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arxiv: 2512.00481 · v2 · submitted 2025-11-29 · 🪐 quant-ph

A Concatenated Dual Displacement Code for Continuous-Variable Quantum Error Correction

Pith reviewed 2026-05-17 03:21 UTC · model grok-4.3

classification 🪐 quant-ph
keywords continuous-variable quantum error correctionGKP statesanalog Steane codeconcatenated codesGaussian displacement errorslattice-crossing eventsfault-tolerant quantum computation
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The pith

Concatenating GKP-based Gaussian suppression with an outer analog Steane code reduces displacement error variance by up to 50 percent in continuous-variable systems and corrects lattice-crossing events without bias.

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

The paper establishes that nesting a Gaussian-noise-suppression circuit using GKP ancillary qumodes inside an outer analog Steane code yields complementary protection against both small continuous displacements and larger abrupt errors while remaining inside the continuous encoding space. This duality allows the inner layer to shrink Gaussian variance and the outer layer to detect and fix lattice crossings that exceed the GKP correctable range. A sympathetic reader would care because the construction relaxes the squeezing threshold for the inner code, keeps success probability set by the ratio of residual error to crossing size, and thereby opens a concrete route to fault-tolerant continuous-variable quantum computation.

Core claim

Under infinite squeezing the concatenated code suppresses the variance of Gaussian displacement errors across all qumodes by up to 50 percent while enabling unbiased correction of lattice-crossing events, with success probability determined by the ratio between the residual Gaussian error standard deviation and the lattice-crossing magnitude. Even with finite squeezing the architecture continues to deliver both Gaussian-error suppression and lattice-crossing correction, and the presence of the outer analog Steane code relaxes the squeezing requirement of the inner GKP states.

What carries the argument

The concatenated dual displacement code, which places a Gaussian-noise-suppression circuit based on GKP ancillas inside an outer analog Steane code that detects and corrects lattice-crossing and abrupt displacement errors.

If this is right

  • Gaussian-error suppression and lattice-crossing correction persist even when squeezing is finite.
  • The outer Steane layer lowers the squeezing threshold needed for the inner GKP states.
  • The construction supplies a viable architecture for fault-tolerant continuous-variable quantum computation.
  • The approach keeps the encoding continuous rather than mapping to discrete qubits or qudits.

Where Pith is reading between the lines

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

  • Similar inner-outer pairings could be explored for other continuous-variable error types such as loss or dephasing.
  • Resource estimates for near-term experiments could be refined by quantifying how much the outer code reduces total squeezing overhead.
  • The success-probability formula could be evaluated at realistic finite-squeezing levels to predict observable correction rates.

Load-bearing premise

The outer analog Steane code can reliably detect and correct lattice-crossing events and other abrupt displacements without introducing uncorrectable errors or biasing the continuous encoding.

What would settle it

A high-squeezing numerical simulation or experiment that measures the post-correction variance of displacement noise on all qumodes and checks whether it reaches exactly half the uncorrected value while lattice-crossing corrections remain unbiased.

Figures

Figures reproduced from arXiv: 2512.00481 by Frank Mueller, Fucheng Guo, Yuan Liu.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) DV Steane code. (b) Analog Steane code obtained [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) Position-quadrature syndrome extraction circuit. (b) Momentum-quadrature syndrome extraction circuit. Both [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Logical-operation circuits for (a) the displacement [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Gaussian error suppression circuit. [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. The miscorrection probability [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Monte Carlo simulation of the residual displacement [PITH_FULL_IMAGE:figures/full_fig_p012_6.png] view at source ↗
read the original abstract

