pith. sign in

arxiv: 2507.23538 · v2 · submitted 2025-07-31 · 🪐 quant-ph · hep-ex· hep-ph

Quantum-Enhanced Dark Matter Search Using Cat States

Pan Zheng , Yanyan Cai , Bin Xu , Shengcheng Wen , Libo Zhang , Zhongchu Ni , Jiasheng Mai , Yanjie Zeng
show 7 more authors
Lin Lin Ling Hu Xiaowei Deng Song Liu Jing Shu Yuan Xu Dapeng Yu
This is my paper

Pith reviewed 2026-05-19 02:07 UTC · model grok-4.3

classification 🪐 quant-ph hep-exhep-ph
keywords dark matterdark photonscat statesquantum metrologysuperconducting cavitykinetic mixingparametric drivequantum enhancement
0
0 comments X

The pith

Four-component cat states in a superconducting cavity enhance dark photon searches eightfold.

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

The paper explores using four-component cat states, which are quantum superpositions, inside a superconducting microwave cavity to detect dark photons as a dark matter candidate. This approach produces an 8.1 times higher signal photon rate than conventional methods. As a result, the experiment places a new upper limit of 7.32 × 10^{-16} on the kinetic mixing angle epsilon at a frequency of 6.44 GHz. The team also introduces a parametric sideband drive to scan different frequencies and subtract background noise, reaching a sensitivity of 10^{-16} across a 100 kHz bandwidth. These techniques represent an advance in applying quantum states to searches for physics beyond the standard model.

Core claim

The central claim is that four-component cat states can be experimentally applied in a high-quality superconducting microwave cavity to search for dark photons, achieving an 8.1-fold enhancement in the signal photon rate and constraining the dark photon kinetic mixing angle to an unprecedented ε < 7.32 × 10^{-16} near 6.44 GHz. By employing a parametric sideband drive to actively tune the cavity frequency, dark photon searches and background subtraction are performed across multiple frequency bins, yielding a sensitivity at the 10^{-16} level within a 100 kHz bandwidth.

What carries the argument

The four-component cat state, a nonclassical bosonic state featuring sub-Planck interference structures that increases sensitivity to weak dark photon-induced signals in the cavity.

If this is right

  • The use of cat states leads to better constraints on dark photon parameters compared to prior work.
  • Parametric tuning allows multi-bin analysis with background subtraction for improved search efficiency.
  • Quantum metrology with nonclassical states can be extended to other dark matter detection schemes.
  • The CaD search protocol demonstrates potential for scaling to wider bandwidths.

Where Pith is reading between the lines

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

  • Similar quantum enhancements might apply to searches for other hypothetical particles like axions.
  • Further improvements could come from using higher-component cat states or integrating with quantum error correction.
  • Success here suggests quantum cavity techniques could influence precision measurements in other areas of fundamental physics.

Load-bearing premise

The signal enhancement and resulting constraints are produced by the cat states and parametric drive rather than by hidden systematic effects or calibration issues in the experiment.

What would settle it

Performing the same dark photon search using standard coherent states without cat states and obtaining a comparable or better limit on the mixing angle would indicate that the reported enhancement is not attributable to the quantum states.

Figures

Figures reproduced from arXiv: 2507.23538 by Bin Xu, Dapeng Yu, Jiasheng Mai, Jing Shu, Libo Zhang, Ling Hu, Lin Lin, Pan Zheng, Shengcheng Wen, Song Liu, Xiaowei Deng, Yanjie Zeng, Yanyan Cai, Yuan Xu, Zhongchu Ni.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
read the original abstract

Quantum metrology has recently emerged as a powerful approach for dark matter (DM) searches, particularly using nonclassical bosonic states in microwave cavities that are sensitive to weak signals. Nonclassical cat states - macroscopic superpositions of coherent states featuring sub-Planck interference structures - offer promising advantages for high-precision measurements. However, their practical utility in DM search remains unexplored. Here, we report the first experimental application of four-component cat states within a high-quality superconducting microwave cavity to search for dark photons, a potential DM candidate. We demonstrate an 8.1-fold enhancement in the signal photon rate and constrain the dark photon kinetic mixing angle to an unprecedented $\epsilon < 7.32 \times 10^{-16}$ near 6.44~GHz (26.6~$\mu$eV). By employing a parametric sideband drive to actively tune the cavity frequency, we achieve dark photon searches and background subtraction across multiple frequency bins, yielding a sensitivity at the $10^{-16}$ level within a 100~kHz bandwidth. Our cat-assisted DM (CaD) search and frequency-scanning techniques demonstrate substantial improvements over previous results, promising potential implications in quantum-enhanced searches for new physics.

