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REVIEW 3 major objections 4 minor 1 cited by

Replacing passive interferometers with optical parametric amplifier networks keeps Gaussian boson sampling classically hard even when photon loss is present, because the output entanglement continues to scale linearly with mode number.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

T0 review · deepseek-v4-flash

2026-08-03 19:21 UTC pith:VYRX7JN5

load-bearing objection A genuinely new architecture for loss-robust GBS, but the hardness-under-loss claim is not proven because linear E_N does not imply exponential MPS/MPO cost. the 3 major comments →

arxiv 2512.00753 v2 pith:VYRX7JN5 submitted 2025-11-30 quant-ph

Boosting Gaussian Boson Sampling using Optical Parametric Amplification Networks

classification quant-ph
keywords Gaussian boson samplingoptical parametric amplifierSU(1,1) interferometerlogarithmic negativityphoton losscomputational hardnessHafnianquantum advantage
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper argues that inserting optical parametric amplifiers (OPAs) into the interferometer of Gaussian boson sampling creates an active network that replenishes entanglement lost to photon loss. The authors show numerically that the output state's logarithmic negativity grows linearly with the number of modes even at realistic transmittance, whereas in a passive interferometer loss makes entanglement grow sublinearly and enables classical simulation. Since linear entanglement growth is their criterion for exponential cost of tensor-network classical simulation, they conclude this 'OPA-boosted GBS' preserves #P-hard sampling complexity in lossy conditions. If correct, this would give a practical route to quantum computational advantage that tolerates optical loss.

Core claim

In standard GBS a lossy linear interferometer is equivalent to a lossless one with weaker squeezing, so loss reduces entanglement and can make the output classically simulable. The paper proposes replacing beam splitters with two-mode squeezers (OPAs) arranged in layers, so the network itself injects nonclassicality. The output probabilities still have Hafnian form, hence the sampling problem remains #P-hard. Using logarithmic negativity computed from the output covariance matrix, the paper reports that with vacuum inputs the entanglement grows linearly with both squeezing parameter and network depth in the lossless case, and—crucially—that under photon loss with transmittance down to 0.6 (a

What carries the argument

The central object is the SU(1,1) network: a multilayer array of optical parametric amplifiers described by two-mode squeezing operations, interleaved with beam-splitter layers that model photon loss. The symplectic covariance-matrix formalism tracks the Gaussian state through the network; the output photon-number distribution is given by the Hafnian master theorem, keeping the #P-hard complexity of GBS. The entanglement measure is logarithmic negativity EN, computed from symplectic eigenvalues of the partially transposed covariance matrix. The argument's load-bearing step is the numerical finding that EN grows linearly with mode number n under loss, which the paper links to the known result

Load-bearing premise

The claim that the scheme is classically intractable under loss rests on the numerical observation—for at most 10 modes and transmittance at least 0.4—that logarithmic negativity grows linearly with mode number, and on the assumption that this linear growth of a mixed-state entanglement measure forces exponential cost for tensor-network classical simulation.

What would settle it

A direct calculation of logarithmic negativity for more than 10 modes (say n=20 or 40) at transmittance values around 0.4–0.6 that shows sublinear growth with mode number would refute the paper's central scaling claim; alternatively, demonstrating an MPO/MPS classical algorithm that approximates the OPA-network output distribution to constant error in polynomial time for these parameters would refute the hardness conclusion even if the scaling holds.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • If correct, the scheme offers a loss-tolerant photonic platform for quantum computational advantage, avoiding the need for extremely low-loss interferometers.
  • The equivalence between lossy passive GBS and weaker-squeezing lossless GBS is broken; loss cannot be lumped into a single transmissivity, so input squeezing cannot be tuned to mimic the effect.
  • The OPA network can be pumped synchronously and is experimentally feasible with current pulsed-laser and frequency-decoupling techniques.
  • Since the input need not be squeezed vacuum, the noncompact SU(1,1) structure may allow even harder sampling problems than standard GBS.
  • The linear entanglement scaling indicates that tensor-network algorithms that efficiently simulate current GBS experiments under loss would fail for this scheme.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The paper's complexity argument assumes that linear scaling of logarithmic negativity (a mixed-state entanglement measure) with mode number forces exponential bond dimension for MPS/MPO simulation. This is an extrapolation from the converse result about sublinear entanglement; a direct simulation algorithm for this specific state would settle it.
  • The numerical evidence covers n up to 10 and transmittance down to 0.4; experimental realizations will have inhomogeneous loss and phase errors, which may alter the scaling. Testing the scheme with larger n or with local loss imbalance would be a natural next step.
  • If the hardness claim holds, the same OPA-network idea could be applied to other Gaussian sampling tasks, e.g., threshold detection or scattershot settings, to restore loss-robustness.
  • The paper does not provide a full approximate-sampling hardness proof (e.g., under noise models with constant error), so the practical complexity gap remains open; a rigorous reduction would strengthen the claim.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

