Space-Time-Coupled Qubits for Enhanced Superconducting Quantum Computing

Sajjad Taravati

REVIEW 5 major objections 4 minor 1 cited by

Space-Time-Coupled Qubits for Enhanced Superconducting Quantum Computing

T0 review · 5 major / 4 minor · reviewed 2026-08-10 · deepseek-v4-flash

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Pith's one-line read The paper claims that a space-time-modulated Josephson metasurface placed over a superconducting qubit array creates polychromatic couplings between every pair of qubits, converting nearest-neighbor connectivity into all-to-all…

desk verdict A genuinely new architecture idea whose central claim—that a driven Josephson metasurface creates coherent all-to-all qubit couplings—is asserted rather than derived; not publishable in current form. read the letter →

arxiv 2501.16872 v3 pith:VZMEOQVD submitted 2025-01-28 quant-ph cond-mat.supr-con

Sajjad Taravati This is my paper · ORCID

classification quant-phcond-mat.supr-con

keywords space-timemodulationJosephsonmetasurfacesuperconductingqubitspolychromaticcouplingall-to-allconnectivitycoherenceenhancementcrosstalkmitigationfrequency-divisionmultiplexing

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper proposes adding a space-time-modulated Josephson metasurface—an engineered superconducting surface whose electrical response varies periodically in both space and time—above a qubit array. The central claim is that the surface acts as a frequency-converting mirror: a photon emitted by one qubit returns at several harmonics of the qubit frequency, so the coupling Hamiltonian gains terms between all pairs of qubits, not just neighbors. If true, quantum processors would no longer need swap chains for long-range gates, and frequency-division multiplexing would separate qubit channels enough to reduce crosstalk and extend coherence. The paper backs this with a detailed classical scattering calculation and full-wave simulations of four- and eight-qubit arrays.

What carries the argument

The central object is the space-time-modulated Josephson metasurface: a thin array of Josephson junctions whose critical current is modulated as $J(z,t)=f_{\mathrm{nl,per}}(\kappa_s z,\omega_s t)$. Its role in the argument is to provide frequency conversion and nonreciprocity: solving the electromagnetic boundary problem at the metasurface gives reflected field harmonics with amplitudes $R_n$, and those $R_n$ are identified with the polychromatic coupling constants $g^{(m)}_{ij,kl}$. Everything else—all-to-all connectivity, gate-depth reduction, coherence extension, and entanglement robustness—is traced back to those harmonic amplitudes and the frequency separation $\Delta f$ they introduce.

What would settle it

Place two non-adjacent qubits at frequencies $\omega_s$ and $2\omega_s$ under the metasurface and drive one qubit; the central claim predicts coherent exchange oscillations between them at the harmonic-coupling strength $g^{(m)}_{ij,kl}$. If those oscillations do not appear, or if either qubit's decoherence exceeds what the classical scattering calculation allows, the central claim would be falsified.

Watch

Extended reading notes

Core claim

The discovery proposed here is that a reflective space-time-periodic Josephson junction array can mediate polychromatic qubit interactions. With critical current density $J(z,t)=f_{\mathrm{nl,per}}(\kappa_s z,\omega_s t)$, the surface turns an incident field at $\omega_0$ into reflected harmonics at $\omega_n=\omega_0+n\omega_s$ with amplitudes $R_n$. The paper takes these classical amplitudes as the quantum coupling strengths $g^{(m)}_{ij,kl}$ in an extended Hamiltonian that sums over all qubit pairs and all harmonics. The resulting architecture claims three quantitative benefits: gate depth drops from $D_m$ to $D_p=D_m/\langle C_{\mathrm{polychromatic}}\rangle$, coherence time becomes $T'_2=T_2(1+2\pi\Delta f/\gamma)$, and entanglement fidelity becomes $F'_{\mathrm{entangled}}=F_{\mathrm{entangled}}\exp(-t/T'_2)$, which exceeds the monochromatic value because $T'_2>T_2$. The simulations show selective excitation of qubits at $2\omega_s$, $3\omega_s$, and $4\omega_s$, and simultaneous excitation of up to eight qubits at harmonics $2\omega_s$ through $8\omega_s$.

Load-bearing premise

The paper assumes that the classical frequency-conversion amplitudes for a microwave field reflecting off the modulated Josephson surface carry over unchanged as coherent couplings between qubits, bringing no extra loss or noise from the same nonlinear surface.

