Superconducting Quantum Devices SQUIDs, Qubits, and Quantum-Limited Amplifiers

summer term 2020
Lecturer: Priv.-Doz. Dr. Sebastian Kempf
Link zum LSF
30 participants

Important information related to coronavirus pandemic

Due to the present precautions against the further spread of the coronavirus the lecture as well as the tutorial will be held as an online course until further notice.

Technically, software offered by Zoom Video Communications will be used. The lecturer / tutor will sent around informations on how to connect to the lecture / tutorial to all lecture participants that have registred via the "Übungsgruppen-Portal".

During the lecture / tutorial, please switch off your camera and microphone and do not use a VPN connection to the university network in order to save traffic. Possiblities to ask questions during the lecture / tutorial will be discussed in the first lecture or tutorial, respectively.

Exam

The written exam is planned to take place on July 29th between 13:30 and 17:00 in the seminar rooms SR18, 19 and 20 in the building INF 306, first floor. The exam will start exactly at 14:15. The net time for working on the exam is 120min.

 

Before and after the exam a timeslot is foreseen to allow for entering / existing the seminar room without crowding.

 

Important: You have to explicitely register for the exam by writing an e-mail to the lecturer (see information provided in the "Materials" section)

 

More details will be announced soon.

Introduction

Superconducting quantum devices (SQDs) are electrical circuits utilizing the unique features of superconductivity such as dissipationless direct current flow, ideal diamagnetism, magnetic flux quantization and Cooper pair tunneling. SQDs can nowadays be reliablely fabricated using advanced thin-film technologies and allow building macroscopic systems such as artificial atoms that show quantum-mechanical behaviour. The scalability, reproducibility and controllability of these systems facilitate to study complex quantum-mechanical systems while having the unique possibility to adjust key system parameters such as coupling strengths, operation frequencies or energy scales. SQDs are therefore an outstanding experimental playground for investigating new physics under well-defined experimental boundary conditions. Besides this, SQDs are used as most sensitive devices for measuring or amplifying different physical quantities and are hotly tipped as very promising candidates for the implementation of a quantum computer.


This lecture gives a comprehensive introduction into the physics and applications of superconducting quantum devices. In particular, we discuss the physics of Josephson tunneling junctions which are of similar importance for SQDs than transistors for modern semiconductor circuits. We cover superconducting quantum interference devices (SQUIDs) that are presently the most sensitive wideband devices for measuring various physical quantities such as voltage, current or magnetic field that can be naturally converted into magnetic flux. We discuss different kinds of superconducting quantum bits and give an introduction into quantum computing using SQDs. Finally, we deal with SQD-based quantum-limited amplifiers that are presently the only devices overcoming existing noise limits of conventional semiconductor electronics.

Content

The lecture covers the following topics:
  • Introduction to superconductivity (perfect conductivity, ideal diagmagnetism, BCS theory, macroscopic wave function, magnetic flux quantization, Josephson effects)
  • Josephson tunnel junctions (realization of Josephson junctions, RCSJ-model, mechanical analogon, long and short Josephson junctions, behaviour in external magnetic fields, quantum-mechanical description of a Josephson junction)
  • Superconducting quantum interference devices (SQUIDs) (theoretical description of dc- and rf-SQUIDs, SQUID design, SQUID readout, SQUID applications)
  • SQUID based low-and high-frequency amplifiers
  • Microwave properties of superconductors, superconducting resonators
  • Superconducting Quantum Bits (Cooper pair box, flux qubit, phase qubit, transmon qubit, etc.)
  • Quantum-limited amplifiers, quantum measurements, quantum-mechanical description of amplifiers
  • Quantum computing, Deutsch and Shore algorithm, quantum error correction
  • Digital superconducting electronics

Prerequisite knowledge

Besides a general understanding of quantum mechanics and solid-state physics as gained by the module PEP5 , there is no prerequisite knowledge. All relevant aspects on superconductivity will be introduced within the lecture. Detailed knowledge about solid-state physics as gained by the advanced lecture on condensed matter physics (CMP) might be helpful.

Lecture organization

For the lecture, the following rules apply:
  • 6 credit points (6CPs) are available when passing the exam.
  • Each week, a problem set with one to three problems will be published. Solving these problem sets is optional but might be the best way for getting ready for the exam.
  • The problem sets are discussed within the plenary tutorial.
  • Registration for the plenary tutorial via webpage (mandatory!)

Practice groups

  • Group 1 (Dr. Mathias Wegner)
    30 participants
    INF 227 (KIP), SR 3.403 / 3.404, Wed 16:15 - 18:00
 
up
Superconducting Quantum Devices SQUIDs, Qubits, and Quantum-Limited Amplifiers
summer term 2020
Kempf
Link zum LSF
30 participants
calendar