3 major / 4 minor

Summary. The paper proposes replacing the passive SU(2) interferometer in Gaussian Boson Sampling (GBS) with an active network of optical parametric amplifiers (OPAs) forming an SU(1,1) interferometer. The authors derive the covariance-matrix transformation for this network, including a model of photon loss via interleaved beam-splitter layers, and note that the output click probabilities are still given by a Hafnian (Eq. 3). They numerically compute the logarithmic negativity E_N for up to n=10 modes, d=20 layers, and transmittances t in [0.4,1]. They report linear scaling of E_N with squeezing r and depth d in the lossless case, and approximately linear scaling of E_N with mode number n under realistic loss. From this they conclude that the OPA-boosted scheme remains classically hard to simulate under loss, in contrast to standard passive GBS. The manuscript includes appendices with the symplectic derivation, the lossy-channel composition, a Bloch-Messiah argument, and a comparison table of boson-sampling variants.

Significance. The idea of injecting nonclassicality inside the interferometer to counteract loss is timely and, if rigorously supported, would be an important contribution to the photonic quantum-advantage program. The paper uses standard Gaussian-state tools, and the numerical simulations are transparent and reproducible with open-source software; no parameters are fitted to a target result. However, the two load-bearing steps—(i) the bridge from E_N scaling to tensor-network simulation cost, and (ii) the step from exact Hafnian hardness to approximate sampling hardness under loss—are not established. The paper is therefore more a proposal with encouraging numerics than a definitive proof of loss-robust hardness; the claims can be strengthened by direct bond-dimension or approximate-sampling analysis.

major comments (3)
  1. [Entanglement section; Fig. 3(e); Discussion; Appendix D Table I] The paper's central assertion that the scheme 'sustains computational hardness' under loss (Discussion) rests on the numerical observation that 'EN continues to scale linearly with the number of modes even under lossy conditions' (Fig. 3(e), d=8, r=0.8). This inference is not justified. Refs. [18-20] prove only that sublinear entanglement entropy suffices for efficient MPS/MPO simulation; they do not establish that linear logarithmic negativity forces exponential bond dimension. E_N is a mixed-state entanglement monotone, not the von Neumann or operator entanglement entropy that controls MPS/MPO bond dimension for Gaussian states. A product of n independent two-mode squeezed states with local loss has E_N ~ n yet is exactly simulable with O(1) bond dimension. To support Table I's 'Cannot be classically simulated using MPS/MPO [19,20]', the authors must compute the relevant bond dimension
  2. [Computational complexity section, Eq. (3)] The argument from Eq. (3) to sampling hardness is incomplete. Eq. (3) gives an exact Hafnian expression for a single output probability. Exact Hafnian #P-hardness does not imply that approximate sampling from the lossy distribution is classically hard, particularly in the presence of noise. The standard GBS hardness proof requires average-case hardness of the Hafnian, anticoncentration, and a noise-robustness argument. The manuscript does not provide these elements, nor does it explain how the cited works [41,42] apply to the OPA network. Without this framework, the statement in the text that 'the same complexity restrictions that apply to linear GBS also extend to our scheme' is too strong.
  3. [Fig. 3(e), Discussion] The asymptotic claim that E_N 'scales linearly with the number of modes even under lossy conditions' is supported by only five data points (n=2,4,6,8,10) at d=8, r=0.8, t>=0.6. No error bars or fits are reported, and the smallest transmittance in this panel is t=0.6, while the text and Fig. 3(c) refer to t=0.4. Given the central role of this scaling, the numerical evidence should be extended to larger n and a wider loss range, and the slope and fit quality should be reported to justify the asymptotic extrapolation.
minor comments (4)
  1. [Abstract] The phrase 'a more effective implementations' is ungrammatical. In addition, the abstract's statement that the scaling results 'suggest that classical simulation in lossy scenarios remains computationally intractable' overstates what the numerics can show without the missing complexity analysis.
  2. [Eq. (3)] The displayed formula for p({n_k}) is typeset incorrectly; it should read p({n_k}) = haf(W̃({n_k})) / (sqrt(det(I+G)) ∏_k n_k!). As written, the square root and product are misplaced, which obscures the meaning.
  3. [References] Refs. [22], [41], and [42] are cited only in Appendix D but are directly relevant to the main complexity discussion; consider moving them into the main text. Also, in the Computational Complexity section, 'in the complexity class #P' should be '#P-complete' for permanent and Hafnian functions.
  4. [Eq. (5)] Please state that the logarithm in F(x) is natural and that E_N is the Gaussian-state logarithmic negativity obtained from the symplectic eigenvalues of the partially transposed covariance matrix. This is standard but should be made explicit for the non-specialist reader.