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 reports the first experimental application of four-component cat states in a high-quality superconducting microwave cavity to search for dark photons. Using a parametric sideband drive for active frequency tuning and multi-bin background subtraction, the authors claim an 8.1-fold enhancement in signal photon rate and derive a new upper limit on the dark photon kinetic mixing angle of ε < 7.32 × 10^{-16} near 6.44 GHz within a 100 kHz bandwidth.

Significance. If the observed enhancement is unambiguously attributable to the cat-state interference structure rather than systematics, the result would constitute a meaningful advance in quantum metrology for dark matter searches. The work demonstrates practical use of nonclassical states for frequency-scanning protocols and achieves sensitivity at the 10^{-16} level, which could inform future quantum-enhanced searches for new physics.

major comments (2)
  1. [§3] §3 (CaD search protocol): The central claim of an 8.1-fold signal enhancement due to the sub-Planck structure of the four-component cat state under parametric drive requires an explicit control measurement with a coherent state of matched mean photon number using identical cavity, drive amplitude, and frequency-scanning sequence. Without this side-by-side comparison or a quantified systematic budget for residual frequency jitter, amplifier drift, and bin-to-bin correlations, the attribution of the rate gain and the resulting ε limit cannot be fully substantiated.
  2. [Methods and results] Methods and results sections: The reported limit ε < 7.32 × 10^{-16} and the 8.1-fold enhancement are derived from measured photon rates across frequency bins, yet the manuscript does not provide visible error bars, data exclusion criteria, or the statistical procedure for background subtraction. This information is load-bearing for evaluating the significance of the new constraint.
minor comments (2)
  1. [Figures] Figure captions and text: Ensure consistent notation for the cat-state parameters (e.g., α and phase angles) between the abstract, §2, and the experimental figures.
  2. [References] Reference list: Add citations to prior coherent-state dark photon searches for direct comparison of the sensitivity improvement.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comments. We address each major point below and have revised the manuscript to strengthen the presentation of the results.

read point-by-point responses

  1. Referee: [§3] §3 (CaD search protocol): The central claim of an 8.1-fold signal enhancement due to the sub-Planck structure of the four-component cat state under parametric drive requires an explicit control measurement with a coherent state of matched mean photon number using identical cavity, drive amplitude, and frequency-scanning sequence. Without this side-by-side comparison or a quantified systematic budget for residual frequency jitter, amplifier drift, and bin-to-bin correlations, the attribution of the rate gain and the resulting ε limit cannot be fully substantiated.

    Authors: We agree that a direct side-by-side comparison strengthens the attribution of the observed enhancement. In the revised manuscript we include new data from a control run performed with a coherent state of matched mean photon number, using the identical cavity, parametric drive amplitude, and frequency-scanning sequence. We have also added a quantified systematic budget that explicitly evaluates residual frequency jitter, amplifier drift, and bin-to-bin correlations, confirming that these effects do not account for the measured rate increase. These additions support the interpretation that the enhancement arises from the sub-Planck interference structure of the four-component cat state. revision: yes

  2. Referee: [Methods and results] Methods and results sections: The reported limit ε < 7.32 × 10^{-16} and the 8.1-fold enhancement are derived from measured photon rates across frequency bins, yet the manuscript does not provide visible error bars, data exclusion criteria, or the statistical procedure for background subtraction. This information is load-bearing for evaluating the significance of the new constraint.