The continuous-variable (CV) Gaussian no-go theorem fundamentally limits the suppression of Gaussian displacement errors using only Gaussian gates and states. Prior studies have employed Gottesman-Kitaev-Preskill (GKP) states as ancillary qumodes to suppress small Gaussian displacement errors, but when the displacement magnitude becomes large, lattice-crossing events arise beyond the correctable range of the GKP state. To address this issue, we concatenate a Gaussian-noise-suppression circuit with an outer analog Steane code that corrects such occasional lattice-crossing events as well as other abrupt displacement errors. Unlike conventional concatenation, which primarily aims to reduce logical error rates, the Steane-GKP duality in encoding provides complementary protection against both large and small displacement errors, enabling CV error correction within the continuous encoding space and contrasting with earlier approaches that concatenate GKP states with repetition codes for discrete qubit or qudit encodings. Analytical results show that, under infinite squeezing, the concatenated code suppresses the variance of Gaussian displacement errors across all qumodes by up to 50 percent while enabling unbiased correction of lattice-crossing events, with a success probability determined by the ratio between the residual Gaussian error standard deviation and the lattice-crossing magnitude. Even with finite squeezing, the proposed architecture continues to provide Gaussian-error suppression together with lattice-crossing correction, and the presence of the outer analog Steane code relaxes the squeezing requirement of the inner GKP states, indicating near-term experimental feasibility. This work establishes a viable route toward fault-tolerant continuous-variable quantum computation and provides new insight into the design of concatenated CV error-correcting architectures.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript proposes a concatenated dual displacement code for continuous-variable quantum error correction, combining an inner GKP code for small Gaussian displacement errors with an outer analog Steane code to handle large lattice-crossing events. Under infinite squeezing, analytical results claim up to 50% suppression of Gaussian error variance across qumodes and unbiased correction of crossings, with success probability set by the ratio of residual Gaussian std dev to crossing magnitude. The work also addresses finite squeezing, relaxed inner squeezing requirements, and near-term feasibility for fault-tolerant CV quantum computation.

Significance. If the central claims hold, the construction offers a route to complementary protection against both small Gaussian and large abrupt displacements within continuous encodings, potentially bypassing the CV Gaussian no-go theorem via Steane-GKP duality. The reported variance suppression factor and the relaxation of squeezing thresholds would be relevant for experimental CV error correction.

major comments (2)
  1. [Concatenated code construction and Steane-GKP duality section] The central claim of unbiased lattice-crossing correction and the associated success probability (abstract) rests on the outer analog Steane code acting as a perfect, non-disturbing detector that introduces neither residual displacements nor correlations across qumodes; however, the manuscript provides no explicit error-propagation analysis or circuit-level derivation showing the absence of back-action on the inner GKP encoding.
  2. [Analytical results under infinite squeezing] The 50% Gaussian variance suppression under infinite squeezing (abstract) is presented as an analytical result derived from the code structure, but without the full set of defining equations for the concatenated operations or the explicit calculation of the residual error after Steane correction, it is not possible to confirm that the factor is parameter-free or independent of post-hoc assumptions.
minor comments (2)
  1. [Abstract] Clarify whether the 'up to 50 percent' suppression is a worst-case, average, or maximum value and under precisely which error model it is attained.
  2. [Introduction] The introduction would benefit from additional references to prior GKP concatenation schemes and CV no-go theorem results to better situate the novelty of the Steane-GKP duality approach.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable feedback on our manuscript. We address each of the major comments below and outline the revisions we will make to strengthen the presentation of the concatenated code construction and the analytical results.

read point-by-point responses
  1. Referee: [Concatenated code construction and Steane-GKP duality section] The central claim of unbiased lattice-crossing correction and the associated success probability (abstract) rests on the outer analog Steane code acting as a perfect, non-disturbing detector that introduces neither residual displacements nor correlations across qumodes; however, the manuscript provides no explicit error-propagation analysis or circuit-level derivation showing the absence of back-action on the inner GKP encoding.

    Authors: We agree with the referee that an explicit error-propagation analysis would clarify the non-disturbing nature of the outer code. In the revised manuscript, we will add a new subsection providing a circuit-level derivation. This will include the measurement operators for the analog Steane code and demonstrate through error tracking that no additional displacements or correlations are introduced to the inner GKP-encoded qumodes, thereby supporting the unbiased correction and the stated success probability. revision: yes

  2. Referee: [Analytical results under infinite squeezing] The 50% Gaussian variance suppression under infinite squeezing (abstract) is presented as an analytical result derived from the code structure, but without the full set of defining equations for the concatenated operations or the explicit calculation of the residual error after Steane correction, it is not possible to confirm that the factor is parameter-free or independent of post-hoc assumptions.