Editorial extensions

If this is right

Non-adjacent qubits in a $4\times 4$ array acquire direct couplings, so two-qubit gates that once required swap chains can be performed in fewer steps, with $\langle C_{\mathrm{polychromatic}}\rangle$ quantifying the connectivity gain.
Because each pair interacts in its own frequency channel, crosstalk from shared resonators and control lines is suppressed, and the coherence time grows as $T'_2=T_2(1+2\pi\Delta f/\gamma)$.
Entanglement fidelity decays with the enhanced $T'_2$, so multi-qubit entangled states survive longer under the same noise environment, reducing the error-correction overhead needed.
State-frequency conversion lets qubits with different operating frequencies interact, opening a route to hybrid superconducting and photonic quantum processors.
Simulations of four- and eight-qubit arrays indicate the scheme extends beyond nearest-neighbor lattices without requiring a different physical qubit layout.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The decisive unstated assumption is that the classical harmonic amplitudes $R_n$ survive quantization as coherent couplings with no added noise; a full circuit-quantum derivation of qubits coupled to the modulated Josephson medium is the missing step before experimental commitment.
The coherence formula predicts a linear dependence of $T'_2$ on frequency separation $\Delta f$; a controlled experiment that varies $\Delta f$ for one fixed qubit pair could test this scaling directly.
The same frequency-conversion mechanism could serve as a general quantum frequency interface between dissimilar qubit platforms, a use the paper mentions but does not develop into a concrete transduction protocol.
If the time-modulated nonlinear medium introduces dissipation such as quasiparticle losses that the classical scattering calculation does not capture, the net coherence benefit could be smaller than claimed; the paper does not quantify such losses.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Short version: this is a proposal, not a demonstrated result. The specific idea is new—coupling superconducting qubits through a space-time-modulated Josephson metasurface does not appear in the cited literature—and the paper correctly identifies connectivity and crosstalk as real bottlenecks. Credit where due: the classical full-wave scattering calculation for the metasurface is a legitimate piece of work, and the figures do show multiple frequency components emerging from a modulated junction array.

The problem is that the central quantum claim is asserted, not derived. Equation (3) writes down a polychromatic exchange Hamiltonian with coupling rates g^(m)_ij,kl tied to the classical scattering coefficients R_n. But a driven, nonlinear superconducting medium does not automatically behave as a coherent beamsplitter when quantized. The R_n amplitudes describe classical frequency conversion; they do not establish that the induced interaction is a σ+σ− exchange, that the relevant sidebands are resonant with the qubit detunings, or what extra noise and dephasing the modulation introduces. The manuscript never performs that translation. It simply posits Eq. (3) and then quotes performance formulas: Eq. (5) for T2', Eq. (6) for noise suppression with a free bandwidth σ, and Eq. (7b) for entanglement fidelity that exponentiates the same assumed T2'. None of these are derived from a master equation or measured data. The enhanced coherence and fidelity are baked into the assumptions. There are no quantitative simulations of T2, fidelity, or crosstalk, and no baseline comparison with a conventional array.

The figures show hand-tuned field patterns, which is fine for illustrating the classical effect, but they do not test the quantum proposal. So the central argument does not hold up as presented. That said, the underlying concept is not obviously wrong. A careful circuit-QED treatment of qubits coupled to a quantized, time-modulated Josephson array could either validate or kill the all-to-all coupling idea. This paper just does not do the work.

Who gets value from it: someone curious about speculative coupling architectures might find the concept worth a skim, but it is not a reliable reference for any quantitative claim. If it crossed my desk, I would not send it to referees in this form. I would return it with a request to derive the coupling rates from a quantized model, provide a noise analysis, and give actual numbers for coherence and fidelity from a master equation.

Referee Report

5 major / 4 minor

Summary. The manuscript proposes that a space-time-modulated cryogenic-compatible Josephson metasurface placed over a superconducting qubit array enables polychromatic, all-to-all qubit couplings described by a multi-frequency Hamiltonian (Eq. 3), and that the resulting frequency separation enhances coherence times (Eq. 5), suppresses noise (Eq. 6), and improves entanglement fidelity (Eq. 7b). The paper presents classical full-wave field patterns for a periodically modulated Josephson junction array and qualitative arguments that these patterns correspond to qubit state transitions. No derivation of the quantum Hamiltonian from a circuit-QED treatment is provided, and the performance formulas are asserted rather than derived from a master equation or measured data.