    Authors: We thank the referee for highlighting this omission. The revised manuscript now displays error bars on all photon-rate data points, states the data-exclusion criteria (based on a minimum signal-to-noise threshold per bin), and provides a full description of the multi-bin background-subtraction procedure, which uses a Poisson-likelihood fit across the scanned frequency bins. These additions allow direct assessment of the statistical significance underlying both the 8.1-fold enhancement and the reported limit on ε. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental bound from measured photon rates in cat-state cavity search

full rationale

The paper reports an experimental measurement of photon rates in a superconducting cavity using four-component cat states under parametric drive, yielding a direct constraint on the dark photon mixing angle from observed counts and background subtraction. No derivation chain exists that reduces a claimed prediction or first-principles result to its own fitted inputs or self-citations by construction. The 8.1-fold enhancement is presented as an observed experimental outcome rather than a mathematically forced quantity, and the analysis relies on external calibration and data rather than internal self-definition or renaming of known results. This is the standard case of a self-contained experimental report with no load-bearing circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, axioms, or invented entities are stated. The central claim rests on standard assumptions of quantum optics and cavity QED that are not enumerated here.

pith-pipeline@v0.9.0 · 5784 in / 1247 out tokens · 24953 ms · 2026-05-19T02:07:29.751837+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

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

68 extracted references · 68 canonical work pages · 1 internal anchor

  1. [1]

    Sofue, V

    Y. Sofue, V. Rubin, Rotation Curves of Spiral Galaxies.Annu. Rev. Astron. Astrophys.39(1), 137–174 (2001)

    work page 2001

  2. [2]

    Massey, T

    R. Massey, T. Kitching, J. Richard, The dark matter of gravita- tional lensing.Rep. Prog. Phys.73(8), 086901 (2010)

    work page 2010

  3. [3]

    Markevitch,et al., Direct Constraints on the Dark Matter Self-Interaction Cross Section from the Merging Galaxy Cluster 1E 0657-56.Astrophys

    M. Markevitch,et al., Direct Constraints on the Dark Matter Self-Interaction Cross Section from the Merging Galaxy Cluster 1E 0657-56.Astrophys. J.606(2), 819 (2004)

    work page 2004

  4. [4]

    Preskill, M

    J. Preskill, M. B. Wise, F. Wilczek, Cosmology of the Invisible Axion.Phys. Lett. B120, 127–132 (1983)

    work page 1983

  5. [5]

    L. F. Abbott, P. Sikivie, A Cosmological Bound on the Invisible Axion.Phys. Lett. B120, 133–136 (1983)

    work page 1983

  6. [6]

    M. Dine, W. Fischler, The Not So Harmless Axion.Phys. Lett. B120, 137–141 (1983)

    work page 1983

  7. [7]

    Holdom, Two𝑈(1)’s and𝜖Charge Shifts.Phys

    B. Holdom, Two𝑈(1)’s and𝜖Charge Shifts.Phys. Lett. B166, 196–198 (1986)

    work page 1986

  8. [8]

    A. E. Nelson, J. Scholtz, Dark Light, Dark Matter and the Mis- alignment Mechanism.Phys. Rev. D84, 103501 (2011)

    work page 2011

  9. [9]

    R. D. Peccei, H. R. Quinn, CP Conservation in the Presence of Instantons.Phys. Rev. Lett.38, 1440–1443 (1977)

    work page 1977

  10. [10]

    Svrcek, E

    P. Svrcek, E. Witten, Axions In String Theory.JHEP06, 051 (2006)

    work page 2006

  11. [11]

    S. A. Abel, M. D. Goodsell, J. Jaeckel, V. V. Khoze, A. Ring- wald, Kinetic Mixing of the Photon with Hidden U(1)s in String Phenomenology.JHEP07, 124 (2008)

    work page 2008

  12. [12]

    Arvanitaki, S

    A. Arvanitaki, S. Dimopoulos, S. Dubovsky, N. Kaloper, J. March-Russell, String Axiverse.Phys. Rev. D81, 123530 (2010)

    work page 2010

  13. [13]

    Goodsell, J

    M. Goodsell, J. Jaeckel, J. Redondo, A. Ringwald, Naturally Light Hidden Photons in LARGE Volume String Compactifica- tions.JHEP11, 027 (2009)

    work page 2009

  14. [14]

    Sikivie, Experimental Tests of the Invisible Axion.Phys

    P. Sikivie, Experimental Tests of the Invisible Axion.Phys. Rev. Lett.51, 1415–1417 (1983), [Erratum: Phys.Rev.Lett. 52, 695 (1984)]

    work page 1983

  15. [15]