    Authors: The 50% suppression factor arises directly from the structure of the concatenated code in the infinite squeezing limit, where the outer Steane code effectively averages the residual displacements over the logical basis without adding variance. The defining equations for the concatenated operations are given in Section II of the manuscript, and the residual error calculation is outlined in the analytical results section. To address the concern, we will include an expanded derivation in the appendix, explicitly computing the post-correction variance and confirming its parameter-free nature in this limit. revision: yes

Circularity Check

0 steps flagged

Low circularity; 50% variance suppression derived from concatenated code structure under infinite squeezing

full rationale

The paper's central analytical claim of up to 50% Gaussian variance suppression under infinite squeezing follows from the structural properties of the inner GKP states concatenated with the outer analog Steane code, as stated in the abstract. This result is obtained by direct analysis of the dual displacement encoding rather than by fitting parameters to data or by self-referential definitions that rename inputs as outputs. The invocation of Steane-GKP duality for complementary protection is presented as a known encoding feature enabling unbiased lattice-crossing correction, without reducing the derivation to a load-bearing self-citation chain or an ansatz smuggled from prior author work. No equations or steps in the provided text exhibit the patterns of self-definitional closure, fitted inputs called predictions, or uniqueness imported from the authors themselves. The derivation is therefore self-contained against the stated assumptions and external benchmarks for CV error correction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The proposal rests on standard CV quantum optics assumptions and the existence of GKP states and analog Steane codes from prior literature; no new free parameters or invented entities are introduced in the abstract.

axioms (2)
  • domain assumption GKP states suppress small Gaussian displacements within their correctable range
    Invoked as the inner code's operating principle for the Gaussian-noise-suppression circuit.
  • ad hoc to paper The analog Steane code can correct lattice-crossing events as discrete-like errors in the continuous space
    Central premise enabling the outer code to handle large displacements that exceed the GKP range.

pith-pipeline@v0.9.0 · 5584 in / 1466 out tokens · 38381 ms · 2026-05-17T03:21:02.447866+00:00 · methodology

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Works this paper leans on

58 extracted references · 58 canonical work pages · 2 internal anchors

  1. [1]

    Gaussian Error Suppression 7

  2. [2]

    A Concatenated Dual Displacement Code for Continuous-Variable Quantum Error Correction

    Concatenate Code 8 ∗ fguo22@ncsu.edu † fmuelle@ncsu.edu ‡ q yuanliu@ncsu.edu C. Analysis under Real Conditions 9 D. Experimental Feasibility 10 E. Simulation Results 11 F. Comparison with qubit-based oscillator encoding 12 V. Conclusion 12 Acknowledgments 13 A. Derivation of the Gaussian Error Suppression Formula 13 References 14 I. INTRODUCTION Quantum e...

  3. [3]

    − m√π−ξ (out) x,data 2 σ2 # ×

    Gaussian Error Suppression After the feedforward operation shown in Fig. 4, the residual displacement errors on the data and GKP qumodes are given by ξ(out) x,data =ϵ x,data − 1 2 R2√π(ϵx,data +ϵ x,GKP),(20) 8 ξ(out) p,data =ϵ p,data − 1 2 R2√π(ϵp,data +ϵ p,GKP),(21) ξ(out) x,GKP =ϵ x,GKP − 1 2 R2√π(ϵx,data +ϵ x,GKP),(22) ξ(out) p,GKP =ϵ p,GKP − 1 2 R2√π(...

  4. [4]

    − ϵ2 x,data +ϵ 2 x,GKP 2σ2 # dϵx,data dϵx,GKP = X m∈Z ZZ ϵx,data+ϵx,GKP∈[ 2m√π−√π,2m √π+√π) 1 2πσ 2 δ ξ(out) x,data − 1 2 ϵx,data + 1 2 ϵx,GKP −m √π ×exp

    Concatenate Code The lattice structure of the GKP states enables the suppression of small displacement errors by correcting shifts within each unit cell. However, when the displace- ment magnitude exceeds half of the lattice spacing, a lattice-crossing event occurs. For the proposed concate- nated code, the outer analog Steane code is responsible for corr...

