SciPost Submission Page
Dissipation and noise in strongly driven Josephson junctions
by Vasilii Vadimov, Yoshiki Sunada, Mikko Möttönen
This is not the latest submitted version.
Submission summary
| Authors (as registered SciPost users): | Vasilii Vadimov |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2504.06877v2 (pdf) |
| Code repository: | https://doi.org/10.5281/zenodo.15301744 |
| Date submitted: | April 29, 2025, 10:16 a.m. |
| Submitted by: | Vadimov, Vasilii |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
|
| Approach: | Theoretical |
Abstract
In circuit quantum electrodynamical systems, the quasiparticle-related losses in Josephson junctions are suppressed due to the gap in the superconducting density of states which is much higher than the typical energy of a microwave photon. In this work, we show that a strong drive even at a frequency lower than twice the superconductor gap parameter can activate dissipation in the junctions due to photon-assisted breaking of the Cooper pairs. Both the decay rate and noise strength associated with the losses are sensitive to the dc phase bias of the junction and can be tuned in a broad range by the amplitude and the frequency of the external driving field, making the suggested mechanism potentially attractive for designing tunable dissipative elements. We also predict pronounced memory effects in the driven Josephson junctions, which are appealing for both theoretical and experimental studies of non-Markovian physics in superconducting quantum circuits. We illustrate our theoretical findings by studying the spectral properties and the steady-state population of a low-impedance resonator coupled to the driven Josephson junction: we show the emergence of non-Lorentzian spectral lines and broad tunability of effective temperature of the steady state.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Current status:
Reports on this Submission
Report
Recommendation
Accept in alternative Journal (see Report)
Strengths
Weaknesses
Report
The authors present a theoretical analysis of dissipation and memory effects in superconducting Josephson junctions under strong microwave drive.
The article almost meets all the requirements: it provides a link between cQED, mesoscopic physics (using out-of-equilibrium Keldysh formalism). The paper is written clearly in a logically structured way, however the heavy formalism used might be a problem for non-experts (hence it would benefit from more physical intuition as mentioned before). The derivations are traceable, literature is cited properly, and the results are summarized properly. I found the introduction and abstract to be very clear.
I think the article is timely and relevant to the cQED& mesoscopic physics community, however a few points should be clarified:
- To my understanding, the authors assume an equilibrium fermi-dirac distribution of quasiparticles. However, it is often the case that the quasiparticle distribution deviates significantly from equilibrium (due to cosmic rays for example)
- It also seems that the authors do not consider possible changes in the quasiparticle distribution under driving. It would be helpful to clarify under what realistic conditions this effect can be safely neglected
- The finite quality factor of the resonator does not appear to be included in the model. However, some of the rates shown in Fig. 7(b) become comparable to resonator photon lifetimes that happen in experiments
Requested changes
- It would be helpful to explicitly state which specific singularities of the admittance are responsible for the sharp transitions observed in Figs. 7(a) and 7(b).
Recommendation
Ask for minor revision
We are thankful to Referee for their high evaluation of our work. Below, we answer to the issues raised by Referee:
-
As Referee correctly noted, we consider Fermi-Dirac distribution of quasiparticles in superconducting leads. The distribution function appears in polarization operators through Keldysh component of quasiclassical Green's functions in Eq. (6). In case of non-thermal distribution of quasiparticles, hyperbolic tangent function in Eq. (6) should be replaced by [1 - 2 n_\alpha(\hbar \omega)], where n_\alpha(\varepsilon) is mean population of quasiparticles with energy \varepsilon in the lead \alpha. Equilibrium distribution of quasiparticles is also implicitly assumed in expression for Keldysh component of polarization operator in Eq. (5). We have updated that equation with general expression and highlight that it reduces to FDT in equilibrium case.
-
To take account of possible quasiparticle distribution change, one has to go beyond second order approximation w.r.t. tunneling in Eq. (39). The small parameter for this approximation is R_K/R_J, where R_K = 2\pi \hbar / e^2 ~ 25.8 kOhm . Therefore, for highly resistive junctions we can use fixed distribution of quasiparticles. We have added a comment on this issue to Sec. 2.1.
-
In this work, we focused on a single decay channel caused by quasiparticles in the Josephson junction. Other loss mechanisms, e.g. coupling to Ohmic resistors, can be just added into action Eq. (2). In our analysis in Sec. 4, we assume coupling to the input/output ports to be infinitesimal merely to reduce number parameters and simplify the presentation.
-
We have written which resonances are responsible for the sharp transitions in Fig. 7 in the caption to that figure. We have also added paragraph to the main text where we clarify which multiphoton processes are dominant in each of the regions visible in Fig. 7.
Author: Vasilii Vadimov on 2025-08-20 [id 5749]
(in reply to Report 2 on 2025-08-18)We are thankful to Referee for their overall positive report on our manuscript, even though they did not find it suitable for publication in SciPost Physics due to lack of novelty. We have decided to follow their and Editor's-in-charge recommendation and resubmit the manuscript to SciPost Physics Core.