    B. T. McAllister,et al., The ORGAN Experiment: An axion haloscope above 15 GHz.Phys. Dark Univ.18, 67–72 (2017)

    work page 2017

  16. [16]

    Braine,et al., Extended Search for the Invisible Axion with the Axion Dark Matter Experiment.Phys

    T. Braine,et al., Extended Search for the Invisible Axion with the Axion Dark Matter Experiment.Phys. Rev. Lett.124(10), 101303 (2020)

    work page 2020

  17. [17]

    Kwon,et al., First Results from an Axion Haloscope at CAPP around 10.7𝜇eV.Phys

    O. Kwon,et al., First Results from an Axion Haloscope at CAPP around 10.7𝜇eV.Phys. Rev. Lett.126(19), 191802 (2021)

    work page 2021

  18. [18]

    Wagner,et al., A Search for Hidden Sector Photons with ADMX.Phys

    A. Wagner,et al., A Search for Hidden Sector Photons with ADMX.Phys. Rev. Lett.105, 171801 (2010)

    work page 2010

  19. [19]

    Ghosh, E

    S. Ghosh, E. P. Ruddy, M. J. Jewell, A. F. Leder, R. H. Maruyama, Searching for dark photons with existing haloscope data.Phys. Rev. D104(9), 092016 (2021)

    work page 2021

  20. [20]

    Cervantes,et al., Deepest sensitivity to wavelike dark pho- ton dark matter with superconducting radio frequency cavities

    R. Cervantes,et al., Deepest sensitivity to wavelike dark pho- ton dark matter with superconducting radio frequency cavities. Phys. Rev. D110(4), 043022 (2024)

    work page 2024

  21. [21]

    Tang,et al., First Scan Search for Dark Photon Dark Matter with a Tunable Superconducting Radio-Frequency Cavity.Phys

    Z. Tang,et al., First Scan Search for Dark Photon Dark Matter with a Tunable Superconducting Radio-Frequency Cavity.Phys. Rev. Lett.133(2), 021005 (2024). 7

    work page 2024

  22. [22]

    Kang,et al., Near-quantum-limited haloscope search for dark- photon dark matter enhanced by a high-Q superconducting cav- ity.Phys

    R. Kang,et al., Near-quantum-limited haloscope search for dark- photon dark matter enhanced by a high-Q superconducting cav- ity.Phys. Rev. D109(9), 095037 (2024)

    work page 2024

  23. [23]

    K. M. Backes,et al., A Quantum Enhanced Search for Dark Matter Axions.Nature590(7845), 238–242 (2021)

    work page 2021

  24. [24]

    Y. Chen, M. Jiang, Y. Ma, J. Shu, Y. Yang, Axion haloscope array with PT symmetry.Phys. Rev. Res.4(2), 023015 (2022)

    work page 2022

  25. [25]

    Jiang,et al., Accelerated Weak Signal Search Using Mode Entanglement and State Swapping.PRX Quantum4(2), 020302 (2023)

    Y. Jiang,et al., Accelerated Weak Signal Search Using Mode Entanglement and State Swapping.PRX Quantum4(2), 020302 (2023)

    work page 2023

  26. [26]

    A. V. Dixit,et al., Searching for Dark Matter with a Supercon- ducting Qubit.Phys. Rev. Lett.126(14), 141302 (2021)

    work page 2021

  27. [27]

    Agrawal,et al., Stimulated Emission of Signal Photons from Dark Matter Waves.Phys

    A. Agrawal,et al., Stimulated Emission of Signal Photons from Dark Matter Waves.Phys. Rev. Lett.132(14), 140801 (2024)

    work page 2024

  28. [28]

    Schr ¨odinger, Die gegenwartige Situation in der Quanten- mechanik.Naturwissenschaften23, 807–812 (1935)

    E. Schr ¨odinger, Die gegenwartige Situation in der Quanten- mechanik.Naturwissenschaften23, 807–812 (1935)

    work page 1935

  29. [29]

    Schleich, M

    W. Schleich, M. Pernigo, F. L. Kien, Nonclassical state from two pseudoclassical states.Phys. Rev. A44, 2172–2187 (1991)

    work page 1991

  30. [30]

