantum simulators                            

Cécile Repellin   UGA & CNRS (LPMMC, Grenoble) 3 hour class (2 lectures of 1.5 hours)

I – A few essential concepts of topological physics
Berry phase
Chern number
A simple Chern insulator model

II – Cold atoms as quantum simulators of many-body physics
Optical lattices
Artificial gauge fields - the Harper-Hofstadter model
Bose-Hubbard and Fermi-Hubbard models

III – Fractional quantum Hall effect in ultracold atoms
The fractional quantum Hall effect, a short introduction
Quasi-adiabatic preparation
Measuring the many-body Chern number