Topology
We plan to adress the following questions:
- How does topology manifest itself in the physical properties of quantum circuits?
- Can circuits have topological properties that go beyond what is possible with topological matter?
- Can we classify the topology, enumerating all topological invariants, of an arbitrary circuit?
- What are the possible applications in metrology, such as voltage, current, or resistance standards?
- Are there applications that go beyond metrology, such as non-reciprocal non-linear microwave components?
Strong coupling / dissipation
Regarding the effects of dissipation, despite our experiment on the Schmid transition Ref. 4, there is still controversy, both among experimentalists and theorists, on how a resistor affects transport through a Josephson junction. With our recent theoretical work Ref. 5, and designing new experiments with it, we hope to quell controversy and achieve consensus in the community in the next five years. Indeed, a straightforward generalization of the method introduced in Ref. 5 will enable to accurately predict the equilibrium behavior of Josephson junctions (or qubits) coupled to frequency-structured environment with arbitrary strength, something that was not previously possible and where we had to rely on intuition, or heuristically obtained approximate theories.
Coupling quantum circuits to the exterior : strong coupling and/or dissipation.
Despite our experiment on the Schmid transition [1], there is still controversy, both among experimentalists and theorists, on how a resistor affects transport through a Josephson junction. With our recent theoretical work [2], and designing new experiments with it, we hope to quell controversy and achieve consensus in the community in the next five years. Indeed, a straightforward generalization of the method introduced in [2] will enable to accurately predict the equilibrium behavior of Josephson junctions (or qubits) coupled to frequency-structured environment with arbitrary strength, something that was not previously possible and where we had to rely on intuition, or heuristically obtained approximate theories.
[1] A. Murani et al., Absence of a dissipative quantum phase transition in Josephson junctions, Phys. Rev. X 10, 021003 (2020)., see also Phys. Rev. X 11, 018002 (2021)
[2] C. Altimiras et al., Absence of a dissipative quantum phase transition in Josephson junctions: Theory arXiv:2312.14754 (2023), submitted to SciPost.
[3] L. Peyruchat et al., Spectral Signatures of Nontrivial Topology in a Superconducting Circuit, Phys. Rev. X 14, 041041 (2024).