pith. sign in

arxiv: 2606.22080 · v2 · pith:XVSACPUVnew · submitted 2026-06-20 · 🪐 quant-ph

Optimizing Pump Conditions of Parametric Amplifiers for Fast Multiplexed Readout of Superconducting Qubits

Jeongwon Kim , Wei Dai , Omrie Ovdat , Akiva Feintuch , Nir Alfasi , Yonuk Chong This is my paper

Pith reviewed 2026-06-26 11:49 UTC · model grok-4.3

classification 🪐 quant-ph
keywords parametric amplifiermultiplexed readoutsuperconducting qubitspump optimizationsignal-to-noise ratiotraveling-wave parametric amplifierreadout time
0
0 comments X

The pith

Maximizing SNR improvement at the limiting qubit's frequency minimizes total multiplexed readout time.

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

The paper establishes that multiplexed readout time for superconducting qubits is governed by the single qubit needing the longest integration to reach a target signal-to-noise ratio. Selecting the parametric amplifier's pump condition to maximize SNR gain specifically at that qubit's readout frequency, instead of averaging gains across all frequencies, shortens the common readout window. The authors demonstrate the approach on a five-qubit chain using a traveling-wave parametric amplifier and report a 320 ns reduction relative to average-SNR optimization while meeting the SNR target for every qubit. A reader would care because the resulting shorter readout window directly increases the number of operations possible before qubit coherence is lost.

Core claim

Choosing the amplifier pump to maximize the signal-to-noise ratio improvement at the readout frequency of the limiting qubit—the qubit that requires the longest readout time to reach a target SNR—minimizes the total multiplexed readout time. This is shown experimentally on a five-qubit multiplexed readout chain with a traveling-wave parametric amplifier, where the strategy reduces readout time by 320 ns compared with optimizing the average SNR improvement across all qubits, without degrading the target SNR for any qubit.

What carries the argument

The limiting qubit, defined as the one whose readout frequency demands the longest integration time to reach target SNR; the pump condition is chosen to maximize SNR improvement at that specific frequency.

If this is right

  • The total multiplexed readout time is set by the worst-performing qubit rather than by an average across the set.
  • Pump calibration must be performed at the frequency of the current limiting qubit rather than at a representative or average frequency.
  • The demonstrated 320 ns saving is achieved while every qubit still meets its individual target SNR.
  • The ordering of qubit readout times follows directly from the measured frequency-dependent SNR improvement curve of the amplifier.

Where Pith is reading between the lines

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

  • If pump settings alter saturation behavior differently at each frequency, the identity of the limiting qubit could shift and require re-identification after each change.
  • Pre-allocating readout frequencies to reduce the spread in required integration times could compound the time saving obtained from pump optimization.
  • In larger arrays the same principle would identify a new limiting qubit after each frequency or power change, suggesting an iterative calibration loop.

Load-bearing premise

That SNR improvement at one chosen frequency is the dominant factor setting the ordering of required readout times and that no other effects such as saturation or crosstalk will reorder the qubits.

What would settle it

An experiment in which the pump chosen for the original limiting qubit causes a different qubit to become the new limiting one or fails to reduce the measured total time needed to reach target SNR on all qubits.

Figures

Figures reproduced from arXiv: 2606.22080 by Akiva Feintuch, Jeongwon Kim, Nir Alfasi, Omrie Ovdat, Wei Dai, Yonuk Chong.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic of multiplexed readout pulses for five qubits. All [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Effect of TWPA pump conditions on readout performance. (a) TWPA gain profiles under two different pump conditions: pump [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: We compute the average ∆SNR across qubits by con￾verting each qubit’s ∆SNR from dB to linear units, averag￾ing in linear units, and converting back to dB, since dB is a logarithmic scale and therefore cannot be averaged by di￾rectly summing dB values and dividing by the number of qubits. Among the feasible pump conditions, we select (i) the operating point that maximizes the average ∆SNR across qubits (ave… view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Readout time required to reach SNR [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Simplified schematic of the measurement setup used for [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Estimated readout infidelity, 1 [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
read the original abstract

Low-noise parametric amplifiers are widely used as the first-stage amplifier in qubit readout chains. The performance of parametric amplifiers depends sensitively on the choice of the pump condition. We propose a strategy for determining the pump condition that is tailored for fast multiplexed readout. Choosing the amplifier pump to maximize the signal-to-noise ratio (SNR) improvement at the readout frequency of the limiting qubit--the qubit that requires the longest readout time to reach a target SNR--minimizes the total multiplexed readout time. We demonstrate our pump calibration strategy experimentally on a five-qubit multiplexed readout chain with a traveling-wave parametric amplifier. Using our strategy, we reduce the multiplexed readout time by 320 ns compared to optimizing the average SNR improvement on all qubits, without degrading the target SNR for any qubit.

