Content

This is the joint module page of LV1370 "Supraleitende Quantenschaltkreise" and LV2475 "Cavity-, Circuit- und Waveguide-QED".

Within the seminars, students present state-of-the-art developments in modern quantum technology with superconducting quantum circuits. In this field, funamental research in academia has meanwhile triggered highly dynamical activities from established large corporations (Google, IBM, Intel etc.) and ambitious startups (Rigetti, IQM, HQS etc.). In particular, superconducting quantum circuits belong to the few prime candidates for a scalable quantum computer.

Time/Place

Tuesdays 12:15 - 14:00h, WMI-Seminarroom, room 143

Schedule

Below, you will find a list of papers we picked for the seminar. Please have a look, identify a paper that interests you and let me know which one you would like to present in the seminar until the 13th of May. 

You will be put in contact with a tutor, that will help you in preparing the slides for your presentation. Typically, you will have one or two sessions with your tutor.  

We will organize a schedule for the seminar talks, and I would ask you to keep the timeslot of the seminar free, and also join the presentations of your peers. Until the schedule is released, there will not be a seminar! After release, we will follow the schedule. 

Your seminar talk should be about 30 minutes long, with 10-15 minutes of scientific discussion afterwards. 

List of open topics for seminar talks in SS 2025:

Quantum Computing:

1. Logical quantum processor based on reconfigurable atom arrays (Nature,   Lukin (Hrvard/MIT)),
   https://www.nature.com/articles/s41586-023-06927-3
2. Combining quantum processors with real-time classical communication (Nature,  IBM),
   https://www.nature.com/articles/s41586-024-08178-2
3. Fast flux-activated leakage reduction for superconducting quantum circuits (PRL, Wallraff),
   https://doi.org/10.1103/PhysRevLett.134.120601
4. Realizing Lattice Surgery on Two Distance-Three Repetition Codes with Superconducting Qubits (Arxiv, Wallraff)
   https://arxiv.org/abs/2501.04612
5. Deterministic remote entanglement using a chiral quantum interconnect (Nature, Oliver (MIT))
   https://doi.org/10.1038/s41567-025-02811-1
6. Quantum error correction below the surface code threshold (Nature, Google)
   https://arxiv.org/abs/2408.13687
7. Hardware efficient quantum error correction via concatenated bosonic qubits (Nature, Painter)
   https://www.nature.com/articles/s41586-025-08642-7
8. Quantum error detection in qubit-resonator star architecture  (arxiv, Deppe (IQM))
   https://doi.org/10.48550/arXiv.2503.12869
9. Encoding a magic state with beyond break-even fidelity, (Nature, IBM),
   https://www.nature.com/articles/s41586-023-06846-3
10. Stabilization of Kerr-cat qubits with quantum circuit refrigerator (NPJ Quan. Inf., Tomonaga)
    https://arxiv.org/abs/2406.13957
11. Performance Stabilization of High-Coherence Superconducting Qubits (Arxiv, IBM),
    https://arxiv.org/abs/2503.12514
12. Quasiparticle poisoning of superconducting qubits with active gamma irradiation (Arxiv, Plourde)
    https://doi.org/10.48550/arXiv.2503.0735
13. All-optical superconducting qubit readout (Nature, Fink),
    https://www.nature.com/articles/s41567-024-02741-4
14. Quantum control of a cat qubit with bit-flip times exceeding ten seconds (Leghtas),
    https://arxiv.org/pdf/2307.06617

Superconducting Circuits

1. Generation of genuine entanglement up to 51 superconducting qubits (Pan, Hefei),
   https://www.nature.com/articles/s41586-023-06195-1
2. Dual-rail encoding with superconducting cavities (Schoelkopf, Yale),
   https://www.pnas.org/doi/abs/10.1073/pnas.2221736120
3. High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler (Oliver, MIT),
   https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.031035
4. Cloaking a qubit in a cavity  (Huard/ Blais , Lyon/Sherbrooke),
   https://www.nature.com/articles/s41467-023-42060-5
5. On-demand directional microwave photon emission using waveguide quantum electrodynamics (Oliver, MIT), 
   https://www.nature.com/articles/s41567-022-01869-5
6. Millisecond Coherence in a Superconducting Qubit  (Manucharyan),
   https://doi.org/10.1103/PhysRevLett.130.267001
7. Quantum Simulation of Topological Zero Modes on a 41-Qubit Superconducting Processor (Heng Fan, Hefei),
   https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.080401

Quantum Sensing

1. Correlation Spectroscopy with Multiqubit-Enhanced Phase Estimation (Roos, Blatt , Innsbruck),
   https://journals.aps.org/prx/abstract/10.1103/PhysRevX.14.011033
2. High-sensitivity AC-charge detection with a MHz-frequency fluxonium qubit (Deleglise, CNRS),
   https://journals.aps.org/prx/abstract/10.1103/PhysRevX.14.011007
3. Quantum advantage in microwave quantum radar (Huard, Lyon),
   https://doi.org/10.1038/s41567-023-02113-4