Circularity Check

0 steps flagged

No significant circularity; the derivation is self-contained.

full rationale

The paper's central claims are (i) the output distribution of the OPA network retains the Hafnian/#P-hard structure, and (ii) the logarithmic negativity E_N remains linear in the number of modes under loss, implying hardness for tensor-network simulation. Neither claim reduces to its own inputs by construction. The Hafnian form (Eq. 3) follows from the standard Gaussian-state formalism via the Hafnian master theorem; it is not imposed to obtain a desired hardness conclusion. The quantity E_N is computed directly from the covariance matrix derived from the Hamiltonian and the loss model (Eqs. 1-7, Appendix B); no parameter is fitted to any target output, and no predicted quantity is a renamed fit parameter. The parameters r, d, n, t are scanned model inputs, not inferred from the E_N results. Refs [18-20] are cited for the relation between entanglement scaling and classical simulation, and while the inference from linear E_N to exponential MPS/MPO cost is not fully proven in the paper, this is a logical gap or an overreach in the hardness argument, not a circularity. The cited results are external and are not used in a self-consistent way to define the conclusion. The appendix's demonstration of inequivalence between SU(1,1) and SU(2) networks under loss is a technical result, not an assumed conclusion. Overall, no step in the derivation chain equates the prediction with the input, so the circularity score is 0.

Axiom & Free-Parameter Ledger

4 free parameters · 7 axioms · 0 invented entities

No new entities are introduced. The central claim rests on four hand-chosen uniform parameters and three domain assumptions: the Hafnian theorem, the unproven E_N-to-hardness bridge, and the beam-splitter loss model. The loss-noncommutation result is a clean derived fact within the standard Gaussian-channel formalism.

