Sensitivity Evaluation of SU(1,1) Interferometers with Arbitrary Input Probe State and Homodyne Detections
Pith reviewed 2026-05-22 05:57 UTC · model grok-4.3
The pith
A general derivation gives the phase sensitivity of SU(1,1) interferometers for arbitrary inputs and with losses included under homodyne detection.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The phase sensitivity of SU(1,1) interferometers is obtained through closed-form expressions that remain valid for arbitrary input states and that explicitly include internal and external losses; these expressions reveal that improvements occur through noise reduction, signal amplification, or both, depending on the chosen configuration.
What carries the argument
General analytical expressions for phase sensitivity derived from the quadrature operators after parametric amplification and homodyne detection.
If this is right
- The single-output detection scheme with equal-gain amplifiers remains most robust when internal losses become very large.
- For a two-mode coherent input state the expressions identify which combination of amplification and detection yields the lowest phase uncertainty at any given loss level.
- Sensitivity improvements can be traced to either quadrature noise suppression or signal magnification in each specific setup.
- The same framework permits direct numerical comparison of all listed configurations to select the best one for a measured loss value.
Where Pith is reading between the lines
- The same loss-inclusive formulas could be used to rank candidate input states before an experiment is built.
- Applying the derivation to other detection schemes such as photon counting would show whether homodyne remains optimal under high loss.
- The robustness ranking for equal-gain single-port detection suggests a practical starting point for lossy quantum sensors.
Load-bearing premise
Internal and external losses act as independent linear loss channels on the modes after the parametric amplifiers, without additional noise or mode mismatch.
What would settle it
A laboratory measurement of phase sensitivity in a lossy SU(1,1) interferometer with a known input state that falls outside the interval predicted by the general formula for the corresponding detection and gain settings.
Figures
read the original abstract
We provide a general theoretical derivation of the phase sensitivity achieved by SU(1,1) interferometers under homodyne detection. The general expressions obtained accommodate arbitrary input states and include internal and external losses. In this systematic review, both full SU(1,1) interferometers with two parametric amplifiers and the truncated interferometers with only one parametric amplifier are examined. We investigate scenarios involving both single-output ports and joint homodyne detection, and consider parametric amplifiers with equal gains or with a boosted gain second amplifier. Our analytical formulation provides physical insight and understanding of the improvements in the sensitivity, which are shown to originate from noise reduction and/or signal amplification, depending on the configurations and practical implementations. Surprisingly, the configuration with single-output mode detection and parametric amplifiers with equal gains exhibits the highest robustness to very high internal losses. We finally apply this framework to a ubiquitous $|\alpha,0\rangle$ input two-mode coherent probe state. This approach permits the comparison of different strategies and the optimization of the interferometer performance in the presence of losses. In particular, we determine which amplification and detection configurations provide the best performance, depending on the level of losses. This exemplifies how this general analytical approach provides a powerful tool to design quantum-enhanced interferometers and achieve optimal sensitivity with selected probe states and homodyne detection.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a general theoretical derivation of the phase sensitivity achieved by SU(1,1) interferometers under homodyne detection. The expressions accommodate arbitrary input probe states and include internal and external losses. It examines both full interferometers with two parametric amplifiers and truncated versions with one, considers single-output and joint homodyne detection, and compares equal-gain versus boosted-gain amplifiers. The framework is applied to the two-mode coherent state |α,0⟩ to compare configurations, optimize performance under losses, and identify that single-output detection with equal gains is most robust to high internal losses, with improvements traced to noise reduction or signal amplification.