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

1 major / 2 minor

Summary. The manuscript claims that for multiplexed readout of superconducting qubits using a traveling-wave parametric amplifier, the optimal pump condition is found by maximizing the SNR improvement specifically at the readout frequency of the limiting qubit (the qubit requiring the longest integration time to reach a target SNR). This choice minimizes the total multiplexed readout time. The claim is supported by an experimental demonstration on a five-qubit chain, where the proposed strategy yields a 320 ns reduction in readout time relative to optimization based on average SNR improvement across all qubits, while still meeting the target SNR on every qubit.

Significance. If the central experimental result holds, the work supplies a practical, hardware-agnostic calibration procedure that directly shortens the readout bottleneck in multiplexed superconducting qubit systems. This is relevant for scaling quantum processors, as faster readout reduces the overhead in quantum error correction cycles and algorithm execution. The approach is notable for being an empirical optimization that measures the time reduction directly rather than relying on fitted models.

major comments (1)
  1. [Experimental demonstration] Experimental demonstration (results section): the reported 320 ns reduction is presented without error bars, uncertainty quantification, or explicit controls confirming that frequency-dependent saturation, crosstalk, or pump-induced heating do not reorder the qubit readout times; these omissions are load-bearing because the central claim rests on the measured time improvement being attributable solely to the limiting-qubit SNR optimization.
minor comments (2)
  1. [Methods] The procedure for identifying the limiting qubit (i.e., how readout times are computed from SNR curves) should be stated explicitly, including any threshold or fitting method used.
  2. Figure captions and axis labels would benefit from indicating the target SNR value and the integration-time axis units for clarity.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their positive assessment of the work and recommendation for minor revision. We address the single major comment below.

read point-by-point responses

  1. Referee: Experimental demonstration (results section): the reported 320 ns reduction is presented without error bars, uncertainty quantification, or explicit controls confirming that frequency-dependent saturation, crosstalk, or pump-induced heating do not reorder the qubit readout times; these omissions are load-bearing because the central claim rests on the measured time improvement being attributable solely to the limiting-qubit SNR optimization.

    Authors: We agree that the presentation would be strengthened by explicit uncertainty quantification and controls for the listed effects. In the revised manuscript we will add error bars obtained from repeated measurements of the multiplexed readout times and include additional data or discussion (in the main text or supplement) confirming that frequency-dependent saturation, crosstalk, and pump-induced heating do not reorder the qubit readout times under the reported pump conditions. This will directly support attribution of the 320 ns reduction to the limiting-qubit SNR optimization. revision: yes

Circularity Check

0 steps flagged

No significant circularity; empirical demonstration

full rationale

The paper proposes an experimental pump optimization strategy for multiplexed qubit readout and validates it via direct measurements on a five-qubit chain, reporting a measured 320 ns reduction. No mathematical derivation chain, fitted parameters renamed as predictions, or self-citation load-bearing steps are present in the provided text. The central claim reduces to observed data rather than any self-referential construction.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The paper is an experimental optimization study. No free parameters, axioms, or invented entities are introduced in the abstract; the central claim rests on direct measurement of SNR and readout durations under different pump settings.

pith-pipeline@v0.9.1-grok · 5681 in / 1074 out tokens · 18988 ms · 2026-06-26T11:49:13.255528+00:00 · methodology

discussion (0)

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

Reference graph

Works this paper leans on

43 extracted references · 10 canonical work pages

  1. [1]

    Physical Review Applied , volume=

    Rapid high-fidelity single-shot dispersive readout of superconducting qubits , author=. Physical Review Applied , volume=. 2017 , publisher=

    2017

  2. [2]

    Nature , volume=

    Realizing repeated quantum error correction in a distance-three surface code , author=. Nature , volume=. 2022 , publisher=

    2022

  3. [3]

    Physical Review Applied , volume=

    Rapid high-fidelity multiplexed readout of superconducting qubits , author=. Physical Review Applied , volume=. 2018 , publisher=

    2018

  4. [4]

    Physical Review Applied , volume=

    Fast readout and reset of a superconducting qubit coupled to a resonator with an intrinsic Purcell filter , author=. Physical Review Applied , volume=. 2022 , publisher=

    2022

  5. [5]