Significance. If the central claims were established, the proposal could be highly significant for superconducting quantum processors by offering a path from nearest-neighbor to all-to-all connectivity with frequency-multiplexed crosstalk suppression. However, the manuscript does not provide the necessary theoretical or numerical support: the all-to-all Hamiltonian is posited, the coherence-time and fidelity enhancements are assumed formulas, and the results section contains only classical field distributions with no quantitative quantum metrics. The significance is therefore conditional on future work that supplies the missing quantum derivation and validation.

major comments (5)

[Eq. (3) and 'Long-Range and Polychromatic Entanglement'] The central Hamiltonian with polychromatic couplings g^(m)_ij,kl is postulated directly. No derivation connects the classical scattering coefficients R_n of Eq. (9) to the coherent qubit-qubit coupling rates g^(m)_ij,kl in a quantized circuit. A driven, nonlinear, time-dependent Josephson medium can produce classical frequency conversion without necessarily yielding the coherent sigma_+ sigma_- exchange terms assumed in Eq. (3); parametric gain, added noise, and backaction dephasing must be analyzed. Without a circuit-QED derivation, the all-to-all connectivity claim is unsupported.
[Eq. (5), 'Coherence Time Improvement'] The formula T'_2 = T2(1 + 2*pi*Delta_f/gamma) is asserted without a noise model or master-equation derivation. The text explains that frequency separation 'mitigates crosstalk' and 'reduces spectral overlap,' but this is a qualitative argument, not a calculation. The equation assumes the very effect it is meant to prove: that Delta_f reduces the decoherence rate of each qubit. Additionally, the symbol gamma is used earlier for the space-time velocity ratio in the Results section and here as a decoherence rate, which is confusing.
[Eq. (6), 'Robustness Against Crosstalk and Noise'] The noise suppression formula S_eff(omega) = S0(omega) exp(-Delta_omega^2/2*sigma^2) is introduced with an unspecified free bandwidth sigma. No physical mechanism or derivation shows that the metasurface produces a Gaussian attenuation of the environmental noise spectrum. The claim that this 'results in a significant reduction in dephasing noise, improving both T1 and T2' is not backed by any microscopic analysis of the qubit-environment coupling in the presence of the modulated medium.
[Eq. (7b), 'Improved Entanglement Robustness'] The entanglement fidelity formula F'_entangled = F_entangled * exp(-t/T2') is not a valid substitution. If F_entangled already includes the exponential decay exp(-t/T2), then the polychromatic fidelity should replace T2 with T2' in the same exponential, not multiply the old fidelity by a new decay factor. More fundamentally, this expression is not derived from a master equation for the actual qubit-metasurface system; it inherits the unvalidated Eq. (5) and therefore cannot serve as evidence of improved fidelity.
[Results, Figs. 5 and 6] The paper claims 'full-wave simulations and quantum performance analyses,' but the results show only classical field patterns with labels indicating qubit state transitions. There are no quantitative simulations of qubit dynamics, no coherence times, no fidelity curves, and no gate-error estimates. The figures do not support the stated conclusions about 'enhanced coherence times' and 'entanglement fidelity' because those metrics are never computed from the simulated fields or from a quantum model.

minor comments (4)

[Notation throughout] The symbol gamma is used both for the space-time velocity ratio (e.g., Fig. 5) and for the decoherence rate in Eq. (5); please use distinct symbols to avoid ambiguity.
[Eq. (4a)] The relation D_p = D_m / <C_polychromatic> is plausible but is stated without justification; since it is not central to the main claims, this is a minor issue.
[Figs. 5 and 6 captions and axes] Several figure captions and axis labels are garbled (e.g., 'x( 0)' and 'z( 0)' likely mean x/lambda0 and z/lambda0), and caption text such as 'RF: 0.4; DC: 0.97' is incomplete. These should be cleaned up.
[References] The derivation of F(t) = exp(-t/T2) is attributed to general references [35-37] without a detailed noise model; the manuscript would benefit from citing a standard dephasing model that justifies this form for superconducting qubits.

Circularity Check

4 steps flagged · score 7.0 of 10

The coherence and fidelity improvements are introduced by assumed formulas (Eqs. 5-7b) rather than derived from the metasurface, so the headline performance gains are built into the model.

self definitional [Section 'Coherence Time Improvement', Eq. (5)]
"The modified coherence time in the polychromatic case is given by T'_2 = T2(1 + 2π Δf/γ), (5) ... The term Δf/γ reflects how increasing the separation between frequencies proportionally enhances the coherence time."

Eq. (5) is a postulated linear relation, not a result of a noise or crosstalk calculation. Since every positive Δf makes T'_2 > T2, the paper's 'coherence time improvement' is true by definition of the formula. No derivation connects γ or Δf to the metasurface's scattering coefficients, so the enhancement is an input assumption rather than an output of the full-wave simulation.
self definitional [Section 'Robustness Against Crosstalk and Noise', Eq. (6)]
"The effective noise spectral density Seff(ω) decreases as: Seff(ω) = S0(ω) · exp(−Δω^2/(2σ^2)), (6) ... This results in a significant reduction in dephasing noise, improving both T1 and T2."