free parameters (4)
  • uniform squeezing parameter r = 0-3 (illustrative sweep)
    Chosen uniformly across all OPAs and layers; the numerical scaling claims depend on this uniformity and the scanned range.
  • uniform transmittance t = 0.4-1 (loss sweep)
    Chosen identically for all beam-splitter loss layers; the 'realistic loss' claim depends on this simplified uniform-loss model.
  • network depth d = up to 20 layers
    Chosen to reach full connectivity in the numerics; the linear-vs-depth claim is made only once full connectivity is achieved.
  • number of modes n = 2-10 in main scaling figures
    The central linear-in-n claim is extrapolated from these small system sizes; no data beyond n=10 is provided.
axioms (7)
  • standard math Hafnian master theorem: photon-number probabilities of the output Gaussian state are given by Hafnians (Eq. 3)
    Used to claim #P-hardness of the output probability distribution.
  • domain assumption Underlying complexity-theoretic assumptions (e.g., average-case hardness, Permanent-of-Gaussian) needed to convert Hafnian #P-hardness into approximate-sampling hardness
    The paper cites Refs [1,8] but does not verify these conjectures for the OPA-boosted, lossy distribution.
  • domain assumption Tensor-network simulation becomes inefficient exactly when logarithmic negativity (or entanglement entropy) scales linearly with mode number
    Load-bearing bridge from E_N scaling to hardness; cited Refs [18-20,36] only establish the sufficient direction for entanglement entropy, not E_N for mixed states.
  • domain assumption Photon loss is modeled by beam-splitter layers with vacuum environment between OPA layers, while OPA layers themselves are lossless
    Standard but optimistic; intrinsic loss inside the nonlinear medium is neglected, which could change the steady-state entanglement.
  • domain assumption Uniform squeezing r and transmittance t across all modes/layers, with phase-locked synchronized pumping experimentally feasible
    Needed for the numerical scaling; realization of a phase-locked many-mode OPA network is nontrivial and not demonstrated.
  • standard math Bloch-Messiah decomposition reduces the lossless SU(1,1) network to standard GBS (Appendix C)
    Used to argue the new effect appears only in the lossy regime.
  • standard math Gaussian channel composition rules and complete positivity condition (Appendix C)
    Used to prove that loss does not commute through squeezing, the key structural distinction from SU(2) interferometers.

pith-pipeline@v1.3.0-alltime-deepseek · 16386 in / 15510 out tokens · 156888 ms · 2026-08-03T19:21:39.486004+00:00 · methodology

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read the original abstract

Gaussian Boson Sampling (GBS) provides a route toward demonstrating quantum computational advantage. However, optical loss, which reduces the entanglement in the system, can render GBS results classically simulable. We propose a nonlinear photonic architecture based on optical parametric amplifiers (OPAs) arranged in an interferometer network. This active configuration amplifies quantum correlations within the circuit while preserving the #P-hard Hafnian structure of the output probabilities. Using logarithmic negativity, we numerically show that entanglement scales linearly with both the OPA gain and network depth in the lossless limit, and maintains linear scaling with the number of modes under realistic loss rate. These scaling behaviors suggest that classical simulation in lossy scenarios remains computationally intractable. Our results demonstrate that OPA-boosted GBS preserves computational hardness in noisy environments, offering a more effective implementations of near-term photonic quantum computers.

Figures

Figures reproduced from arXiv: 2512.00753 by Chuan-Feng Li, Guang-Can Guo, Xiao-Ye Xu, Yukuan Zhao.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) depicts the model of a lossy GBS. The inputs are single-mode squeezed states (SMSS) going through a lossy linear [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (a). For a given partition strategy, the entangle￾ment grows with increasing squeezing [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Logarithmic negativity ( [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗

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Reference graph

Works this paper leans on

46 extracted references · 3 linked inside Pith · cited by 1 Pith paper

  1. [1]

    Aaronson and A

    S. Aaronson and A. Arkhipov, The computational com- plexity of linear optics, inProceedings of the Forty- Third Annual ACM Symposium on Theory of Computing (ACM, 2011) p. 333–342

  2. [2]

    B. T. Gard, K. R. Motes, J. P. . Olson, P. P. Rohde, and J. P. Dowling, An introduction to boson-sampling, inFrom Atomic to Mesoscale(WS, 2015) p. 167–192

  3. [3]

    Neville, C

    A. Neville, C. Sparrow, R. Clifford, E. Johnston, P. M. Birchall, A. Montanaro, and A. Laing, Classical boson sampling algorithms with superior performance to near- term experiments, Nature Physics13, 1153 (2017)

  4. [4]

    Tillmann, B

    M. Tillmann, B. Daki´ c, R. Heilmann, S. Nolte, A. Sza- meit, and P. Walther, Experimental boson sampling, Na- ture Photonics7, 540 (2013)

  5. [5]