Hybrid Quantum Systems

1. Quantum-enabled millimetre wave to optical transduction using neutral atoms (Schuster, Simon, Stanford),
   https://www.nature.com/articles/s41586-023-05740-2
2. Single electron-spin-resonance detection by microwave photon counting (Flurin, Bertet, CEA Saclay),
   https://www.nature.com/articles/s41586-023-06097-2

Research papers with focus on theory:

Dissipative phase transition/QPS:

• Exact Duality at Low Energy in a Josephson Tunnel Junction Coupled to a Transmission Line (Ciuti, CNRS),
  https://arxiv.org/abs/2504.14651
  Supplemental material:
  - Resilience of the quantum critical line in the Schmid transition (Ciuti, CNRS), https://doi.org/10.1103/PhysRevB.111.064509
  - Emergent quantum phase transition of a Josephson junction coupled to a high-impedance multimode resonator (Ciuti, CNRS), https://doi.org/10.1038/s41467-024-48558-w

Superinductance:

• Symmetries and Collective Excitations in Large Superconducting Circuits (Koch, Northwestern),
  https://doi.org/10.1103/PhysRevX.3.011003
  Supplemental material:
  - Experiments: Microwave characterization of Josephson junction arrays: implementing a low loss superinductance (Devoret, Yale), https://doi.org/10.1103/PhysRevLett.109.137002
  - Supplemental theory: Consistent Quantization of Nearly Singular Superconducting Circuits (DiVincenzo, RWTH), https://doi.org/10.1103/PhysRevX.13.021017

State preparation in Open Quantum Systems:

• Accelerating Dissipative State Preparation with Adaptive Open Quantum Dynamics (Clerk, Chicago), https://doi.org/10.1103/PhysRevLett.134.050603

Couplers:

• Balanced coupling in electromagnetic circuits (Atalaya, Google),
  https://doi.org/10.1103/PhysRevApplied.23.024012
  Supplemental material:
  - Experimental realization: Suppressing Counter-Rotating Errors for Fast Single-Qubit Gates with Fluxonium (Oliver, MIT), https://doi.org/10.1103/PRXQuantum.5.040342

New Qubits:

• Dissipative cats: Enhancing dissipative cat qubit protection by squeezing (Murani,A&B),
  https://doi.org/10.48550/arXiv.2502.07892

Driven dissipative systems:

1. Inducing Nonclassical Lasing via Periodic Drivings in Circuit Quantum Electrodynamics (Porras, CSIC),
   https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.193601
2. Waveguide QED with dissipative light-matter couplings (Nori, RIKEN),
   https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.L012036

Many-body quantum optics:

1. Deterministic generation of photonic entangled states using decoherence-free subspaces (Asenjo-Garcia, Columbia),
   https://arxiv.org/abs/2410.03325
2. Universal scaling laws for correlated decay of many-body quantum systems (Asenjo-Garcia, Columbia),
   https://arxiv.org/abs/2406.00722

Non-Markovian waveguide QED: 

• Multimode-cavity picture of non-Markovian waveguide QED (Ciccarello, Palermo),
  https://arxiv.org/abs/2403.07110

Topical directions of the seminar:

• Foundations and applications of superconducting quantum circuits in quantum computing, quantum simulation, quantum communication, quantum sensing, and quantum metrology.
• Superconducting quantum technology: Resonators, waveguides, quantum bits, couplers, quantum-limited amplifiers, quantum processors, quantum error correction etc.
• State-of-the-art fabrication and measurement tachniques for superconducting quantum circuits.
• Investigation of the fundamental light-matter interaction "on a chip" using superconducting quantum circuits.
• Quantum information theoretical concepts: Entanglement, quantum gates, quantum algorithms, quantum memories, quantum measurements etc.
• The coupling of nanomechanical systems and spin ensembles to superconducting circuits.
• Challenges: longer quantum coherence, higher gate fidelities, scalability to a large number of qubits etc.
• Latest developments on the strive towards quantum advantages over conventional technology
• Propagating quantum microwaves emitted by superconducting circuits: quantum ressources, quantum microwave communication, quantum radar

You will be supported in the preparation of your talks from the research groups on superconducting quantum circuits, propagating quantum microwaves, and nanomechanics at the Walther-Meißner-Institute.

Learning Outcome:

After the successful completion of the module the students are able

• To prepare presentation slides on a scientific topic and to clearly present a topical research field within a scientific talk.
• To discuss on a state-of-the-art research field in a scientific way.
• To analyze and assess the latest development in quantum scinece and technology with superconducting circuits.
• To understand and explain the foundations of superconducting quantum systems and technology.
• To understand the foundations and the state of the art in quantum computing, quantum simulation, quantum communication, quantum sensing, and quantum metrology with supercondcuting circuits
• To understand the foundations and the state of the art in nanomechnical systems and spin ensembles

Preconditions:

Basic knowledge of condensed matter physics, foundations of quantum mechanics