The paper defines Seff as a Gaussian-narrowed version of S0 with a free bandwidth σ and then treats the narrowing as the metasurface's noise suppression. The 'reduction in dephasing noise' is read directly off the assumed exponential factor; no microscopic derivation from the space-time-modulated Josephson junction is given. The noise robustness claim is therefore contained in the chosen ansatz.

2 more flagged steps

self definitional [Section 'Improved Entanglement Robustness', Eq. (7b)]
"Under Markovian decoherence ... the entanglement fidelity F'_entangled in the polychromatic case reads F'_entangled = F_entangled · exp(−t/T'_2), (7b) ... The exponential fidelity decay slows proportionally to T'_2, ensuring F'_entangled > F_entangled for identical noise conditions."

Eq. (7b) merely substitutes the assumed T'_2 from Eq. (5) into the standard exponential fidelity-decay formula. Because T'_2 was already defined to be larger than T2 for positive Δf, the inequality F'_entangled > F_entangled follows by arithmetic from the input assumption, not from any metasurface-mediated state dynamics. The entanglement-robustness prediction is thus equivalent to the assumed coherence-time formula.
other [Section 'Long-Range and Polychromatic Entanglement Through Space-Time-Coupled Qubit Array', Eq. (3)]
"The Hamiltonian in this case extends to: H = Σ ... Σ_m g^(m)_ij,kl · e^{iΔω^(m)_ij,kl t}(σ^(i,j)_+ σ^(k,l)_− + σ^(i,j)_− σ^(k,l)_+), (3), where g^(m)_ij,kl is the coupling strength at the m-th frequency ... This allows for non-zero g^(m)_ij,kl between qubits separated by larger distances."

The all-to-all polychromatic coupling is asserted by writing Eq. (3) with nonzero g^(m)_ij,kl for arbitrary pairs; it is not derived from the classical scattering coefficients R_n computed later in Eqs. (8)-(9). The full-wave simulation demonstrates classical harmonic generation, but the paper never evaluates g^(m) from R_n or from the circuit-QED degrees of freedom. The central connectivity claim therefore rests on an ansatz whose content is the assumed Hamiltonian, making the 'prediction' of all-to-all connectivity an input rather than a derived result.

full rationale

The paper contains a genuinely independent classical calculation: the space-time-modulated Josephson junction array's reflected harmonics are obtained from boundary conditions (Eqs. 8-9) and shown in Figs. 5-6. That part is self-contained and would support a classical frequency-conversion device. The quantum conclusions, however, do not follow from that calculation. Eq. (3) is posited directly as the Hamiltonian, with no derivation of g^(m)_ij,kl from R_n, and Eqs. (5)-(7b) are assumed formulas whose consequences (longer T2', higher fidelity) are already contained in the assumptions. The author's self-citations [40,41] are used for the classical inductance and scattering problem, not for the quantum mapping, so they are not themselves the main circularity. The result is partial circularity: the full-wave data are independent, but the central performance claims reduce by construction to the assumed equations.

Assumptions & free parameters 6 free parameters · 6 assumptions · 0 invented entities

The paper's central performance claims depend on hand-tuned modulation parameters and on three posited formulas (Eq 3, Eq 5, Eq 6) that are not derived from the metasurface physics. The classical scattering model is inherited from the author's prior work. These are the main unexamined inputs.

free parameters (6)

ePhi_dc (DC flux bias) = 1.22, 1.2, 0.97, 0.95, 0.73 (per figure)
Hand-selected per target transition in Fig 5 and Fig 6; no optimization or independent constraint is shown.
ePhi_rf (RF modulation amplitude) = 0.23, 0.25, 0.2, 0.4, 0.73 (per figure)
Hand-selected to achieve the desired frequency conversion; no predictive rule is given.
d (metasurface thickness) = 0.4 lambda0, 0.26 lambda0, 0.3 lambda0
Chosen per scenario to produce the intended state transitions.
fs (modulation frequency) = 3 GHz, 6 GHz, 1.5 GHz
Chosen per scenario; affects the frequency channels and detuning Delta f.
gamma (space-time velocity ratio) = 1, 0.6, 0.5, 0.3 (per figure)
Hand-tuned for each transition in Fig 5; not derived or measured.
sigma (noise suppression bandwidth in Eq 6) = not specified
A free parameter controlling the claimed exponential noise reduction; no value or derivation is given.