    J. B. Spring, B. J. Metcalf, P. C. Humphreys, W. S. Kolthammer, X.-M. Jin, M. Barbieri, A. Datta, N. Thomas-Peter, N. K. Langford, D. Kundys, J. C. Gates, B. J. Smith, P. G. R. Smith, and I. A. Walms- ley, Boson sampling on a photonic chip, Science339, 798 (2013)

  6. [6]

    M. A. Broome, A. Fedrizzi, S. Rahimi-Keshari, J. Dove, S. Aaronson, T. C. Ralph, and A. G. White, Photonic boson sampling in a tunable circuit, Science339, 794 (2013)

  7. [7]

    H. Wang, J. Qin, X. Ding, M.-C. Chen, S. Chen, X. You, Y.-M. He, X. Jiang, L. You, Z. Wang, C. Schneider, J. J. Renema, S. H¨ ofling, C.-Y. Lu, and J.-W. Pan, Boson sampling with 20 input photons and a 60-mode interfer- ometer in a 10 14-dimensional hilbert space, Phys. Rev. Lett.123, 250503 (2019)

  8. [8]

    C. S. Hamilton, R. Kruse, L. Sansoni, S. Barkhofen, C. Silberhorn, and I. Jex, Gaussian boson sampling, 7 Phys. Rev. Lett.119, 170501 (2017)

  9. [9]

    Zhong, H

    H.-S. Zhong, H. Wang, Y.-H. Deng, M.-C. Chen, L.-C. Peng, Y.-H. Luo, D. Wu, S.-Q. Gong, H.-L. Liu, L. Li, N.-L. Liu, C.-Y. Lu, J.-W. Pan,et al., Quantum compu- tational advantage using photons, Science 10.1126/sci- ence.abe8770 (2020)

  10. [10]

    Zhong, Y.-H

    H.-S. Zhong, Y.-H. Deng, J. Qin, H. Wang, M.-C. Chen, L.-C. Peng, Y.-H. Luo, D. Wu, S.-Q. Gong, H. Su, Y. Hu, P. Hu, X.-Y. Yang, W.-J. Zhang, H. Li, Y. Li, X. Jiang, L. Gan, G. Yang, L. You, Z. Wang, L. Li, N.- L. Liu, J. J. Renema, C.-Y. Lu, and J.-W. Pan, Phase- programmable gaussian boson sampling using stimu- lated squeezed light, Phys. Rev. Lett. 10....

  11. [11]

    Deng, Y.-C

    Y.-H. Deng, Y.-C. Gu, H.-L. Liu, S.-Q. Gong, H. Su, Z.- J. Zhang, H.-Y. Tang, M.-H. Jia, J.-M. Xu, M.-C. Chen, J. Qin, L.-C. Peng, J. Yan, Y. Hu, J. Huang, H. Li, Y. Li, Y. Chen, X. Jiang, L. Gan, G. Yang, L. You, L. Li, H.- S. Zhong, H. Wang, N.-L. Liu, J. J. Renema, C.-Y. Lu, and J.-W. Pan, Gaussian boson sampling with pseudo- photon-number-resolving de...

  12. [12]

    H.-L. Liu, H. Su, S.-Q. Gong, Y.-C. Gu, H.-Y. Tang, M.-H. Jia, Q. Wei, Y. Song, D. Wang, M. Zheng, F. Chen, L. Li, S. Ren, X. Zhu, M. Wang, Y. Chen, Y. Liu, L. Song, P. Yang, J. Chen, H. An, L. Zhang, L. Gan, G. Yang, J.-M. Xu, Y.-M. He, H. Wang, H.-S. Zhong, M.-C. Chen, X. Jiang, L. Li, N.-L. Liu, Y.-H. Deng, X.-L. Su, Q. Zhang, C.-Y. Lu, and J.-W. Pan, ...