    PRX Quantum , volume=

    Fast multiplexed superconducting-qubit readout with intrinsic purcell filtering using a multiconductor transmission line , author=. PRX Quantum , volume=. 2025 , publisher=

    2025

  6. [6]

    IEEE Transactions on Applied Superconductivity , volume=

    Measurable improvement in multi-qubit readout using a kinetic inductance traveling wave parametric amplifier , author=. IEEE Transactions on Applied Superconductivity , volume=. 2025 , publisher=

    2025

  7. [7]

    Applied Physics Letters , volume=

    Single-shot readout of a superconducting flux qubit with a flux-driven Josephson parametric amplifier , author=. Applied Physics Letters , volume=. 2013 , publisher=

    2013

  8. [8]

    Science , volume=

    A near--quantum-limited Josephson traveling-wave parametric amplifier , author=. Science , volume=. 2015 , publisher=

    2015

  9. [9]

    Physical Review X , volume=

    Photonic-crystal Josephson traveling-wave parametric amplifier , author=. Physical Review X , volume=. 2020 , publisher=

    2020

  10. [10]

    arXiv preprint arXiv:2408.16366 , year=

    A small footprint travelling-wave parametric amplifier with a high Signal-to-Noise Ratio improvement in a wide band , author=. arXiv preprint arXiv:2408.16366 , year=

    arXiv

  11. [11]

    Physical Review Applied , volume=

    rf-SQUID-based traveling-wave parametric amplifier with input saturation power of- 84 dBm across more than one octave in bandwidth , author=. Physical Review Applied , volume=. 2025 , publisher=

    2025

  12. [12]

    Applied Physics Letters , volume=

    Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching , author=. Applied Physics Letters , volume=. 2015 , publisher=

    2015

  13. [13]

    Physical review letters , volume=

    Resonant phase matching of Josephson junction traveling wave parametric amplifiers , author=. Physical review letters , volume=. 2014 , publisher=

    2014

  14. [14]

    arXiv preprint arXiv:2507.03642 , year=

    High-power readout of a transmon qubit using a nonlinear coupling , author=. arXiv preprint arXiv:2507.03642 , year=

    arXiv

  15. [15]

    Applied physics reviews , volume=

    A quantum engineer's guide to superconducting qubits , author=. Applied physics reviews , volume=. 2019 , publisher=

    2019

  16. [16]

    EPJ Quantum technology , volume=

    Engineering cryogenic setups for 100-qubit scale superconducting circuit systems , author=. EPJ Quantum technology , volume=. 2019 , publisher=

    2019

  17. [17]

    Physical review letters , volume=

    Heralded state preparation in a superconducting qubit , author=. Physical review letters , volume=. 2012 , publisher=

    2012

  18. [18]

    Physical review letters , volume=

    Initialization by measurement of a superconducting quantum bit circuit , author=. Physical review letters , volume=. 2012 , publisher=

    2012

  19. [19]

    Applied Physics Letters , volume=

    Frequency division multiplexing readout and simultaneous manipulation of an array of flux qubits , author=. Applied Physics Letters , volume=. 2012 , publisher=

    2012

  20. [20]

    Applied Physics Letters , keywords =

    Mutus, J Y and White, T C and Barends, R and Chen, Y and Chen, Z and Chiaro, B and Dunsworth, A and Jeffrey, E and Kelly, J and Megrant, A and Neill, C and O'Malley, P J J and Roushan, P and Sank, D and Vainsencher, A and Wenner, J and Sundqvist, K M and Cleland, A N and Martinis, J M , isbn =. Applied Physics Letters , keywords =

  21. [21]

    Physical review letters , volume=

    Fast accurate state measurement with superconducting qubits , author=. Physical review letters , volume=. 2014 , publisher=

    2014

  22. [22]

    npj Quantum Information , volume=

    Fast and high-fidelity dispersive readout of a spin qubit with squeezed microwave and resonator nonlinearity , author=. npj Quantum Information , volume=. 2024 , publisher=

    2024

  23. [23]

    Reviews of Modern Physics , volume=

    Introduction to quantum noise, measurement, and amplification , author=. Reviews of Modern Physics , volume=. 2010 , publisher=

    2010

  24. [24]

    Nature , volume =

    Deterministic quantum teleportation with feed-forward in a solid state system , author =. Nature , volume =. 2013 , doi =

    2013

  25. [25]

    Science Bulletin , volume =

    Deterministic quantum state and gate teleportation between distant superconducting chips , author =. Science Bulletin , volume =. 2025 , doi =