Significance. If the derivations hold, the work supplies a systematic analytical tool for quantum metrology that enables direct comparison of amplification and detection strategies for arbitrary inputs in the presence of losses. The closed-form expressions and the identification of a robust equal-gain single-output configuration provide concrete physical insight and practical guidance for experimental design, which are strengths of the manuscript.
major comments (1)
- [Loss-modeling section (derivation of homodyne quadrature means and variances)] Loss-modeling section (derivation of homodyne quadrature means and variances): the assumption that internal and external losses act as independent linear loss channels (beam-splitter equivalents) placed after the parametric amplifiers omits possible intra-amplifier noise or spatial/temporal mode mismatch. These effects would add extra vacuum fluctuations and alter the reported quadrature variances, particularly for entangled or non-Gaussian inputs; the central sensitivity formulas and the claimed robustness of the equal-gain single-output case at high internal loss rest directly on this modeling choice.
minor comments (1)
- [Introduction and theoretical framework] Notation for the input-state parameters and the two gain values G1, G2 is introduced late; defining them explicitly in the opening theoretical section would improve readability.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and the constructive comment on the loss-modeling assumptions. We address the point below and indicate the planned revision.
read point-by-point responses
-
Referee: Loss-modeling section (derivation of homodyne quadrature means and variances): the assumption that internal and external losses act as independent linear loss channels (beam-splitter equivalents) placed after the parametric amplifiers omits possible intra-amplifier noise or spatial/temporal mode mismatch. These effects would add extra vacuum fluctuations and alter the reported quadrature variances, particularly for entangled or non-Gaussian inputs; the central sensitivity formulas and the claimed robustness of the equal-gain single-output case at high internal loss rest directly on this modeling choice.
Authors: We thank the referee for this observation. Our derivation models internal and external losses via independent beam-splitter equivalents with vacuum modes inserted after the parametric amplifiers, which is the standard approximation used throughout the quantum-metrology literature to obtain closed-form expressions. We agree that this simplified model does not incorporate intra-amplifier noise or spatial/temporal mode mismatch; such effects would indeed introduce additional vacuum fluctuations and could modify the quadrature variances, particularly when the input states are entangled or non-Gaussian. The reported robustness of the equal-gain single-output configuration is therefore established within the framework of this conventional loss model. In the revised manuscript we will add an explicit paragraph in the loss-modeling section stating these modeling assumptions, referencing the standard nature of the approach, and noting that more detailed treatments of intra-amplifier dynamics or mode mismatch could be incorporated for specific experimental scenarios. This addition will clarify the scope and limitations of the analytic results without altering the central formulas. revision: yes
Circularity Check
Derivation is self-contained from standard input-output relations
full rationale
The paper derives closed-form phase sensitivity expressions for SU(1,1) interferometers by starting from the input-output relations of parametric amplifiers and homodyne quadrature measurements, then incorporating internal and external losses as independent beam-splitter channels acting after the amplifiers. These steps yield explicit means and variances for arbitrary input states without fitting any parameter to the target sensitivity or invoking self-citations for uniqueness or ansatz. The application to the |α,0⟩ coherent state is a direct substitution into the general formulas. The central results therefore remain independent of the final claims and do not reduce to their inputs by construction.
Axiom & Free-Parameter Ledger
axioms (2)
- standard math Parametric amplifiers are described by the standard SU(1,1) transformation with gain parameter r.
- domain assumption Losses are modeled as independent beam-splitter channels with transmissivity η.
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We provide a general theoretical derivation of the phase sensitivity achieved by SU(1,1) interferometers under homodyne detection. The general expressions obtained accommodate arbitrary input states and include internal and external losses.
-
IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Internal and external losses are modeled by fictitious beam splitters placed inside and outside the interferometer (losses Ls, Li, ls, and li).