  13. [13]

    L. S. Madsen, F. Laudenbach, M. F. Askarani, F. Rortais, T. Vincent, J. F. F. Bulmer, F. M. Miatto, L. Neuhaus, L. G. Helt, M. J. Collins, A. E. Lita, T. Gerrits, S. W. Nam, V. D. Vaidya, M. Menotti, I. Dhand, Z. Vernon, N. Quesada, and J. Lavoie, Quantum computational ad- vantage with a programmable photonic processor, Nature 606, 75 (2022)

  14. [14]

    Aaronson and D

    S. Aaronson and D. J. Brod, Bosonsampling with lost photons, Phys. Rev. A93, 012335 (2016)

  15. [15]

    Rahimi-Keshari, T

    S. Rahimi-Keshari, T. C. Ralph, and C. M. Caves, Suffi- cient conditions for efficient classical simulation of quan- tum optics, Phys. Rev. X6, 021039 (2016)

  16. [16]

    Garc ´ ıa-Patr´ on, J

    R. Garc ´ ıa-Patr´ on, J. J. Renema, and V. Shchesnovich, Simulating boson sampling in lossy architectures, Quan- tum3, 169 (2019)

  17. [17]

    Oszmaniec and D

    M. Oszmaniec and D. J. Brod, Classical simulation of photonic linear optics with lost particles, New Journal of Physics20, 092002 (2018)

  18. [18]

    C. Oh, K. Noh, B. Fefferman, and L. Jiang, Classical simulation of lossy boson sampling using matrix product operators, Phys. Rev. A104, 022407 (2021)

  19. [19]

    C. Oh, M. Liu, Y. Alexeev, B. Fefferman, and L. Jiang, Classical algorithm for simulating experimental gaussian boson sampling, Nature Physics20, 1461 (2024)

  20. [20]

    M. Liu, C. Oh, J. Liu, L. Jiang, and Y. Alexeev, Simulat- ing lossy gaussian boson sampling with matrix-product operators, Phys. Rev. A108(2023)

  21. [21]

    M. S. Kim, W. Son, V. Buˇ zek, and P. L. Knight, Entan- glement by a beam splitter: Nonclassicality as a prereq- uisite for entanglement, Phys. Rev. A65, 032323 (2002)

  22. [22]

    Spagnolo, D

    N. Spagnolo, D. J. Brod, E. F. Galv˜ ao, and F. Sciarrino, Non-linear boson sampling, npj Quantum Information9, 3 (2023)

  23. [23]

    B. R. Mollow and R. J. Glauber, Quantum theory of parametric amplification. i, Phys. Rev.160, 1076 (1967)

  24. [24]

    Yurke, S

    B. Yurke, S. L. McCall, and J. R. Klauder, Su(2) and su(1,1) interferometers, Phys. Rev. A33, 4033 (1986)

  25. [25]

    C. Shen, Z. Zhang, and L.-M. Duan, Scalable implemen- tation of boson sampling with trapped ions, Phys. Rev. Lett.112, 050504 (2014)

  26. [26]

    Bl¨ umel, Nonlinear dynamics of trapped ions, Physica Scripta1995, 369 (1995)

    R. Bl¨ umel, Nonlinear dynamics of trapped ions, Physica Scripta1995, 369 (1995)

  27. [27]

    Harder, T

    G. Harder, T. J. Bartley, A. E. Lita, S. W. Nam, T. Ger- rits, and C. Silberhorn, Single-mode parametric-down- conversion states with 50 photons as a source for meso- scopic quantum optics, Physical Review Letters116, 143601 (2016)

  28. [28]

    Patera, N

    G. Patera, N. Treps, C. Fabre, and G. J. de Valc´ arcel, Quantum theory of synchronously pumped type i optical parametricoscillators: characterization of the squeezed supermodes, The European Physical Journal D56, 123 (2010)

  29. [29]

    V. A. Averchenko, Y. M. Golubev, C. Fabre, and N. Treps, Quantum correlations and fluctuations in the pulsed light produced by a synchronously pumped op- tical parametricoscillator below its oscillation threshold, The European Physical Journal D61, 207 (2011)

  30. [30]

    Weedbrook, S

    C. Weedbrook, S. Pirandola, R. Garc ´ ıa-Patr´ on, N. J. Cerf, T. C. Ralph, J. H. Shapiro, and S. Lloyd, Gaussian quantum information, Rev. Mod. Phys.84, 621 (2012)