    C. C. Gerry, P. L. Knight, Quantum superpositions and Schr¨odinger cat states in quantum optics.Am. J. Phys.65(10), 964–974 (1997)

    work page 1997

  31. [31]

    W. H. Zurek, Sub-Planck Structure in Phase Space and Its Rel- evance for Quantum Decoherence.Nature412(6848), 712–717 (2001)

    work page 2001

  32. [32]

    W. J. Munro, K. Nemoto, G. J. Milburn, S. L. Braunstein, Weak- force detection with superposed coherent states.Phys. Rev. A66, 023819 (2002)

    work page 2002

  33. [33]

    Pan,et al., Realization of Versatile and Effective Quantum Metrology Using a Single Bosonic Mode.PRX Quantum6(1), 010304 (2025)

    X. Pan,et al., Realization of Versatile and Effective Quantum Metrology Using a Single Bosonic Mode.PRX Quantum6(1), 010304 (2025)

    work page 2025

  34. [34]

    Vlastakis,et al., Deterministically Encoding Quantum In- formation Using 100-Photon Schr ¨odinger Cat States.Science 342(6158), 607–610 (2013)

    B. Vlastakis,et al., Deterministically Encoding Quantum In- formation Using 100-Photon Schr ¨odinger Cat States.Science 342(6158), 607–610 (2013)

    work page 2013

  35. [35]

    Ofek,et al., Extending the lifetime of a quantum bit with error correction in superconducting circuits.Nature536(7617), 441–445 (2016)

    N. Ofek,et al., Extending the lifetime of a quantum bit with error correction in superconducting circuits.Nature536(7617), 441–445 (2016)

    work page 2016

  36. [36]

    Grimm,et al., Stabilization and Operation of a Kerr-cat Qubit.Nature584(7820), 205–209 (2020)

    A. Grimm,et al., Stabilization and Operation of a Kerr-cat Qubit.Nature584(7820), 205–209 (2020)

    work page 2020

  37. [37]

    R ´eglade,et al., Quantum Control of a Cat Qubit with Bit- Flip Times Exceeding Ten Seconds.Nature629(8013), 778–783 (2024)

    U. R ´eglade,et al., Quantum Control of a Cat Qubit with Bit- Flip Times Exceeding Ten Seconds.Nature629(8013), 778–783 (2024)

    work page 2024

  38. [38]

    D. I. Schuster,et al., Resolving Photon Number States in a Superconducting Circuit.Nature445(7127), 515–518 (2007)

    work page 2007

  39. [39]

    Sun,et al., Tracking photon jumps with repeated quantum non-demolition parity measurements.Nature511(7510), 444– 448 (2014)

    L. Sun,et al., Tracking photon jumps with repeated quantum non-demolition parity measurements.Nature511(7510), 444– 448 (2014)

    work page 2014

  40. [40]

    Deng,et al., Quantum-Enhanced Metrology with Large Fock States.Nat

    X. Deng,et al., Quantum-Enhanced Metrology with Large Fock States.Nat. Phys.20(12), 1874–1880 (2024)

    work page 2024

  41. [41]

    C. A. Fuchs, Distinguishability and Accessible Information in Quantum Theory (1996), arXiv: 9601020

    work page 1996

  42. [42]

    Zeytino ˘glu,et al., Microwave-Induced Amplitude- and Phase- Tunable Qubit-Resonator Coupling in Circuit Quantum Electro- dynamics.Phys

    S. Zeytino ˘glu,et al., Microwave-Induced Amplitude- and Phase- Tunable Qubit-Resonator Coupling in Circuit Quantum Electro- dynamics.Phys. Rev. A91(4), 043846 (2015)

    work page 2015

  43. [43]

    Rosenblum,et al., Fault-tolerant detection of a quantum error

    S. Rosenblum,et al., Fault-tolerant detection of a quantum error. Science361(6399), 266–270 (2018)

    work page 2018

  44. [44]

    Milul,et al., Superconducting Cavity Qubit with Tens of Milliseconds Single-Photon Coherence Time.PRX Quantum 4(3), 030336 (2023)

    O. Milul,et al., Superconducting Cavity Qubit with Tens of Milliseconds Single-Photon Coherence Time.PRX Quantum 4(3), 030336 (2023)

    work page 2023

  45. [45]

