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How to optimize the absorption of two entangled photons
by E. G. Carnio, A. Buchleitner, F. Schlawin
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Submission summary
| Authors (as registered SciPost users): | Edoardo Carnio |
| Submission information | |
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| Preprint Link: | scipost_202106_00027v1 (pdf) |
| Date submitted: | 2021-06-16 17:48 |
| Submitted by: | Carnio, Edoardo |
| Submitted to: | SciPost Physics Core |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
We investigate how entanglement can enhance two-photon absorption in a three-level system. First, we employ the Schmidt decomposition to determine the entanglement properties of the optimal two-photon state to drive such a transition, and the maximum enhancement which can be achieved in comparison to the optimal classical pulse. We then adapt the optimization problem to realistic experimental constraints, where photon pairs from a down-conversion source are manipulated by local operations such as spatial light modulators. We derive optimal pulse shaping functions to enhance the absorption efficiency, and compare the maximal enhancement achievable by entanglement to the yield of optimally shaped, separable pulses.
Current status:
Reports on this Submission
Report #2 by Shaul Mukamel (Referee 1) on 2021-6-23 (Invited Report)
- Cite as: Shaul Mukamel, Report on arXiv:scipost_202106_00027v1, delivered 2021-06-23, doi: 10.21468/SciPost.Report.3107
Report
This is an interesting study since the field of quantum light spectroscopy is rapidly growing.
The authors explore the problem of what is the optimal two-photon state for entangled two-photon absorption (ETPA) for a three-level system. They showed that the optimal state is essentially the entangled photon state emitted from the model. Realistic pulse shaping and optimization relevant to current experimental design are further discussed.
The authors first present the optimal entangled-photon wavefunction for enhancing two-photon absorption in a simple three-level system and then discuss the relation between the entanglement and signal enhancement. This is certainly an interesting topic, considering the very weak entangled two-photon absorption cross section. This question has largely been answered in the paper of one of the authors titled “Theory of coherent control with quantum light” 2017 New J. Phys. 19 013009. In the first half of the manuscript, the authors mostly repeat what has been done there.
The new thing in this manuscript is the adaption of the optimization problem into a realistic experimental setting. The authors consider the optimal local pulse shaping on each photon of the pairs produced by spontaneous parametric down-conversion and the optimal shaping on the pump. However, the authors only consider a very simple and unrealistic three-level model system. In order to be experimentally relevant, the authors should address a realistic molecular model.
Overall, although this manuscript has some potentially interesting results, they are not sufficiently novel and practical enough to warrant publication in SciPost Physics.
Here are some additional comments
The langrage multiplier only guarantees that ⟨n_1 n_2 ⟩=1, this does not guarantee a two-photon state with each mode containing a single photon. This should be addressed.
The three-level model is too simple to represent a molecule. A discussion of how the complexity of a manifold of e and f states would affect the conclusions will be very useful.
Since the f-state in the model has a finite lifetime, a more meaningful target to optimize would be the fluorescence rate from the f-state instead of the f-state population.
To define quantum enhancement, the authors compare the ETPA with the signal using only the first Schmidt mode. This classical reference with a single Schmidt mode is difficult, if not impossible, to measure in experiments. A better classical reference would be the optimal unentangled state that maximize the absorption probability, which can be obtained by using the same optimization procedure as for quantum light.
5 .The critical recent work of Raymer on the (un)fesibility. of entangled TPA should be discussed. https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-13-20022&id=451846
Report #1 by Anonymous (Referee 2) on 2021-6-20 (Invited Report)
- Cite as: Anonymous, Report on arXiv:scipost_202106_00027v1, delivered 2021-06-20, doi: 10.21468/SciPost.Report.3087
Strengths
The paper is a comprehensive account of a quantum viewpoint of
two photon absorption with emphasis on the role of entanglement.
The paper explores quantum control of the photon field to enhance
or even saturate the two photon absorption.
The authors also formulate the optimization with the use of an SLM
which is directly relevant for experiment.
Weaknesses
The paper is dedicated to weak field excitation. as a result the atomic response function is almost trivial. As a result the role of interfering pathways for control is minimal.
Report
The paper is clear and well written.
The authors describe the main aspects of the theory.
The paper is therefore lengthly but considering the comprehensive
overview it is appropriate.