Department > Lectures > Winter term 2018/2019 > Superconducting Quantum Devices: SQUIDs, QuBits, and Quantum-Limited Amplifiers

Superconducting Quantum Devices: SQUIDs, QuBits, and Quantum-Limited Amplifiers

winter term 2018/2019
Lecturer: Priv.-Doz. Dr. Sebastian Kempf
Link to LSF
22 participants

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 boundary conditions. Besides this, SQDs are used as the 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, there is no prerequisite knowledge. All relevant aspects on superconductivity will be introduced within the lecture. Basic knowledge about solid-state physics as gained by the introduction into solid-state physics (PEP5) or the advanced lecture on condensed matter physics (CMP) are helpful.

Exam

Post-exam review: February 20th, 2019, 14:00-15:00 (KIP SR 2.404).

Please bring a student ID-card or photo ID. In case you want to review a colleague's exam you have to present a written authorization.

 

The exam will take place on February 6th, 2019, 14:00-16:00 (Phil.-Weg. 12 nHS).

Organization

  • 6 Credit points (6CPs) are available when passing the exam.
  • Participation in the exam will be possible when reaching at least 50% of the available points of the problem sets.
  • Registration for the plenary tutorial via webpage (mandatory!)
  • 10 points per problem set, 12 problem sets in total

Tutorials

  • Group 1 (Anna Ferring)
    22 participants
    INF 227 / SR 1.404, Wed 14:15 - 15:00
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Superconducting Quantum Devices: SQUIDs, QuBits, and Quantum-Limited Amplifiers
winter term 2018/2019
Kempf
Link zum LSF
22 participants
calendar