assumptions (6)

ad hoc to paper Qubits are described by the standard Pauli Hamiltonian with nearest-neighbor couplings (Eq 1a) and, with the metasurface, by the polychromatic Hamiltonian (Eq 3) containing arbitrary multi-frequency couplings g^(m)_ij,kl.
The multi-frequency coupling is posited rather than derived from the qubit-metasurface interaction; it is the mathematical vehicle for the all-to-all claim.
ad hoc to paper Coherence time enhancement follows T'_2 = T2(1 + 2πDelta f/gamma) (Eq 5).
No derivation from noise models or the metasurface response; the formula encodes the claimed benefit.
ad hoc to paper Noise spectral density is suppressed as Seff(omega) = S0(omega) exp(-Delta omega^2 / 2 sigma^2) (Eq 6) with free bandwidth sigma.
The Gaussian suppression is assumed with no physical derivation; sigma is a free parameter.
domain assumption Fidelity of an entangled state decays as F(t) = exp(-t/T2) under Markovian decoherence.
A standard quantum-information result cited from refs [35-37] and applied to superconducting qubits.
domain assumption The space-time-modulated Josephson junction array inductance is Ls(I,z,t) = (Phi0/2pi I0) sec(ePhi_dc + ePhi_rf sin[kappa_s z - omega_s t + phi]) (Eq 8), taken from refs [40,41].
Accepted from prior work, not re-derived in this paper.
domain assumption Reflected field amplitudes R_n are obtained by imposing continuity of tangential electromagnetic fields at the metasurface boundaries (Eq 9).
The derivation is not shown; it relies on the author's previous scattering analysis.

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Cite this review

Pith. "Pith review of Space-Time-Coupled Qubits for Enhanced Superconducting Quantum Computing." pith.science (2026). https://pith.science/paper/VZMEOQVD

@misc{pith2026250116872,
  author       = {Pith},
  title        = {Pith review of: Space-Time-Coupled Qubits for Enhanced Superconducting Quantum Computing},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/VZMEOQVD}},
  note         = {Machine review of arXiv:2501.16872}
}

read the original abstract

The pursuit of scalable and robust quantum computing necessitates innovative approaches to overcome the inherent challenges of qubit connectivity, decoherence, and susceptibility to noise and crosstalk. Conventional monochromatic qubit coupling architectures, constrained by nearest-neighbor interactions and limited algorithmic flexibility, exacerbate these issues, hindering the realization of practical large-scale quantum processors. In this work, we introduce a paradigm leveraging a space-time-modulated cryogenic-compatible Josephson metasurface to enable polychromatic qubit coupling. This metasurface facilitates frequency-selective interactions, transforming nearest-neighbor connectivity into all-to-all qubit interactions, while significantly enhancing coherence, noise robustness, and entanglement fidelity. Our proposed approach capitalizes on the unique capabilities of space-time-modulated Josephson metasurfaces, including dynamic four-dimensional wave manipulation, nonreciprocal state transmission, and state-frequency conversion, to mediate multi-frequency qubit interactions. By isolating qubit couplings into distinct spectral channels, the cryogenic-compatible metasurface mitigates crosstalk and environmental decoherence, extending coherence times and preserving quantum state fidelity. Full-wave simulations and quantum performance analyses demonstrate a significant enhancement in the operational efficiency of a superconducting qubit array, showcasing improved connectivity, robustness, and entanglement stability. This study establishes the potential of space-time-modulated cryogenic-compatible Josephson metasurfaces as a transformative platform for next-generation quantum computing, addressing critical bottlenecks and paving the way for scalable, high-performance quantum processors.

Figures

Figures reproduced from arXiv: 2501.16872 by the authors.

**Figure 1.** FIG. 1. Schematic representation of space-time-modulated coupling between superconducting qubits, demonstrating energy [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗

**Figure 2.** FIG. 2. Illustration of the restricted functionality in con [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗

**Figure 3.** FIG. 3. Illustration of long-range, polychromatic entanglement within a qubit array enabled by a space-time-modulated [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗

Figures from the paper (3 more)

**Figure 4.** Figure 4: FIG. 4. Experimental setup for quantum circuit character [PITH_FULL_IMAGE:figures/full_fig_p007_4.png]

**Figure 5.** Figure 5: FIG. 5. Selective space-time coupling and frequency-state transitions of superconducting qubits mediated by a space-time [PITH_FULL_IMAGE:figures/full_fig_p009_5.png]

**Figure 6.** Figure 6: FIG. 6. Space-time coupling and quantum state transitions of eight superconducting qubits mediated by a space-time-modulated [PITH_FULL_IMAGE:figures/full_fig_p010_6.png]

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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Reference graph

Works this paper leans on

47 extracted references · 39 canonical work pages · cited by 1 Pith paper

[1]