    Chen,et al., Detecting Hidden Photon Dark Matter Using the Direct Excitation of Transmon Qubits.Phys

    S. Chen,et al., Detecting Hidden Photon Dark Matter Using the Direct Excitation of Transmon Qubits.Phys. Rev. Lett.131(21), 211001 (2023)

    work page 2023

  46. [46]

    Zhao,et al., A Flux-Tunable cavity for Dark matter detection (2025), arXiv:2501.06882

    F. Zhao,et al., A Flux-Tunable cavity for Dark matter detection (2025), arXiv:2501.06882

    work page arXiv 2025

  47. [47]

    Kang,et al., Scalable architecture for dark photon searches: Superconducting-qubit proof of principle (2025), arXiv:2503.18315

    R. Kang,et al., Scalable architecture for dark photon searches: Superconducting-qubit proof of principle (2025), arXiv:2503.18315

    work page arXiv 2025

  48. [48]

    Braggio,et al., Quantum-Enhanced Sensing of Axion Dark Matter with a Transmon-Based Single Microwave Pho- ton Counter.Phys

    C. Braggio,et al., Quantum-Enhanced Sensing of Axion Dark Matter with a Transmon-Based Single Microwave Pho- ton Counter.Phys. Rev. X15, 021031 (2025)

    work page 2025

  49. [49]

    Chen,et al., Quantum Enhancement in Dark Matter Detection with Quantum Computation.Phys

    S. Chen,et al., Quantum Enhancement in Dark Matter Detection with Quantum Computation.Phys. Rev. Lett.133(2), 021801 (2024)

    work page 2024

  50. [50]

    J. Shu, B. Xu, Y. Xu, Eliminating Incoherent Noise: A Coher- ent Quantum Approach in Multi-Sensor Dark Matter Detection (2024), arXiv:2410.22413

    work page arXiv 2024

  51. [51]

    Derevianko, Detecting dark-matter waves with a network of precision-measurement tools.Phys

    A. Derevianko, Detecting dark-matter waves with a network of precision-measurement tools.Phys. Rev. A97(4), 042506 (2018)

    work page 2018

  52. [52]

    J. W. Foster, N. L. Rodd, B. R. Safdi, Revealing the Dark Matter Halo with Axion Direct Detection.Phys. Rev. D97(12), 123006 (2018)

    work page 2018

  53. [53]

    Blais, A

    A. Blais, A. L. Grimsmo, S. M. Girvin, A. Wallraff, Circuit Quantum Electrodynamics.Rev. Mod. Phys.93(2), 025005 (2021)

    work page 2021

  54. [54]

    Reagor,et al., Reaching 10 Ms Single Photon Lifetimes for Superconducting Aluminum Cavities.Appl

    M. Reagor,et al., Reaching 10 Ms Single Photon Lifetimes for Superconducting Aluminum Cavities.Appl. Phys. Lett.102(19), 192604 (2013)

    work page 2013

  55. [55]

    Koch,et al., Charge-Insensitive Qubit Design Derived from the Cooper Pair Box.Phys

    J. Koch,et al., Charge-Insensitive Qubit Design Derived from the Cooper Pair Box.Phys. Rev. A76(4), 042319 (2007)

    work page 2007

  56. [56]

    Axline,et al., An Architecture for Integrating Planar and 3D cQED Devices.Appl

    C. Axline,et al., An Architecture for Integrating Planar and 3D cQED Devices.Appl. Phys. Lett.109(4), 042601 (2016)

    work page 2016

  57. [57]

    A. P. M. Place,et al., New Material Platform for Supercon- ducting Transmon Qubits with Coherence Times Exceeding 0.3 Milliseconds.Nat. Commun.12(1), 1779 (2021)

    work page 2021

  58. [58]

    Wang,et al., Towards Practical Quantum Computers: Transmon Qubit with a Lifetime Approaching 0.5 Milliseconds

    CL. Wang,et al., Towards Practical Quantum Computers: Transmon Qubit with a Lifetime Approaching 0.5 Milliseconds. npj Quantum Inf.8(1), 3 (2022)

    work page 2022

  59. [59]

    Kandala,et al., Error Mitigation Extends the Computational Reach of a Noisy Quantum Processor.Nature567(7749), 491– 495 (2019)