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
Albert A Michelson and Edward W Mor- ley. On the relative motion of the earth and the luminiferous ether.American jour- nal of science, 3(203):333–345, 1887. DOI: https://doi.org/10.2475/ajs.s3-34.203.333
-
[2]
Peter J De Groot. A review of selected topics in interferometric optical metrology.Reports on Progress in Physics, 82(5):056101, 2019. DOI: 10.1088/1361-6633/ab092d
-
[3]
ShumingYangandGuofengZhang. Areview of interferometry for geometric measure- ment. Measurement Science and Technology, 29(10):102001, 2018. DOI: 10.1088/1361- 6501/aad732
-
[4]
Fiber-optic interferometry-based heart rate monitoring
Rene Jaros, Jan Nedoma, Stanislav Kepak, and Radek Martinek. Fiber-optic interferometry-based heart rate monitoring. IEEE Transactions on Instrumentation and Measurement, 71:1–15, 2022. DOI: https://doi.org/10.1109/TIM.2022.3178495
-
[5]
doi:10.1103/PhysRevLett.116.061102 , keywords =
Benjamin P Abbott, Richard Abbott, Thomas D Abbott, Matthew R Aber- nathy, Fausto Acernese, Kendall Ackley, Carl Adams, Thomas Adams, Paolo Addesso, Rana X Adhikari, et al. Ob- servation of gravitational waves from a binary black hole merger. Physical review letters, 116(6):061102, 2016. DOI: https://doi.org/10.1103/PhysRevLett.116.061102
-
[6]
Masahiro Takeoka, Kaushik P Seshadreesan, Chenglong You, Shuro Izumi, and Jonathan P Dowling. Fundamental preci- sion limit of a mach-zehnder interferometric sensor when one of the inputs is the vacuum. Physical Review A, 96(5):052118, 2017. DOI: https://doi.org/10.1103/PhysRevA.96.052118
-
[7]
Quantum-mechanical noise in an interferometer
Carlton M Caves. Quantum-mechanical noise in an interferometer. Physical Review D , 23(8):1693, 1981. DOI: https://doi.org/10.1103/PhysRevD.23.1693
-
[8]
Enhanced in- terferometry using squeezed thermal states and even or odd states
Qing-Shou Tan, Jie-Qiao Liao, Xiaoguang Wang, and Franco Nori. Enhanced in- terferometry using squeezed thermal states and even or odd states. Physi- cal Review A, 89(5):053822, 2014. DOI: https://doi.org/10.1103/PhysRevA.89.053822
-
[9]
Quantum optical metrology–the lowdown on high-n00n states
Jonathan P Dowling. Quantum optical metrology–the lowdown on high-n00n states. Contemporary physics, 49(2):125–143, 2008. DOI: https://doi.org/10.1080/00107510802091298
-
[10]
Mach-zehender interferometry at the heisenberg limit with coherent and squeezed-vaccum light
Pezze Luca and Smerzi Augusto. Mach-zehender interferometry at the heisenberg limit with coherent and squeezed-vaccum light. Phys. Rev. Lett., 100(7):073601, 2008. DOI: https://doi.org/10.1103/PhysRevLett.100.073601
-
[11]
Su (2) and su (1, 1) interferometers
Bernard Yurke, Samuel L McCall, and John R Klauder. Su (2) and su (1, 1) interferometers. Physical Review A , 33(6):4033, 1986. DOI: https://doi.org/10.1103/PhysRevA.33.4033
-
[12]
Coherent-light-boosted, sub-shot noise, quantum interferometry
William N Plick, Jonathan P Dowling, and Girish S Agarwal. Coherent-light-boosted, sub-shot noise, quantum interferometry. 17 New Journal of Physics, 12(8):083014, 2010. DOI: 10.1088/1367-2630/12/8/083014
-
[13]
A broadband fiber-optic nonlinear interferometer
Joseph M Lukens, Raphael C Pooser, and Nicholas A Peters. A broadband fiber-optic nonlinear interferometer. Ap- plied Physics Letters, 113(9), 2018. DOI: https://doi.org/10.1063/1.5048198
-
[14]