  5. [5]

    P. W. Shor, Scheme for reducing decoherence in quantum computer memory, Phys. Rev. A52, R2493 (1995)

  6. [6]

    A. M. Steane, Error correcting codes in quantum theory, Phys. Rev. Lett.77, 793 (1996)

  7. [7]

    Stabilizer Codes and Quantum Error Correction

    D. Gottesman,Stabilizer Codes and Quantum Error Cor- rection, Ph.D. thesis, California Institute of Technology (1997), arXiv:quant-ph/9705052

  8. [8]

    W. Cai, Y. Ma, W. Wang, C.-L. Zou, and L. Sun, Bosonic quantum error correction codes in superconducting quan- tum circuits, Fundam. Res.1, 50 (2021)

  9. [9]

    A. G. Fowler, M. Mariantoni, J. M. Martinis, and A. N. Cleland, Surface codes: Towards practical large-scale quantum computation, Phys. Rev. A86, 032324 (2012)

  10. [10]

    G. Q. AI, Suppressing quantum errors by scaling a sur- face code logical qubit, Nature614, 676 (2023)

  11. [12]

    M. P. Stafford and N. C. Menicucci, Biased gottesman- kitaev-preskill repetition code, Phys. Rev. A108, 052428 (2023)

  12. [13]

    Li and D

    Z. Li and D. Su, Correcting biased noise using gottesman- kitaev-preskill repetition code with noisy ancilla, Phys. Rev. A109, 052420 (2024)

  13. [14]

    S. L. Braunstein and P. van Loock, Quantum informa- tion with continuous variables, Rev. Mod. Phys.77, 513 (2005)

  14. [15]

    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)

  15. [16]

    Blais, A

    A. Blais, A. L. Grimsmo, S. M. Girvin, and A. Wallraff, Circuit quantum electrodynamics, Rev. Mod. Phys.93, 025005 (2021)

  16. [17]

    Niset, J

    J. Niset, J. Fiur´ aˇ sek, and N. J. Cerf, No-go theorem for gaussian quantum error correction, Phys. Rev. Lett.102, 120501 (2009)

  17. [18]

    B. M. Terhal, Quantum error correction for quantum memories, Rev. Mod. Phys.87, 307 (2015)

  18. [19]

    Y. Xu, Y. Wang, E.-J. Kuo, and V. V. Albert, Qubit- oscillator concatenated codes: Decoding formalism and code comparison, PRX Quantum4, 020342 (2023)

  19. [20]

    Gottesman, A

    D. Gottesman, A. Kitaev, and J. Preskill, Encoding a qubit in an oscillator, Phys. Rev. A64, 012310 (2001)

  20. [21]

    Glancy and E

    S. Glancy and E. Knill, Error analysis for encoding a qubit in an oscillator, Phys. Rev. A73, 012325 (2006)

  21. [22]

    Fukui, A

    K. Fukui, A. Tomita, A. Okamoto, and K. Fujii, High- threshold fault-tolerant quantum computation with ana- log quantum error correction, Phys. Rev. X8, 021054 (2018)

  22. [23]

    K. Noh, S. M. Girvin, and L. Jiang, Encoding an oscilla- tor into many oscillators, Phys. Rev. Lett.125, 080503 (2020)

  23. [24]

    S. L. Braunstein, Error correction for continuous quan- tum variables, Phys. Rev. Lett.80, 4084 (1998)

  24. [25]

    T. Aoki, G. Takahashi, T. Kajiya, J. Yoshikawa, S. L. Braunstein, P. van Loock, and A. Furusawa, Quantum error correction beyond qubits, Nat. Phys.5, 541 (2009)

  25. [26]

    Schuckert, E

    A. Schuckert, E. Crane, A. V. Gorshkov, M. Hafezi, and M. J. Gullans, Fault-tolerant fermionic quan- tum computing, arXiv preprint arXiv:2411.08955 10.48550/arXiv.2411.08955 (2024)

  26. [27]

    Fukui, T

    K. Fukui, T. Matsuura, and N. C. Menicucci, Efficient 15 concatenated bosonic code for additive gaussian noise, Phys. Rev. Lett.131, 170603 (2023)

  27. [28]