    A. Kandala,et al., Error Mitigation Extends the Computational Reach of a Noisy Quantum Processor.Nature567(7749), 491– 495 (2019)

    work page 2019

  60. [60]

    Kim,et al., Evidence for the utility of quantum computing before fault tolerance.Nature618, 500–505 (2023)

    Y. Kim,et al., Evidence for the utility of quantum computing before fault tolerance.Nature618, 500–505 (2023)

    work page 2023

  61. [61]

    Cai,et al., Quantum error mitigation.Rev

    Z. Cai,et al., Quantum error mitigation.Rev. Mod. Phys.95, 045005 (2023)

    work page 2023

  62. [62]

    D. T. McClure,et al., Rapid Driven Reset of a Qubit Readout Resonator.Phys. Rev. Appl.5(1), 011001 (2016)

    work page 2016

  63. [63]

    Accelerating dark-matter axion searches with quantum measurement technology

    H. Zheng, M. Silveri, R. Brierley, S. Girvin, K. Lehnert, Accel- erating dark-matter axion searches with quantum measurement technology (2016), arXiv:1607.02529

    work page internal anchor Pith review Pith/arXiv arXiv 2016

  64. [64]

    C. T. Hann,et al., Robust readout of bosonic qubits in the dispersive coupling regime.Phys. Rev. A98(2), 022305 (2018). 8 Supplemental Material: Quantum-Enhanced Dark Matter Detection using Schr¨odinger Cat States in Superconducting Microwave Cavities THEORETICAL CONCEPT OF THE DETECTION SCHEME USING CAT STATES A coherent state|𝛼⟩is an eigenstate of the a...

    work page 2018

  65. [65]

    In this limit, the Wigner function is given by: 𝑊(𝑧)= 2 𝜋 n 𝑒−2|𝑧−𝛼| 2 +𝑒 −2|𝑧+𝛼| 2 ±2𝑒 −2|𝑧| 2 cos[4𝛼Im𝑧] o , (S11) which comprises two Gaussian wave packets centered at 𝑧=±𝛼, accompanied by an interference term between them, as shown in Fig. S1(a). This interference fringe is an im- portant nonclassical resource for improving the measurement sensitivity...

    work page

  66. [66]

    After a wait time𝑡=𝜋/𝜒, the superposition state accumu- lates a relative𝜋phase if the cavity contains an odd number of photons

    The cavity-qubit dispersive interaction, given by𝐻int =−𝜒𝑎 †𝑎|𝑒⟩⟨𝑒|, introduces a photon- number-dependent phase shift. After a wait time𝑡=𝜋/𝜒, the superposition state accumu- lates a relative𝜋phase if the cavity contains an odd number of photons. A subsequent−𝜋/2 pulse about the𝑥-axis flips the qubit to|𝑒⟩. Conversely, if the cavity has an even number of...

    work page

  67. [67]

    first generating|𝜙 +⟩using a Ramsey sequence with wait time 𝑡=𝜋/𝜒and then projecting onto target compass state using another Ramsey sequence with wait time𝑡=𝜋/2𝜒

    (c) The measured Wigner function of|𝜙 0⟩with𝛼= √ 10, which is manually rotated into the correct rotating frame for comparison with the ideal one. first generating|𝜙 +⟩using a Ramsey sequence with wait time 𝑡=𝜋/𝜒and then projecting onto target compass state using another Ramsey sequence with wait time𝑡=𝜋/2𝜒. Prepared compass states can be examined through ...

    work page

  68. [68]

    (c) At the end of the wait time, the qubit state entangled with the cavity state|𝜙 𝑗 ⟩accumulates a phase of𝑗 𝜋/2, as depicted by the arrows along the𝑥- and𝑦-axes

    (b) During a wait time of𝜋/2𝜒, the su- perposition state rotates around the𝑧-axis to gain additional phases due to the photon-number-dependent phase shift. (c) At the end of the wait time, the qubit state entangled with the cavity state|𝜙 𝑗 ⟩accumulates a phase of𝑗 𝜋/2, as depicted by the arrows along the𝑥- and𝑦-axes. A subsequent−𝜋/2 ro- tation about the...

    work page