# The 25th Workshop on Nanoscale and Mesoscopic Systems

From Mesoscopics

"Exotic Quantum States in Circuit QED Systems"

- Nov 1--2, 2012
- Hogil Kim Memorial Building Room 512, POSTECH, Pohang, Korea

Recently, there have been strong activities in the field of quantum states of circuit QED system. Supposedly, the circuit QED system is one of the two most promising candidates for the solid-state based quantum information processing -- the other is the diamond NV center. At this workshop we will see why.

This workshop is supported by the APCTP.

## Invited Speakers

- Ashhab, Sahel (RIKEN, Japan)
- Johansson, Robert (RIKEN, Japan)
- Nation, Paul D. (Korea Univ, Korea)
- Schmidt, Sebastian (ETH Zurich, Switzerland)
- Semba, Kouichi (National Institute of Informatics, Japan)

## Program

**Time Table**

**Thu Nov 1****12:00 - 12:50**Registration**13:00 - 14:15**Nation**14:30 - 15:45**Semba 1**15:45 - 16:00**Coffee**16:00 - 17:15**Johansson 1**17:30 - 18:45**Schmidt 1**19:00 - 21:00**Banquet (free of charge)

**Fri Nov 2****09:15 - 10:30**Ashhab 1**10:45 - 12:00**Schmidt 2**12:00 - 13:00**Lunch**13:00 - 14:15**Semba 2**14:30 - 15:45**Ashhab 2**15:45 - 16:00**Coffee**16:00 - 17:15**Johansson 2

**Nation, Paul D. (Korea Univ)**- The Superconducting Circuit Warm Up
- Why superconducting circuits?
- The quantized LC-oscillator.
- The need for nonlinearities.
- The Josephson effect.
- The JJ as a lumped inductor.
- Qubits: Charge, Flux, and Phase.
- The dc-SQUID as a flux tunable inductor.
- Coupling HO’s and Qubits: The Jaynes-Cumming model and nonlinearities.
- Controlling the state of a HO with a qubit.
- Strong coupling in circuit-QED.
- Hybrid quantum systems with circuit-QED elements.
- Recent experiments with circuit-QED

- The Superconducting Circuit Warm Up

**Ashhab, Sahel (RIKEN, Japan)**- Cavity QED in the ultrastrong-coupling regime
- Why do we study cavity QED in the ultrastrong coupling regime?
- What theoretical tools and approximations can we use?
- What interesting properties does this system have?
- How can these interesting properties be observed in experiment?

- A few ideas and experiments on preparing interesting states in a superconducting resonator coupled to a qubit
- Extracting a Schrödinger-cat state in a cavity from a qubit- resonator entangled state.
- Preparing Schrödinger-cat states with the help of dispersive frequency shifts (implemented recently by Yale group).
- Preparing an arbitrary cavity state using the Law-Eberly protocol (implemented by Hofheinz et al., UCSB).
- State manipulation via measurement (with some paradoxes).

- Single-artificial-atom using a voltage-biased superconducting charge qubit
- System and a rough description of lasing mechanism.
- Simplified two-level model
- Realistic three-level model

- Using superconducting qubit circuits for quantum simulation

- Cavity QED in the ultrastrong-coupling regime

**Johansson, Robert (RIKEN, Japan)**- Dynamical Casimir effect in superconducting circuits
- Frequency-tunable microwave resonators
- Vacuum amplification and nonadiabatic photon creation
- Dynamical Casimir effect in superconducting circuits
- Review of experiments

- QuTiP: Quantum Toolbox in Python with case studies in Circuit-QED
- Introduction to QuTiP
- Open quantum system simulations with master equations and Monte-Carlo methods
- Case studies: numerical simulations of circuit-QED systems
- Jaynes-Cummings-like models
- Qubit gates
- The Dicke model
- Parametric amplifier
- Correlation functions and nonclassicality tests

- Dynamical Casimir effect in superconducting circuits

**Schmidt, Sebastian (ETZ Zurich, Switzerland)**- Single Cavity Physics (Lecture Note)
- Jaynes-Cummings model
- Photon blockade under coherent excitation
- Photon blockade under incoherent excitation
- Comparison to Coulomb blockade

- Two-coupled cavity systems (Lecture Note)
- Unconventional Photon blockade due to quantum interference
- Self-trapping of photons

- Large arrays: The Jaynes Cummings Hubbard model (Lecture Note)
- Quasi-equilibrium: Superfluid-Mott insulator transition
- Quench Dynamics
- Non-equilibrium steady states

- Single Cavity Physics (Lecture Note)

**Semba, Kouichi (National Institute of Informatics, Japan)**- Superconductivity and Josephson circuit QED
- Essence of superconductivity revisited
- Spontaneous symmetry breaking
- Nambu-Goldstone mode & Anderson-Higgs Mechanism
- Josephson quantum circuit as an artificial atom : qubit
- Cavity-QED : From atomic system to Josephson circuit

- Hybrid Quantum Systems
- Superconducting qubit as a macroscopic quantum system
- Merit of coupling to the atomic system
- Appealing NV-diamond, not just by its color
- How to prepare NV centers and the strong coupling ?
- Exchange single energy quantum between two different macroscopic quantum systems
- Summary & Prospects

- Superconductivity and Josephson circuit QED

## How to Get to the Venue

**Hogil Kim Memorial Building**- The workshop will be held in the Hogil Kim Memorial Building, that is located inside the POSTECH campus and that hosts the APCTP Headquaters. Please visit the POSCO IC homepage, http://www.poscoic.co.kr/, for more information.

**APCTP**- The APCTP homepage, http://apctp.org/, provides a complete information about how to arrive from various places including airports and train stations.

## Accommodation

**POSCO International Center**- Homepage: http://www.poscoic.co.kr/
- This hotel is located inside the POSTECH campus. The price is around 80,000 KRW per night (you have to tell them that you're attending the workshop; otherwise, they will charge you the normal price, which is about 120,000 KRW).

**Hotel YEONGILDAE**- Homepage: http://hotelyid.co.kr/
- This hotel is within a walking distance (about 20 minutes) from the POSTECH campus. The price is around 70,000 KRW per night.

**Other Hotels/Motels**- There are many motels and hotels close to the
**Pohang Bus Terminal**(not Express Bus Terminal). The price ranges from 30,000 KRW to 60,000 KRW per night for different motels.

- There are many motels and hotels close to the