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arXiv:2608.09518 · New Journal of Physics

Compound beams for direct experimental comparison of quantum operations

Kishore Thapliyal, Jan Perina, Pavel Pavlicek, Antonin Cernoch

quant-phSubmitted Aug 10, 2026• Announced Aug 11, 2026• 0 citations• Revised Oct 14, 2026 (v2)

v1 · Aug 10, 2026 v2 · Oct 14, 2026

Abstract

Compound beams composed of simple experimental blocks (detected in simultaneous detection windows) that form specific quantum-correlated structures are suggested for simulating the properties of different quantum operations used for creating highly nonclassical and entangled multi-mode states needed in quantum communication, metrology, and information protocols. Qualitative and quantitative comparison of multi-photon addition and subtraction in compound multi-mode thermal as well as sub-Poissonian beams and multi-mode twin beams with their intensities extending over two orders in magnitude is provided. Adding and subtracting up to twenty photocounts, optimal conditions for the generation of experimental nonclassical states are identified. In general, photon addition is identified as advantageous over photon subtraction for the multi-mode thermal and sub-Poissonian beams: It induces (enhances) the nonclassicality in the former (latter) state. Contrary to this, photon subtraction outperforms photon addition in the multi-mode twin beams. Moreover, exploiting temporal photon-pair correlations in compound twin beams when post-selecting, nearly ideal experimental photon(s) addition is demonstrated. The results apply for the beams with mean photon number per mode much less than one.

Journal reference: New J. Phys. 28, 104511 (2026)
DOI: 10.1088/1367-2630/aeae64
Comments: Photon addition and subtraction are systematically compared across twin-beam, thermal, and sub-Poissonian states at varying intensities over two orders in magnitude. Version published in New Journal of Physics

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We have devised an experimentally realizable model generating twin-beam states whose individual beam photon statistics are varied from thermal to Poissonian (by temporal mode averaging) keeping the nonclassical mode correlation intact. We have studied the usefulness of these states for loss measurement by considering three different estimators, comparing with the correlated thermal twin-beam states generated from spontaneous parametric down conversion or four-wave mixing. We then incorporated the photon subtraction operation into the model and demonstrated their performance in loss estimations with respect to unsubtracted states at both fixed squeezing and per photon exposure of the absorbing sample. For instance, at fixed squeezing, for two photon subtraction, up to three times advantage is found. An unexpected result in the latter case is that in some operating regimes the photon subtraction scheme can also give up to

20%

advantage over the correlated thermal beam result and no advantages are obtained when the statistics of each beam turns to Poissonian. We have also made a comparative study of these estimators for finding the best measurement for loss estimations. We present results for all the values of the model parameters changing the statistics of twin-beam states from thermal to Poissonian.

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