This enhanced connectivity enables more efficient implementation of complex quantum algo- rithms, reducing the number of required gate operations and their associated errors

Enhanced connectivity and algorithm efficiency: The metasurface facilitates polychromatic interactions, transforming limited nearest-neighbor coupling into all- to-all connectivity. This enhanced connectivity enables more efficient implementation of complex quantum algo- rithms, reducing the number of required gate operations and their associated errors

work page
[2]

Improved coherence through frequency separation: Frequency-division multiplexing reduces crosstalk by iso- lating qubit interactions into distinct spectral channels, minimizing interference and preserving quantum state fi- delity

work page
[3]

Coherence time improvement: By mitigating noise and environmental decoherence through tailored coupling mechanisms, the metasurface extends qubit coherence times, allowing for longer and more reliable quantum computations

work page
[4]

Robustness against crosstalk and noise: The space- time modulation of the metasurface suppresses spurious interactions, enhancing the system’s overall noise immu- nity and enabling more precise qubit control

work page
[5]

This paper is organized as follows: Section II discusses the limitations of monochromatic qubit coupling and out- lines the theoretical framework for polychromatic inter- actions

Improved entanglement robustness: Polychromatic coupling stabilizes entangled states by reducing the im- pact of decoherence and cross-interference, critical for the performance of quantum error correction and multi-qubit operations. This paper is organized as follows: Section II discusses the limitations of monochromatic qubit coupling and out- lines the...

work page
[6]

In the monochromatic case (∆ ω = 0), gij,kl ̸= 0 only for adjacent qubits

Frequency-multiplexed interaction: Coupling occurs at multiple frequencies, enabling enhanced connectivity. In the monochromatic case (∆ ω = 0), gij,kl ̸= 0 only for adjacent qubits. However, in the polychromatic case, coupling is mediated by multiple harmonics, where g(m) ij,kl facilitates interactions between non-adjacent qubits. The introduction of enh...

work page
[7]

D. P. DiVincenzo, Quantum computation, Science 270, 255 (1995)

1995
[8]

T. D. Ladd, F. Jelezko, R. Laflamme, Y. Nakamura, C. Monroe, and J. L. O’Brien, Quantum computers, na- ture 464, 45 (2010)

work page 2010

Show all 47 references

[9]

A. W. Harrow and A. Montanaro, Quantum computa- tional supremacy, Nature 549, 203 (2017)

2017
[10]

J. M. Gambetta, J. M. Chow, and M. Steffen, Building logical qubits in a superconducting quantum computing system, npj quantum information 3, 2 (2017)

2017
[11]

Berlin, R

A. Berlin, R. T. D’Agnolo, S. A. Ellis, C. Nantista, J. Neilson, P. Schuster, S. Tantawi, N. Toro, and K. Zhou, Axion dark matter detection by superconducting res- onant frequency conversion, Journal of High Energy Physics 2020, 1 (2020)

2020
[12]

A. V. Dixit, S. Chakram, K. He, A. Agrawal, R. K. Naik, D. I. Schuster, and A. Chou, Searching for dark mat- ter with a superconducting qubit, Phys. Rev. Lett. 126, 141302 (2021)

2021
[13]

S. D. Bass and M. Doser, Quantum sensing for particle physics, Nat. Rev. Phys. , 1 (2024)

2024
[14]

S. C. Benjamin, Quantum computing without local con- trol of qubit-qubit interactions, Phys. Rev. Lett. 88, 017904 (2001)

2001
[15]

Holmes, S

A. Holmes, S. Johri, G. G. Guerreschi, J. S. Clarke, and A. Y. Matsuura, Impact of qubit connectivity on quan- tum algorithm performance, Quantum Science and Tech- nology 5, 025009 (2020)

2020
[16]

Y. He, J. Liu, C. Zhao, R. Huang, G. Dai, and W. Chen, Control system of superconducting quantum computers, Journal of Superconductivity and Novel Magnetism 35, 11 (2022)

2022
[17]

J. M. Martinis, K. B. Cooper, R. McDermott, M. Steffen, M. Ansmann, K. Osborn, K. Cicak, S. Oh, D. P. Pappas, R. W. Simmonds, et al., Decoherence in josephson qubits from dielectric loss, Physical review letters 95, 210503 (2005)

2005
[18]

McDermott, Materials origins of decoherence in super- conducting qubits, IEEE Transactions on Applied Super- conductivity 19, 2 (2009)

R. McDermott, Materials origins of decoherence in super- conducting qubits, IEEE Transactions on Applied Super- conductivity 19, 2 (2009)

2009
[19]