Yuhong Liu, Jiamin Li, Liang Cui, Nan Huo, Syed M Assad, Xiaoying Li, and ZY Ou. Loss-tolerant quantum dense metrology with su (1, 1) interferometer.Op- tics express, 26(21):27705–27715, 2018. DOI: https://doi.org/10.1364/OE.26.027705
-
[15]
Yuhong Liu, Nan Huo, Jiamin Li, Liang Cui, Xiaoying Li, and Zheyu Jeff Ou. Optimum quantum resource distribution for phase measurement and quantum information tapping in a dual-beam su (1, 1) interferometer. Optics Ex- press, 27(8):11292–11302, 2019. DOI: https://doi.org/10.1364/OE.27.011292
-
[16]
Detection loss tolerant supersensitive phase measurement with an su (1, 1) interferometer
Mathieu Manceau, Gerd Leuchs, Farid Khalili, and Maria Chekhova. Detection loss tolerant supersensitive phase measurement with an su (1, 1) interferometer. Physical review letters, 119(22):223604, 2017. DOI: https://doi.org/10.1103/PhysRevLett.119.223604
-
[17]
U. Seyfarth, A. B. Klimov, H. de Guise, G. Leuchs, and L. L. Sanchez-Soto. Wigner function for SU(1,1). Quantum, 4:317, September 2020. ISSN 2521-327X. DOI: 10.22331/q-2020-09-07-317. URL https:// doi.org/10.22331/q-2020-09-07-317
-
[18]
Pumped-up su (1, 1) interferometry
Stuart S Szigeti, Robert J Lewis-Swan, and Simon A Haine. Pumped-up su (1, 1) interferometry. Physical Review Letters, 118(15):150401, 2017. DOI: https://doi.org/10.1103/PhysRevLett.118.150401
-
[19]
Su (2)-in-su (1, 1) nested in- terferometer for highly sensitive, loss- tolerant quantum metrology
Wei Du, Jia Kong, Jun Jia, Sheng Ming, Chun-Hua Yuan, JF Chen, ZY Ou, Morgan W Mitchell, and Weiping Zhang. Su (2)-in-su (1, 1) nested in- terferometer for highly sensitive, loss- tolerant quantum metrology. arXiv preprint arXiv:2004.14266, 2020. DOI: https://doi.org/10.48550/arXiv.2004.14266
-
[20]
Phase esti- mation via a number-conserving operation inside a su (1, 1) interferometer
Qingqian Kang, Zekun Zhao, Teng Zhao, Cunjin Liu, and Liyun Hu. Phase esti- mation via a number-conserving operation inside a su (1, 1) interferometer. Physi- cal Review A, 110(2):022432, 2024. DOI: https://doi.org/10.1103/PhysRevA.110.022432
-
[21]
Taj Kumar, Aviral Kumar Pandey, Anand Kumar, and Devendra Kumar Mishra. Enhancement in phase sensitivity in displacement-assisted su(1,1) interferometer via photon recycling. APL Quantum, 2 (1), March 2025. ISSN 2835-0103. DOI: 10.1063/5.0245187
- [22]
-
[23]
interferometers: Basic principles and ap- plications. APL Photonics, 5(8), 2020. DOI: https://doi.org/10.1063/5.0004873
-
[24]
Nan Huo, Xueshi Guo, Wen Zhao, Yunx- iao Zhang, Xiaoying Li, and Z. Y. Ou. Su(1,1) interferometer by direct detection. In 2021 Conference on Lasers and Electro- Optics (CLEO), pages 1–2, 2021
work page 2021
-
[25]
The phase sensitivity of an su (1, 1) interferometer with coherent and squeezed-vacuum light
Dong Li, Chun-Hua Yuan, ZY Ou, and Weiping Zhang. The phase sensitivity of an su (1, 1) interferometer with coherent and squeezed-vacuum light. New Jour- nal of Physics, 16(7):073020, 2014. DOI: 10.1088/1367-2630/16/7/073020
-
[26]
Su (1, 1) interferometry with parity measure- ment
Shuai Wang and Jian-Dong Zhang. Su (1, 1) interferometry with parity measure- ment. Journal of the Optical Society of America B, 38(9):2687–2693, 2021. DOI: https://doi.org/10.1364/JOSAB.430759
-
[27]
Luo, Harald Her- rmann, Christine Silberhorn, and Polina R
Alessandro Ferreri, Matteo Santandrea, Michael Stefszky, Kai H. Luo, Harald Her- rmann, Christine Silberhorn, and Polina R. Sharapova. Spectrally multimode inte- grated SU(1,1) interferometer.Quantum, 5: 461, May 2021. ISSN 2521-327X. DOI: 10.22331/q-2021-05-27-461. URL https:// doi.org/10.22331/q-2021-05-27-461