  31. [31]

    V. V. Kocharovsky, V. V. Kocharovsky, and S. V. Tarasov, The hafnian master theorem, Linear Algebra and its Applications651, 144 (2022)

  32. [32]

    Bj¨ orklund, B

    A. Bj¨ orklund, B. Gupt, and N. Quesada, A faster hafnian formula for complex matrices and its benchmarking on a supercomputer (2019), arXiv:1805.12498

  33. [33]

    M. B. Plenio, Logarithmic negativity: A full entangle- ment monotone that is not convex, Phys. Rev. Lett.95, 090503 (2005)

  34. [34]

    M. M. Wolf, J. Eisert, and M. B. Plenio, Entangling power of passive optical elements, Phys. Rev. Lett.90, 047904 (2003)

  35. [35]

    Cariolaro and G

    G. Cariolaro and G. Pierobon, Reexamination of bloch- messiah reduction, Phys. Rev. A93(2016)

  36. [36]

    Or´ us and J

    R. Or´ us and J. I. Latorre, Universality of entanglement and quantum-computation complexity, Phys. Rev. A69, 052308 (2004)

  37. [37]

    T. R. Bromley, J. M. Arrazola, S. Jahangiri, J. Izaac, N. Quesada, A. D. Gran, M. Schuld, J. Swinarton, Z. Zabaneh, and N. Killoran, Applications of near-term photonic quantum computers: software and algorithms, Quantum Science and Technology5, 034010 (2020)

  38. [38]

    Killoran, J

    N. Killoran, J. Izaac, N. Quesada, V. Bergholm, M. Amy, and C. Weedbrook, Strawberry fields: A software plat- form for photonic quantum computing, Quantum3, 129 (2019)

  39. [39]

    G. S. Agarwal,Quantum Optics(Cambridge University Press, 2012)

  40. [40]

    ˇSafr´ anek, Gaussian quantum metrology and space- time probes (2016)

    D. ˇSafr´ anek, Gaussian quantum metrology and space- time probes (2016)

  41. [41]

    Shchesnovich, Distinguishing noisy boson sampling from classical simulations, Quantum5, 423 (2021)

    V. Shchesnovich, Distinguishing noisy boson sampling from classical simulations, Quantum5, 423 (2021)

  42. [42]

    C. Oh, L. Jiang, and B. Fefferman, On classical sim- ulation algorithms for noisy boson sampling (2023), arXiv:2301.11532

  43. [43]

    scattershot bosonsampling: A new ap- 8 proach to scalable bosonsampling experiments

    S. Aaronson, “scattershot bosonsampling: A new ap- 8 proach to scalable bosonsampling experiments”, Blog post on Shtetl-Optimized (2013), posted November 8 2013

  44. [44]

    Zhong, Y

    H.-S. Zhong, Y. Li, W. Li, L.-C. Peng, Z.-E. Su, Y. Hu, Y.-M. He, X. Ding, W. Zhang, H. Li, L. Zhang, Z. Wang, L. You, X.-L. Wang, X. Jiang, L. Li, Y.-A. Chen, N.- L. Liu, C.-Y. Lu, and J.-W. Pan, 12-photon entan- glement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down- conversion, Phys. Rev. Lett. , 250505 (2018)

  45. [45]

    Barkhofen, T

    S. Barkhofen, T. J. Bartley, L. Sansoni, R. Kruse, C. S. Hamilton, I. Jex, and C. Silberhorn, Driven boson sam- pling, Phys. Rev. Lett. , 020502 (2017)

  46. [46]

    one lumped loss+ lossless SU(1,1) network

    N. Quesada, J. M. Arrazola, and N. Killoran, Gaussian boson sampling using threshold detectors, Phys. Rev. A , 062322 (2018). 9 Appendix A: Derivation of the Covariance Matrix Representation of the Output State Without Loss The Hamiltonian associated with an optical parametric amplifier (OPA) isH=ℏ(ξˆa †ˆb† −ξ ∗ˆaˆb), whereξ=−re iθ. The corresponding Bogo...