    2025

  26. [26]

    Nature , volume=

    Extending the lifetime of a quantum bit with error correction in superconducting circuits , author=. Nature , volume=. 2016 , publisher=

    2016

  27. [27]

    Nature , volume=

    Suppressing quantum errors by scaling a surface code logical qubit , author =. Nature , volume=. 2023 , publisher=

    2023

  28. [28]

    Nature , volume=

    Real-time quantum error correction beyond break-even , author=. Nature , volume=. 2023 , publisher=

    2023

  29. [29]

    Nature , volume=

    Beating the break-even point with a discrete-variable-encoded logical qubit , author=. Nature , volume=. 2023 , publisher=

    2023

  30. [30]

    Physical Review B , author =

    Dispersive magnetometry with a quantum limited. Physical Review B , author =. 2011 , pages =. doi:10.1103/PhysRevB.83.134501 , number =

    work page doi:10.1103/physrevb.83.134501 2011

  31. [31]

    Nature , author =

    Phase-preserving amplification near the quantum limit with a. Nature , author =. 2010 , pages =. doi:10.1038/nature09035 , number =

    work page doi:10.1038/nature09035 2010

  32. [32]

    Optimizing the Nonlinearity and Dissipation of a SNAIL Parametric Amplifier for Dynamic Range , author =. Phys. Rev. Appl. , volume =. 2018 , month =. doi:10.1103/PhysRevApplied.10.054020 , url =

    work page doi:10.1103/physrevapplied.10.054020 2018

  33. [33]

    Reflection-enhanced gain in traveling-wave parametric amplifiers , author =. Phys. Rev. B , volume =. 2023 , month =. doi:10.1103/PhysRevB.107.174520 , url =

    work page doi:10.1103/physrevb.107.174520 2023

  34. [34]

    Journal of Physics D: Applied Physics , volume=

    Quantum analysis of second-order effects in superconducting travelling-wave parametric amplifiers , author=. Journal of Physics D: Applied Physics , volume=. 2021 , publisher=

    2021

  35. [35]

    Peripheral circuits for ideal performance of a traveling-wave parametric amplifier , author =. Phys. Rev. Appl. , volume =. 2024 , month =. doi:10.1103/PhysRevApplied.21.064062 , url =

    work page doi:10.1103/physrevapplied.21.064062 2024

  36. [36]

    Applied Physics Letters , volume =

    Readout of a quantum processor with high dynamic range Josephson parametric amplifiers , author =. Applied Physics Letters , volume =. 2023 , doi =

    2023

  37. [37]

    Applied Physics Letters , number =

    Roy, Tanay and Kundu, Suman and Chand, Madhavi and Vadiraj, A M and Ranadive, A and Nehra, N and Patankar, Meghan P and Aumentado, J and Clerk, A A and Vijay, R , doi =. Applied Physics Letters , number =

  38. [38]

    Lumped-element broadband SNAIL parametric amplifier with on-chip pump filter for multiplexed readout , author =. Phys. Rev. Appl. , volume =. 2025 , month =. doi:10.1103/5l86-pw21 , url =

    work page doi:10.1103/5l86-pw21 2025

  39. [39]

    Benchmarking the Readout of a Superconducting Qubit for Repeated Measurements , author =. Phys. Rev. Lett. , volume =. 2025 , month =. doi:10.1103/PhysRevLett.134.100601 , url =

    work page doi:10.1103/physrevlett.134.100601 2025

  40. [40]

    PRX Quantum , volume =

    Floquet-Mode Traveling-Wave Parametric Amplifiers , author =. PRX Quantum , volume =. 2022 , month =. doi:10.1103/PRXQuantum.3.020306 , url =

    work page doi:10.1103/prxquantum.3.020306 2022

  41. [41]

    Applied Physics Letters , volume =

    Broadband merged-element Josephson parametric amplifier , author =. Applied Physics Letters , volume =. 2025 , doi =

    2025

  42. [42]

    Optimizing the pump coupling for a three-wave-mixing Josephson parametric amplifier , author =. Phys. Rev. Appl. , volume =. 2025 , month =. doi:10.1103/PhysRevApplied.23.054069 , url =

    work page doi:10.1103/physrevapplied.23.054069 2025

  43. [43]

    System characterization of dispersive readout in superconducting qubits , author =. Phys. Rev. Appl. , volume =. 2025 , month =. doi:10.1103/PhysRevApplied.23.024055 , url =

    work page doi:10.1103/physrevapplied.23.024055 2025