SciPost Submission Page
Experimental protocol for observing single quantum many-body scars with transmon qubits
by Peter Græns Larsen, Anne E. B. Nielsen, André Eckardt, Francesco Petiziol
Submission summary
| Authors (as registered SciPost users): | Francesco Petiziol |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2410.14613v1 (pdf) |
| Date submitted: | 2024-10-24 18:39 |
| Submitted by: | Petiziol, Francesco |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
Quantum many-body scars are energy eigenstates which fail to reproduce thermal expectation values of local observables in systems, where the rest of the many-body spectrum fulfils eigenstate thermalization. Experimental observation of quantum many-body scars has so far been limited to models with multiple scar states. Here we propose protocols to observe single scars in architectures of fixed-frequency, fixed-coupling superconducting qubits. We first adapt known models possessing the desired features into a form particularly suited for the experimental platform. We develop protocols for the implementation of these models, through trotterized sequences of two-qubit cross-resonance interactions, and verify the existence of the approximate scar state in the stroboscopic effective Hamiltonian. Since a single scar cannot be detected from coherent revivals in the dynamics, differently from towers of scar states, we propose and numerically investigate alternative and experimentally-accessible signatures. These include the dynamical response of the scar to local state deformations, to controlled noise, and to the resolution of the Lie-Suzuki-Trotter digitization.
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
Strengths
1 - The paper provides a very detailed experimental protocol on how to observe quantum scars in a superconducting system.
2 - It establishes a very good link between quantum many-body scars and superconducting circuits and opens a pathway towards new proposals for quantum many-body phenomenon.
3 - The paper is well-organized and structured.
Weaknesses
1 - The paper lacks the comparison between single quantum many-body scars and tower of scars states and why the former is interesting and also difficult to observe.
Report
In their manuscript, authors propose a protocol for the experimental observation of a single Quantum Many-Body Scar (QMBS). QMBSs are interesting due to their implications for thermalization theory and potential applications in quantum technologies, however authors claim that the experimental evidence so far has been limited to systems with towers of scar states.
The authors build on the theoretical framework presented in Ref. [10], where a family of 1D spin-1/2 models with single scar states was introduced. In this work, they identify specific Hamiltonians that can be realized experimentally using transmon qubits with fixed nearest neighbor couplings.
A key strength of the paper lies in its methodological innovation. It proposes novel experimental signatures to detect a single quantum scar state, combining trotterized dynamics, local observable measurements, and entanglement entropy quantification. I especially liked Fig. 1 where they describe the experimental procedure visually. Moreover, the paper is well organized, starting from an introduction to quantum many-body scars, setting the stage for the building blocks of the experiments, and to further validation of their proposed protocol through numerical simulations.
Overall, I liked the paper and I think it deserves a publication in SciPost Physics. However, I propose some changes in the manuscript to make this nice paper even better.
Requested changes
1) Introduction to QMBS: I really believe that a more extensive introduction to QMBS would be helpful for the reader.
2) Detailed explanation and comparison between single and tower of scar states: I think for a non-expert, the introduction really lacks a detailed explanation on both what is meant by single quantum scars and tower of scar states. The only relevant reference authors provide is Ref. [10] and this downgrades the paper's generality.
And a final suggestion:
3) Code and data availability: While the authors provide a lot of detail about their numerical simulations, publishing the code they used for the simulations would greatly enhance the impact of the paper.
Recommendation
Ask for minor revision