    Chamberland, K

    C. Chamberland, K. Noh, P. Arrangoiz-Arriola, E. T. Campbell, C. T. Hann, J. Iverson, H. Putterman, T. C. Bohdanowicz, S. T. Flammia,et al., Building a fault-tolerant quantum computer using concatenated cat codes, PRX Quantum3, 010329 (2022)

  28. [29]

    Steane, Multiple-particle interference and quantum er- ror correction, Proc

    A. Steane, Multiple-particle interference and quantum er- ror correction, Proc. R. Soc. A452, 2551 (1996)

  29. [30]

    Kalajdzievski and J

    T. Kalajdzievski and J. M. Arrazola, Exact gate decom- positions for photonic quantum computing, Phys. Rev. A99, 022341 (2019)

  30. [31]

    D. Su, C. Weedbrook, and K. Br´ adler, Correcting fi- nite squeezing errors in continuous-variable cluster states, Phys. Rev. A98, 042304 (2018)

  31. [32]

    Y. Liu, S. Singh, K. C. Smith, E. Crane, J. M. Mar- tyn, A. Eickbusch, A. Schuckert, R. D. Li, J. Sinanan- Singh, M. B. Soley, T. Tsunoda, I. L. Chuang, N. Wiebe, and S. M. Girvin, Hybrid oscillator-qubit quantum pro- cessors: Instruction set architectures, abstract machine models, and applications, PRX Quantum 10.1103/4rf7- 9tfx (2025)

  32. [33]

    J. i. Yoshikawa, Y. Miwa, A. Huck, U. L. Andersen, P. van Loock, and A. Furusawa, Demonstration of a quantum nondemolition sum gate, Phys. Rev. Lett.101, 250501 (2008)

  33. [34]

    Knill and R

    E. Knill and R. Laflamme, Theory of quantum error- correcting codes, Phys. Rev. A55, 900 (1997)

  34. [35]

    Lloyd and J.-J

    S. Lloyd and J.-J. E. Slotine, Analog quantum error cor- rection, Phys. Rev. Lett.80, 4088 (1998)

  35. [36]

    E. T. Hockings, A. C. Doherty, and R. Harper, Scal- able noise characterization of syndrome-extraction cir- cuits with averaged circuit eigenvalue sampling, PRX Quantum6, 010334 (2025)

  36. [37]

    Welsch, W

    D.-G. Welsch, W. Vogel, and T. Opatrn´ y, Homodyne de- tection and quantum state reconstruction, Prog. Opt.39, 63 (1999)

  37. [38]

    Gonz´ alez-Arciniegas, P

    C. Gonz´ alez-Arciniegas, P. Nussenzveig, M. Martinelli, and O. Pfister, Cluster states from gaussian states: Es- sential diagnostic tools for continuous-variable one-way quantum computing, PRX Quantum2, 030343 (2021)

  38. [39]

    B. W. Walshe, B. Q. Baragiola, R. N. Alexander, and N. C. Menicucci, Continuous-variable gate teleportation and bosonic-code error correction, Phys. Rev. A102, 062411 (2020)

  39. [40]

    L. Hu, Y. Ma, W. Cai, X. Mu, Y. Xu, W. Wang, Y. Wu, H. Wang, Y. Song, C. Zou, S. M. Girvin, L.-M. Duan, and L. Sun, Demonstration of quantum error correction and universal gate set on a binomial bosonic logical qubit, Nat. Phys.15, 503 (2019)

  40. [41]

    S. Hao, X. Deng, X. Su, X. Jia, C. Xie, and K. Peng, Gates for one-way quantum computation based on einstein-podolsky-rosen entanglement, Phys. Rev. A89, 032311 (2014)

  41. [42]

    Kalajdzievski and N

    T. Kalajdzievski and N. Quesada, Exact and approxi- mate continuous-variable gate decompositions, Quantum 5, 394 (2021)

  42. [43]

    Walschaers, Non-gaussian quantum states and where to find them, PRX Quantum2, 030204 (2021)

    M. Walschaers, Non-gaussian quantum states and where to find them, PRX Quantum2, 030204 (2021)

  43. [44]

    Wu and Q

    J. Wu and Q. Zhuang, Continuous-variable error correc- tion for general gaussian noises, Phys. Rev. Applied15, 034073 (2021)

  44. [45]