-
[28]
Conclusive pre- cision bounds for su (1, 1) interferometers
ChenglongYou, SushovitAdhikari, Xiaoping Ma, Masahide Sasaki, Masahiro Takeoka, and Jonathan P Dowling. Conclusive pre- cision bounds for su (1, 1) interferometers. Physical Review A, 99(4):042122, 2019. DOI: https://doi.org/10.1103/PhysRevA.99.042122
-
[29]
Quantum interferometry with and without an external phase reference
Marcin Jarzyna and Rafał Demkowicz- Dobrzański. Quantum interferometry with and without an external phase reference. Physical Review A—Atomic, Molecular, and Optical Physics, 85(1):011801, 2012. DOI: https://doi.org/10.1103/PhysRevA.85.011801
-
[30]
Optimal phase measure- ments with bright-and vacuum-seeded su (1, 1) interferometers
Brian E Anderson, Bonnie L Schmittberger, Prasoon Gupta, Kevin M Jones, and 18 Paul D Lett. Optimal phase measure- ments with bright-and vacuum-seeded su (1, 1) interferometers. Physical Review A , 95(6):063843, 2017. DOI: https://doi.org/10.1103/PhysRevA.95.063843
-
[31]
Jasper Kranias, Guillaume Thekkadath, Khabat Heshami, and Aaron Z. Gold- berg. Metrological Advantages in Seeded and Lossy Nonlinear Interferometers.Quan- tum, 9:1619, February 2025. ISSN 2521-327X. DOI: 10.22331/q-2025-02-04-
-
[32]
URLhttps://doi.org/10.22331/q- 2025-02-04-1619
work page doi:10.22331/q- 2025
-
[33]
Phase sensing beyond the standard quantum limit with a vari- ation on the su (1, 1) interferome- ter
Brian E Anderson, Prasoon Gupta, Bon- nie L Schmittberger, Travis Horrom, Carla Hermann-Avigliano, Kevin M Jones, and Paul D Lett. Phase sensing beyond the standard quantum limit with a vari- ation on the su (1, 1) interferome- ter. Optica, 4(7):752–756, 2017. DOI: https://doi.org/10.1364/OPTICA.4.000752
-
[34]
Optimized phase sensing in a truncated su (1, 1) interferometer
Prasoon Gupta, Bonnie L Schmittberger, Brian E Anderson, Kevin M Jones, and Paul D Lett. Optimized phase sensing in a truncated su (1, 1) interferometer. Op- tics express, 26(1):391–401, 2018. DOI: https://doi.org/10.1364/OE.26.000391
-
[35]
Florian Hudelist, Jia Kong, Cunjin Liu, Jietai Jing, ZY Ou, and Weip- ing Zhang. Quantum metrology with parametric amplifier-based photon cor- relation interferometers. Nature com- munications, 5(1):3049, 2014. DOI: https://doi.org/10.1038/ncomms4049
-
[36]
Effect of losses on the per- formance of an su (1, 1) interferometer
Alberto M Marino, NV Corzo Trejo, and Paul D Lett. Effect of losses on the per- formance of an su (1, 1) interferometer. Physical Review A—Atomic, Molecular, and Optical Physics, 86(2):023844, 2012. DOI: https://doi.org/10.1103/PhysRevA.86.023844
-
[37]
ZY Ou. Enhancement of the phase- measurement sensitivity beyond the standard quantum limit by a nonlin- ear interferometer. Physical Review A—Atomic, Molecular, and Optical Physics, 85(2):023815, 2012. DOI: https://doi.org/10.1103/PhysRevA.85.023815
-
[38]
G. Ferrini, I. Fsaifes, T. Labidi, F. Goldfarb, N. Treps, and F. Bretenaker. Symplectic ap- proach to the amplification process in a non- linear fiber: role of signal-idler correlations and application to loss management.Jour- nal of the Optical Society of America B, 31 (7):1627, June 2014. ISSN 1520-8540. DOI: 10.1364/josab.31.001627. 19 In this appendix...
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.