Mundada, G

P. Mundada, G. Zhang, T. Hazard, and A. Houck, Sup- pression of qubit crosstalk in a tunable coupling super- conducting circuit, Physical Review Applied 12, 054023 (2019)

2019
[20]

Tripathi, H

V. Tripathi, H. Chen, M. Khezri, K.-W. Yip, E. Levenson-Falk, and D. A. Lidar, Suppression of crosstalk in superconducting qubits using dynamical de- coupling, Physical Review Applied 18, 024068 (2022)

2022
[21]

Einstein, B

A. Einstein, B. Podolsky, and N. Rosen, Can quantum- mechanical description of physical reality be considered complete?, Phys. Rev. 47, 777 (1935)

1935
[22]

Horodecki, P

R. Horodecki, P. Horodecki, M. Horodecki, and K. Horodecki, Quantum entanglement, Rev. Mod. Phys. 81, 865 (2009)

2009
[23]

Erhard, M

M. Erhard, M. Krenn, and A. Zeilinger, Advances in high-dimensional quantum entanglement, Nature Re- views Physics 2, 365 (2020). 11

2020
[24]

Taravati and G

S. Taravati and G. V. Eleftheriades, Full-duplex non- reciprocal beam steering by time-modulated phase- gradient metasurfaces, Phys. Rev. Appl. 14, 014027 (2020)

2020
[25]

Taravati and G

S. Taravati and G. V. Eleftheriades, Full-duplex reflective beamsteering metasurface featuring magnetless nonrecip- rocal amplification, Nat. Commun. 14, 4414 (2021)

2021
[26]

Taravati and A

S. Taravati and A. A. Kishk, Space-time modulation: Principles and applications, IEEE Microw. Mag. 21, 30 (2020)

2020
[27]

Taravati and A

S. Taravati and A. A. Kishk, Advanced wave engineer- ing via obliquely illuminated space-time-modulated slab, IEEE Trans. Antennas Propagat. 67, 270 (2019)

2019
[28]

Taravati and G

S. Taravati and G. V. Eleftheriades, Microwave space- time-modulated metasurfaces, ACS Photonics 9, 305 (2022)

2022
[29]

Sisler, P

J. Sisler, P. Thureja, M. Y. Grajower, R. Sokhoyan, I. Huang, and H. A. Atwater, Electrically tunable space– time metasurfaces at optical frequencies, Nat. Nanotech- nol , 1 (2024)

2024
[30]

Taravati, Self-biased broadband magnet-free linear iso- lator based on one-way space-time coherency, Phys

S. Taravati, Self-biased broadband magnet-free linear iso- lator based on one-way space-time coherency, Phys. Rev. B 96, 235150 (2017)

2017
[31]

Taravati, Giant linear nonreciprocity, zero reflection, and zero band gap in equilibrated space-time-varying me- dia, Phys

S. Taravati, Giant linear nonreciprocity, zero reflection, and zero band gap in equilibrated space-time-varying me- dia, Phys. Rev. Appl. 9, 064012 (2018)

2018
[32]

Taravati and A

S. Taravati and A. A. Kishk, Dynamic modulation yields one-way beam splitting, Phys. Rev. B 99, 075101 (2019)

2019
[33]

Taravati and G

S. Taravati and G. V. Eleftheriades, Lightweight low- noise linear isolator integrating phase-and amplitude- engineered temporal loops, Adv. Mater. Technol , 2100674 (2021)

2021
[34]

Taravati, Spatiotemporal photon blockade for nonreciprocal quantum absorption, arXiv preprint arXiv:2409.08137 (2024)

S. Taravati, Spatiotemporal photon blockade for nonreciprocal quantum absorption, arXiv preprint arXiv:2409.08137 (2024)

2024 arXiv
[35]

Nagulu, A

A. Nagulu, A. Mekawy, M. Tymchenko, D. Sounas, H. Krishnaswamy, and A. Al` u, Synthetic helicoidal rota- tion of a quasielectrostatic ring resonator for ultrabroad- band magnet-free nonreciprocity, Physical Review Ap- plied 22, 064020 (2024)

2024
[36]

Taravati, Aperiodic space-time modulation for pure frequency mixing, Phys

S. Taravati, Aperiodic space-time modulation for pure frequency mixing, Phys. Rev. B 97, 115131 (2018)

2018
[37]

Taravati and G

S. Taravati and G. V. Eleftheriades, Pure and linear frequency-conversion temporal metasurface, Phys. Rev. Appl. 15, 064011 (2021)

2021
[38]

Taravati and G

S. Taravati and G. V. Eleftheriades, Space-time medium functions as a perfect antenna-mixer-amplifier transceiver, Phys. Rev. Appl. 14, 054017 (2020)