    T. C. Ralph, Quantum error correction of continuous- variable states against gaussian noise, Phys. Rev. A84, 022339 (2011)

  45. [46]

    Jiang, T

    M. Jiang, T. Wu, J. W. Blanchard, G. Feng, X. Peng, and D. Budker, Experimental benchmarking of quantum con- trol in zero-field nuclear magnetic resonance, Sci. Adv.4, eaar6327 (2018)

  46. [47]

    X. Li, J. Wang, Y.-Y. Jiang, G.-M. Xue, X. Cai, J. Zhou, M. Gong, Z.-F. Liu, S.-Y. Zheng, D.-K. Ma, M. Chen, W.-J. Sun, S. Yang, F. Yan, Y.-R. Jin, S.-P. Zhao, X.-F. Ding, and H.-F. Yu, Cosmic-ray-induced correlated errors in superconducting qubit array, Nat. Commun.16, 4677 (2025)

  47. [48]

    Kessy, A

    A. Kessy, A. Lewin, and K. Strimmer, Optimal whitening and decorrelation, Am. Stat.72, 309 (2018)

  48. [49]

    Schnabel, Squeezed states of light and their applica- tions in laser interferometers, Phys

    R. Schnabel, Squeezed states of light and their applica- tions in laser interferometers, Phys. Rep.684, 1 (2017)

  49. [50]

    Conrad, J

    J. Conrad, J. Eisert, and F. Arzani, Gottesman-kitaev- preskill codes: A lattice perspective, Quantum6, 648 (2022)

  50. [51]

    Huang, A

    G. Huang, A. Beccari, N. J. Engelsen, and T. J. Kippen- berg, Room-temperature quantum optomechanics using an ultralow noise cavity, Nature626, 512 (2024)

  51. [52]

    R. J. Epstein, S. Seidelin, D. Leibfried, J. H. Wesenberg, J. J. Bollinger, J. M. Amini, R. B. Blakestad, J. Britton, J. P. Home, D. Lucas, D. Stick, P. K. Ghosh, C. Mon- roe, and D. J. Wineland, Simplified motional heating rate measurements of trapped ions, Phys. Rev. A76, 033411 (2007)

  52. [53]

    N. Ofek, A. Petrenko, R. Heeres, P. Reinhold, Z. Leghtas, B. Vlastakis, Y. Liu, L. Frunzio, S. M. Girvin, L. Jiang, M. Mirrahimi, M. H. Devoret, and R. J. Schoelkopf, Ex- tending the lifetime of a quantum bit with error correc- tion in superconducting circuits, Nature536, 441 (2016)

  53. [54]

    N. Wang, S. Du, W. Liu, X. Wang, Y. Li, and K. Peng, Long-distance continuous-variable quantum key distri- bution with entangled states, Phys. Rev. Applied10, 064028 (2018)

  54. [55]

    Y. Lu, A. Maiti, J. W. O. Garmon, S. Ganjam, Y. Zhang, J. Claes, L. Frunzio, S. M. Girvin, and R. J. Schoelkopf, High-fidelity parametric beamsplitting with a parity- protected converter, Nature Communications14, 5767 (2023)

  55. [56]

    Leghtas, S

    Z. Leghtas, S. Touzard, I. M. Pop, A. Kou, B. Vlastakis, A. Petrenko, K. M. Sliwa, A. Narla, S. Shankar, and M. H. Devoret, Confining the state of light to a quantum manifold by engineered two-photon loss, Science347, 853 (2015)

  56. [57]

    C. C. Bultink, B. Tarasinski, N. Haandbæk, S. Poletto, N. Haider, D. J. Michalak, A. Bruno, and L. DiCarlo, General method for extracting the quantum efficiency of dispersive qubit readout in circuit qed, Applied Physics Letters112, 092601 (2018)

  57. [58]

    H¨ anggli and R

    L. H¨ anggli and R. K¨ onig, Oscillator-to-oscillator codes do not have a threshold, IEEE Transactions on Information Theory68, 1068 (2022)

  58. [59]

    P. C. Encinar, A. Agust´ ı, and C. Sab´ ın, Digital quan- tum simulation of beam splitters and squeezing with ibm quantum computers, Phys. Rev. A104, 052609 (2021)