2020
[39]

Taravati and G

S. Taravati and G. V. Eleftheriades, Generalized space- time periodic diffraction gratings: Theory and applica- tions, Phys. Rev. Appl. 12, 024026 (2019)

2019
[40]

Taravati and G

S. Taravati and G. V. Eleftheriades, 4D wave transforma- tions enabled by space-time metasurfaces: Foundations and illustrative examples, IEEE Antennas Propag. Mag. 65, 61 (2023)

2023
[41]

J. Liu, W. Wang, C. Zhang, Q. Niu, and B. Li, Fidelity for the quantum evolution of a bose-einstein conden- sate, Physical Review A—Atomic, Molecular, and Op- tical Physics 72, 063623 (2005)

2005
[42]

W.-g. Wang, G. Casati, B. Li, and T. Prosen, Uniform semiclassical approach to fidelity decay in the deep lya- punov regime, Physical Review E—Statistical, Nonlin- ear, and Soft Matter Physics 71, 037202 (2005)

2005
[43]

Silvestrov, J

P. Silvestrov, J. Tworzyd lo, and C. Beenakker, Hypersen- sitivity to perturbations of quantum-chaotic wave-packet dynamics, Physical Review E 67, 025204 (2003)

2003
[44]

M. A. Nielsen and I. L. Chuang, Quantum computation and quantum information (Cambridge university press, 2010)

2010
[45]

Preskill, Quantum computing in the nisq era and be- yond, Quantum 2, 79 (2018)

J. Preskill, Quantum computing in the nisq era and be- yond, Quantum 2, 79 (2018)

2018
[46]

Taravati, Efficient nonreciprocal frequency conversion with space-time josephson junction metasurfaces, in 2024 54th European Microwave Conference (EuMC)(IEEE,

S. Taravati, Efficient nonreciprocal frequency conversion with space-time josephson junction metasurfaces, in 2024 54th European Microwave Conference (EuMC)(IEEE,

2024
[47]

Taravati, Light interaction with a space-time- modulated josephson junction array and application to angular-frequency beam multiplexing, arXiv preprint arXiv:2501.01842 (2025)

S. Taravati, Light interaction with a space-time- modulated josephson junction array and application to angular-frequency beam multiplexing, arXiv preprint arXiv:2501.01842 (2025)

2025 arXiv

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.

[1] [1]

This enhanced connectivity enables more efficient implementation of complex quantum algo- rithms, reducing the number of required gate operations and their associated errors

Enhanced connectivity and algorithm efficiency: The metasurface facilitates polychromatic interactions, transforming limited nearest-neighbor coupling into all- to-all connectivity. This enhanced connectivity enables more efficient implementation of complex quantum algo- rithms, reducing the number of required gate operations and their associated errors

work page

[2] [2]

Improved coherence through frequency separation: Frequency-division multiplexing reduces crosstalk by iso- lating qubit interactions into distinct spectral channels, minimizing interference and preserving quantum state fi- delity

work page

[3] [3]

Coherence time improvement: By mitigating noise and environmental decoherence through tailored coupling mechanisms, the metasurface extends qubit coherence times, allowing for longer and more reliable quantum computations

work page

[4] [4]

Robustness against crosstalk and noise: The space- time modulation of the metasurface suppresses spurious interactions, enhancing the system’s overall noise immu- nity and enabling more precise qubit control

work page

[5] [5]

This paper is organized as follows: Section II discusses the limitations of monochromatic qubit coupling and out- lines the theoretical framework for polychromatic inter- actions

Improved entanglement robustness: Polychromatic coupling stabilizes entangled states by reducing the im- pact of decoherence and cross-interference, critical for the performance of quantum error correction and multi-qubit operations. This paper is organized as follows: Section II discusses the limitations of monochromatic qubit coupling and out- lines the...

work page

[6] [6]

In the monochromatic case (∆ ω = 0), gij,kl ̸= 0 only for adjacent qubits

Frequency-multiplexed interaction: Coupling occurs at multiple frequencies, enabling enhanced connectivity. In the monochromatic case (∆ ω = 0), gij,kl ̸= 0 only for adjacent qubits. However, in the polychromatic case, coupling is mediated by multiple harmonics, where g(m) ij,kl facilitates interactions between non-adjacent qubits. The introduction of enh...

work page

[7] [7]

D. P. DiVincenzo, Quantum computation, Science 270, 255 (1995)

1995

[8] [8]

T. D. Ladd, F. Jelezko, R. Laflamme, Y. Nakamura, C. Monroe, and J. L. O’Brien, Quantum computers, na- ture 464, 45 (2010)

work page 2010